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Purpose: The cardinal symptoms of carpal tunnel syndrome (CTS) include pain in the affected hand(s). The median/second lumbrical nerve (Med2ndL) seems relatively preserved in severe CTS, with previous small studies suggesting its value in electromyogram to localize a median neuropathy to the wrist when both initial routine sensory and thenar motor responses are absent., Methods: This is a retrospective analysis of 208 hands in 183 patients with electrophysiologically markedly severe CTS (absent routine sensory and thenar motor median responses) who underwent stimulation of both the Med2ndL and ulnar/second dorsal interosseous (Uln2ndDIn) motor nerves. A Med2ndL distal latency of ≥ 0.5 milliseconds when compared with the Uln2ndDIn supported the diagnosis of CTS. The presence or absence of hand pain was recorded if these data were available., Results: Some 83.7% of hands (172/208) in 183 patients with markedly severe CTS had preservation of the Med2ndL meeting criteria for CTS. In those with pain data available, 77.1% (81/105) of hands had no pain. Of those 105 hands, 87 had preservation of the Med2ndL with 79.3% (69/87) demonstrating no pain., Conclusions: This is a large study that demonstrates the relative preservation of the Med2ndL response in markedly severe CTS. Assessment of the Med2ndL should be considered to electrophysiologically support CTS when routine sensory and thenar motor responses are absent. In addition, most patients with electrophysiologically markedly severe CTS had no pain., Competing Interests: The authors have no funding or conflicts of interest to disclose., (Copyright © 2021 by the American Clinical Neurophysiology Society.)

Ultrasound (US) is commonly used to evaluate ulnar nerve instability (UNI) and snapping of the medial head of the triceps brachii muscle (ST). We aimed to determine the diagnostic accuracy of US in evaluating UNI, through cadaveric dissection, and to evaluate the US features and relationships of UNI and ST according to elbow flexion. Dynamic US was performed with elbow extension, 90° flexion, and full flexion positions on 18 elbows from 9 fresh cadavers. UNI was classified into N (normal), S (subluxation), and D (dislocation) types. On US exams, the following findings and parameters were evaluated: the presence of UNI and ST; the horizontal distance from the apex of the medial epicondyle (ME) to the margins of the UN and medial head of the triceps brachii muscle (ME_UN and ME_TB, respectively); cross-sectional area and flattening ratio (FR) of UN. After US, all cadavers were dissected to expose the UN and TB, and elbow flexion and extension were simulated to confirm UNI and ST. The gross anatomic findings of UNI and ST were consistent with the US findings. In extension and 90° flexion positions, all cases were type N. In full flexion position, types N and S occurred in 10 (56%) and 8 (44%) elbows, respectively. FR and ME_UN in 90° flexion position, FR, ME_UN, and ME_TB in full flexion position differed significantly between types S and N. Positive correlations were found between ME_UN and ME_TB in 90° flexion and full flexion positions. Dynamic US accurately assessed UNI and ST. UNI was positively correlated to medial TB movement., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc.)

Purpose: Ulnar sensory palmar crossover to digit three (D3), the Berrettini anastomosis, is measurable in routine electrodiagnostic nerve conduction studies. The crossover is reported as occurring in 60% of anatomic dissections, but the frequency of measurable ulnar crossover to D3 and its potential as a nerve conduction pitfall is not established. The purpose of this article was to present descriptive statistics regarding the frequency of measurable Berrettini anastomosis in nerve conduction studies., Methods: A retrospective chart review and data analysis was completed on 248 patients representing 411 extremities with a main outcome measure of ulnar sensory stimulated nerve conduction simultaneous waveform recording on D3 and digit four (D4). Consistent electrodiagnostic technique with waveform recording data analysis in a private practice and independent university waveform verification was completed on sequential patients referred for upper extremity electrodiagnostic testing., Results: Measurable ulnar stimulated D3 sensory nerve action potentials were demonstrated in 34% of patients with amplitudes of 27%, the simultaneously recorded corresponding ulnar D4 amplitudes representing electrophysiological evidence of ulnar sensory crossover., Conclusions: The Berrettini anastomosis can frequently be seen as a small amplitude sensory nerve action potential response, but at times can be observed with an amplitude greater than 10 μV. It is possible that patients with an absent or significantly delayed median nerve response may have simultaneous inadvertent spread of stimulus to ulnar axons measurable on D3 that may be interpreted as a falsely normal response. All electromyographers need to be aware of this potential pitfall.

This 2-group study was carried out to determine the inter-practitioner difference of nerve conduction studies with standardized techniques.56 normal subjects of 19 to 49 year-old were recruited, 29, and 27 in the 2 labs respectively. Tests were carried out unilaterally on: 5 motor nerve distal latency, conduction velocities (MNCV) and minimum latency of F wave, 3 sensory nerves with negative amplitude, onset, and peak distal latency, sensory nerve distal latency.T-test disclosed 4(15.4%) attributes with statistical significance (P < .05). They were 2 of 4 (50%) compound motor action potentials, which were ulnar and tibial nerve, and 2 of 6 (33.3%) MNCVs, which were elbow-to-wrist MNCV of median nerve and cross-fibula MNCV of peroneal nerve. No differences were disclosed in motor nerve distal latencys, minimum latency of F waves and all sensory attributes.Inconsistency pattern of certain attributes were found. This could be explained with the insufficient definition of related techniques.

Background: Objective sensory testing is a critical component of the physical examination in children as they may be unable to communicate whether or not numbness is present. The purpose of this study was to determine at what age objective sensory tests could reliably be performed., Methods: Normal, uninjured participants aged 2 to 17 years were enrolled in the study. Monofilament and static/moving 2-point discrimination tests were performed bilaterally assessing the median, ulnar, and radial nerves. Performance scores were recorded using the monofilament size and 2-point discrimination distance. Statistical analysis was performed utilizing univariable linear regression, 1-way ANOVA, and Welch t test., Results: A total of 396 hands were tested utilizing the Semmes-Weinstein monofilament and static/moving 2-point discrimination tests. For the monofilament test, 27% of 3-year-olds, 83% of 4-year-olds, and all participants 5 years of age and older were capable of performing the monofilament test. The average monofilament scores were 2.874, 2.868, and 3.043 for the ulnar, median, and radial nerves, respectively, with no correlation with advancing age present. The ulnar and median nerve distributions were more sensitive than the radial nerve distribution (P<0.001).For 2-point discrimination tests, 33% of 4-year-olds, 61% of 5-year-olds, 88% of 6-year-olds, 95% of 7- and 8-year-olds, and all participants 9 years and older were capable of performing the static/moving 2-point discrimination tests. The average static 2-point discrimination scores were 3.348, 2.806, and 9.637 mm for the ulnar, median, and radial nerves, respectively. The average moving 2-point discrimination scores were 2.977, 2.483, and 8.506 mm for the ulnar, median, and radial nerves, respectively. There was no correlation between advancing age and performance scores. Children are the most sensitive in the median, then ulnar, and then radial nerve distribution (P<0.001). Better discrimination is present between 2 moving points than static points (P<0.001)., Conclusions: Objective threshold testing utilizing a monofilament can reliably be performed in the vast majority of children aged 4 years and above, whereas density testing utilizing 2-point discrimination can reliably be performed in the vast majority of children aged 6 years and above., Level of Evidence: Level II.

The aim of this study was to evaluate the influence of unilateral reduction of afferent input on the 'neural coupling' mechanism during cooperative hand movements. This 'neural coupling' is reflected in the task-specific appearance of contralateral reflex responses in forearm muscles to unilateral arm nerve stimulation. Sensory input from the right hand was reduced by ischemic nerve block at the right wrist. Ipsilateral and contralateral reflex responses elicited by stimulation of the ulnar nerve either at the left or the right wrist proximal to the nerve block were recorded in forearm extensors during the performance of cooperative hand movements. During ischemia of the right hand, a significant difference was found in the magnitude of the contralateral responses, that is, contralateral reflex responses in the right arm were significantly higher compared with the left arm (P=0.04). Ipsilateral reflex responses were not affected by ischemic nerve block. The reduced afference from the ischemic hand during cooperative hand movements is assumed to weaken the activity in ipsilateral pathways involved in the neural coupling mechanism. Consequently, a shift in the interhemispheric balance might lead to the relative increase and decrease in the contralateral responses to left and right nerve stimulation, respectively. The study provides novel information on the involvement of ipsilateral hemispheres in the performance of cooperative hand movements.

Purpose: F waves identical in latency, size, and shape, known as repeater F waves, have been observed occasionally in normal motor conduction recordings. The purpose of this study was to examine the occurrence and characteristics of repeater F waves in healthy subjects under different testing conditions, aiming to selectively excite lower and higher threshold motor fibers., Methods: Sessions of 40 traces were recorded from the ulnar nerve in 12 volunteers, applying/using supramaximal, submaximal stimuli (intensity able to elicit 30% and 60% of the maximum compound muscle action potential amplitude), and a collision technique. Repeater F waves were identified and their numbers and relative frequency were estimated. For this purpose, a custom-designed software program was developed, to avoid misjudgments of simple visual inspection., Results: Repeater occurrence was significantly higher using 30% submaximal intensity compared with the standard supramaximal stimulation. There was an inverse significant association between repeater index and overall F wave quantity. Repeaters' latency, amplitude, and duration measurements were within the ranges of the nonrepeaters., Conclusions: We herein showed that in healthy subjects the presence of repeater F waves might increase, when stimulation conditions other than standard single, supramaximal impulses were used. The frequency of repeaters was dependent on the overall F wave persistence, but there was no evidence to support a relationship with the type of motoneurons that was preferentially stimulated.

Objective: The purpose of this study was to obtain data on interrater repeatability of the motor nerve conduction velocity (NCV) of the ulnar nerve of different segments, ulnar distal motor latency (DML), and compound muscle action potential (CMAP) amplitudes., Design: Twenty-four healthy volunteers were examined in consecutive order. Ulnar motor NCV of different segments, ulnar DML, and CMAP amplitudes were determined. Based on a randomization list of various combinations and sequences, 1 of 3 examiners performed the first measurement. A second examiner repeated the evaluation within half an hour., Results: There were no significant differences between the first and second measurements for all parameters. For the ulnar motor NCV of the different segments, the intraclass correlation coefficient (ICC) ranged from 0.38 to 0.51, and the coefficient of repeatability (CR) ranged from 8.0 to 11.6 m/s. For the ulnar DML, the ICC was 0.44, and the CR was 0.49 millisecond. For the CMAP amplitudes at the different stimulation sites, the ICC ranged from 0.53 to 0.76, and the CR ranged from 1.5 to 2.3 mV., Conclusions: A moderate amount of interrater variability of the ulnar motor NCV must be taken into account. Compared with the CMAP amplitudes, the interrater repeatability of the ulnar motor NCV is poorer.

Background: There are few studies supporting supercharge end-to-side nerve transfer for high ulnar nerve injury. The current study hypothesized that patients with a supercharge end-to-side anterior interosseous nerve-to-ulnar motor nerve transfer would demonstrate superior return of intrinsic function compared with conventional treatment only., Methods: A retrospective matched-cohort study matched supercharge end-to-side transfer patients based on age, level of injury, and mechanism to ulnar nerve injury patients who did not have the transfer. The primary outcome was return of ulnar intrinsic function, based on clinical examination and/or electromyography. Dichotomous and continuous variables were compared with Fisher's exact and t tests, respectively., Results: Thirteen supercharge end-to-side patients were identified (>1 year follow-up). The average age of both cohorts was 35 years. Ulnar nerve transection above the proximal third of the forearm represented 54 percent of patients; compressive injuries represented 46 percent. Eleven supercharge end-to-side transfer patients (84 percent) demonstrated intrinsic function recovery compared with five (38 percent) non-supercharge end-to-side patients (p < 0.05). Average time to initial motor recovery was similar between the two groups (supercharge end-to-side, 2.9 months; non-supercharge end-to-side, 3.8 months; p > 0.2). Intrinsic function return was more likely following nerve transection with the supercharge end-to-side procedure (85 percent versus 14 percent; p = 0.03), whereas compression injuries had comparable intrinsic function return regardless of the supercharge end-to-side transfer (67 percent versus 67 percent; p = 1.0)., Conclusions: This matched cohort study demonstrates that the supercharge end-to-side transfer results in increased ulnar intrinsic reinnervation following ulnar nerve injury. This finding may be most relevant following transection injuries. Improved outcomes associated with supercharge end-to-side and ulnar nerve repair warrant further investigation., Clinical Question/level of Evidence: Therapeutic, III.

Purpose: Threshold tracking is a new noninvasive approach for detecting axonal excitability changes in vivo. In this study, the authors compared the excitability indices of motor and sensory axons of median and ulnar nerves to determine whether the two nerves behave in a similar or a noninterchangeable way. They also examined whether age affects these indices., Methods: Seventy normal subjects aged 22-70 years (mean, 36.7 ± 12.5 years) were recruited. Multiple excitability indices were measured in both motor and sensory axons from median and ulnar nerves., Results: The threshold and rheobase were significantly higher for the ulnar motor axons recorded at the first dorsal interosseous muscle than for the median motor axons at the abductor pollicis brevis muscle. In contrast, the strength-duration time constant was decreased, threshold electrotonus reduction (in both depolarizing and hyperpolarizing directions) was significantly smaller, I/V slope was decreased, and subexcitability was reduced for the ulnar motor axons. Excitability indices measured in the sensory axons of both nerves were not overtly different. In R-square analysis, age had a homogeneous influence on sensory axon excitability but heterogeneous influence on motor axon excitability., Conclusions: The excitability indices may be interchangeable for sensory axons but not motor axons. The authors therefore recommend recording motor axonal excitability in various muscle groups rather than a single muscle group.

Purpose: The authors have observed that in healthy people, the Ulnar wrist-to-first dorsal interosseous distal motor latency does not differ significantly compared with median wrist-to-abductor pollicis brevis distal motor latency. The aim of our study was to investigate whether the difference between these two latencies can be used as a screening tool for diagnosing carpal tunnel syndrome and how this technique compares with other established techniques., Methods: The study was set up as a prospective observational study. As gold standard for the clinical diagnosis of carpal tunnel syndrome, the authors used the opinion of two neurologists who independently examined the patients. A third neurologist, also independently, performed the electrophysiological study., Results: Eighty-four subjects, 42 patients and 42 age- and sex-matched controls, participated in the study. Among all subjects using a receiver operating characteristic curve analysis, the area under the curve was 0.924 (95% CI, 0.857-0.991; SE, 0.034; P < 0.001). To detect carpal tunnel syndrome, at a cutoff score of equal to or greater than 0.575 milliseconds, our technique showed a sensitivity of 91%, a specificity of 93%, a positive predictive value of 93%, and a negative predictive value of 91%. Compared with other "classical" techniques, our technique showed better area under the receiver operating characteristic curve and better Youden index., Conclusions: The median wrist-to-abductor pollicis brevis motor latency minus ulnar wrist-to-first dorsal interosseous motor latency may be used as a novel rapid screening tool of patients suffering from carpal tunnel syndrome.

Background: The position of the ulnar nerve relative to the medial epicondyle in healthy children was determined with a high-resolution ultrasonography with elbow flexion, forearm pronation, and supination maneuvers which are commonly employed during reduction of the supracondylar humerus fractures., Methods: Healthy children aged between 4 and 12 years were enrolled in this study. Both elbows of the children were evaluated with a high-resolution sonography device with gradual flexion of the elbow, whereas the forearm is alternately in pronation and supination. The medial epicondyle-ulnar nerve distance was measured with the various positions of the elbow and the forearm. One-way analysis of variance was used to analyze the differences of medial epicondyle-ulnar nerve distance at different elbow flexion angles and forearm supination-pronation positions. Paried t test was used to compare the differences between the age and sex of the children., Results: Twelve female and 26 male children (76 elbows) with a mean age of 8.36 years were included in the study. Ulnar nerve was translated anteriorly through the medial epicondyle with increasing elbow flexion. The mean medial epicondyle-ulnar nerve distance that was 3.7 mm in an extended elbow decreased to 1.1 mm with full elbow flexion. The difference was statistically significant (P<0.0001). Presence of the forearm in either supination or pronation did not produce a statistically significant difference. The age and sex of the children did not produce a statistically significance difference in medial epicondyle-ulnar nerve distance., Conclusions: Flexion of the elbow brings the ulnar nerve to a close proximity to the medial epicondyle independent of forearm pronation and supination in healthy children. The decrement of the medial epicondyle-ulnar nerve distance up to 1.1 mm in a fully flexed elbow might be a factor that endangers the nerve during medial pinning in supracondylar humerus fractures., Level of Evidence: Level I-diagnostic studies.

The period between migraine attacks is characterized by paradoxical responses to repetitive sensory and transcranial magnetic stimulation (TMS). Abnormal long-term cortical functional plasticity may play a role and can be assessed experimentally by paired associative stimulation (PAS), in which somatosensory peripheral nerve stimuli are followed by TMS of the motor cortex. Changes in motor-evoked potential (MEP) amplitudes were recorded in 16 migraine without aura patients (MO) and 15 healthy volunteers (HV) before and after PAS, which consisted of 90 peripheral electrical right ulnar nerve stimulations and subsequent TMS pulses over the first dorsal interosseous (FDI) muscle activation site with a delay of 10 ms (excitability depressing) or 25 ms (excitability enhancing). As a control experiment of the 31 subjects studied, 8 (4 MO and 4 HV) also underwent PAS10 earlier, the recording of somatosensory high-frequency oscillations (HFOs) reflecting thalamocortical activation (early HFOs). Although PAS10 reduced MEP amplitudes in HV (-17.7%), it significantly increased amplitudes in MO (+35.9%). Although in HV MEP amplitudes were significantly potentiated (+55.1) after PAS25, only a slight, nonsignificant increase was observed in MO (+18.8%). In the control experiment, performed on 8 subjects pooled together, Pearson's correlation showed an inverse relationship between the percentage of MEP amplitude changes after PAS10 and early HFO amplitudes (r=-0.81; P=.01). Because we observed that the more deficient the long-term PAS-induced change, the more the thalamocortical activation decreased, we hypothesize that the abnormalities in long-term cortical plasticity observed in the interictal period between migraine episodes could be due to altered thalamic control., (Copyright © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.)

Anatomic variation and susceptibility for injuries depending on gender were described for the ulnar nerve. The aim of this study was to investigate the association between gender and ulnar never motor conductance and the influence of sidedness for this association. Study was conducted as a retrospective study using nerve conduction study data of ulnar nerve of 2,526 patients. Influences of age, gender, and sidedness on ulnar never motor conduction velocity (UMV) were investigated. Regression analysis was conducted to compare the relationship between UMV and age. Regression was significantly higher in males (-0.253 vs. -0.113), suggesting higher influence of age on UMV in males than in females. When analyzing right and left sides separately, influence of age on UMV is higher in males (-0.286 vs. -0.109) only in right side. Multiple regression analysis was done comparing the influence of age, gender, and sidedness on UMV, and it found that the order of influence is gender, age, and sidedness (Beta values 0.153, -0.140, and 0.029). Ulnar nerve motor conductance depends on gender, age, and sidedness. Males are having lower UMV than females. Age-dependant change of UMV is more prominent in males than in females and is more prominent in right hand than in left hand in males.

Purpose: Muscle twitch threshold has been used to determine optimal stimulus intensity for somatosensory evoked potentials but neuromuscular blockade precludes the use of muscle twitch during surgery. Accordingly, nerve action potential (NAP) amplitude was investigated as a surrogate to muscle twitch., Methods: The ulnar and tibial nerves were stimulated at the wrist and ankle, respectively, in 27 patients undergoing spine and brain surgery. After neuromuscular blockade was gone, the stimulus intensity for just maximal NAP amplitude recorded from Erb's point and the popliteal fossa was compared with the stimulus intensity for hypothenar and plantar foot muscle twitch threshold (times two), respectively (Wilcoxon matched pairs test)., Results: There was no significant difference between stimulus intensity for just maximal Erb's point and popliteal fossa NAP amplitude when compared with stimulus intensity for hypothenar and plantar foot twitch threshold (times two), respectively. Eight patients required more than twitch intensity (times two) to obtain maximum NAP., Conclusions: The NAP amplitude may be used to determine optimal somatosensory evoked potential stimulus intensity when muscle twitch is not visible. This method should improve the success of intraoperative somatosensory evoked potential monitoring and decrease erroneous interpretation.

Effects of low-threshold afferents of hand muscles innervated by the ulnar nerve on an excitability of the extensor carpi radialis (ECR) motoneurone pool in humans were examined using an electromyogram-averaging (EMG-A) technique. Changes of EMG-A of ECR exhibiting 10% of the maximum contraction by electrical stimulation to the ulnar nerve at the wrist (ES-UN) and mechanical stimulation to the hypothenar muscles (MS-HTM) and first dorsal interosseus (MS-FDI) were evaluated in eight normal human subjects. The ES-UN with the intensity immediately below the motor threshold and MS-HTM and -FDI with the intensity below the threshold of the tendon(T)-reflex were delivered. Early and significant peaks in EMG-A were produced by ES-UN, MS-HTM, and MS-FDI in eight of eight subjects. The mean amplitudes of the peaks by ES-UN, MS-HTM, and MS-FDI were, respectively, 121.9%, 139.3%, and 149.9% of the control EMG (100%). The difference between latencies of the peaks by ES-UN and MS-HTM, and ES-UN and MS-FDI was almost equivalent to that of the Hoffmann(H)- and T-reflexes of HTM and FDI, respectively. The peaks by ES-UN, MS-HTM, and MS-FDI diminished with tonic vibration stimulation (TVS) to HTM and FDI, respectively. These findings suggest that group Ia afferents of the hand muscles facilitate the ECR motoneurone pool.

Carpal tunnel syndrome (CTS) is the most common nerve entrapment syndrome. Electromyogram (EMG) is beneficial in supporting the diagnosis of CTS. We compared standard nerve conduction studies of EMG with median and ulnar motor nerve conduction studies from recordings of second lumbrical and interosseal muscles in supporting the diagnosis of CTS. In this study, a total of 242 patients were included, and a total of 375 hands were involved. Electrophysiologic CTSs were diagnosed in 283 hands of 161 patients. A significant association between second lumbrical-interosseal distal motor latency difference (2LI-MDLD) and CTS was found in this study. Statistically, every 0.1 increment in the 2LI-MDLD value was observed to increase the risk of disease by 1.74. When a cut-off of ≥ 0.5 for 2LI-MDLD is taken for predicting CTS, the sensitivity of the test is found to be 89.4% and specificity 84.4%. When the cut-off value for motor distal latency of second lumbrical of the median nerve (2L-MDL) was taken as ≥ 3.15 milliseconds in the diagnosis of CTS, the sensitivity of the test was 87.3%, and specificity 70.7%. Previous reports and our findings suggest that in CTS diagnosis, not only 2LI-MDLD value but also 2L-MDL value are easy and rapidly obtainable and offer additional information in very severe cases where compound muscle action potentials (CMAP) cannot be recorded from the abductor pollicis brevis (APB) muscle.

Interpretation of neurographic data in follow-up studies of patients with neuromuscular disease is sometimes challenging because of the expected variability in repeated tests. In this study, we explored whether the interexaminer variability of the compound motor action potential (CMAP) amplitude is reduced if the examiner is guided by the previously taken photographs of the position of the recording electrodes. The CMAPs were recorded from 20 subjects by unilateral distal stimulation of the median, ulnar, peroneal, and tibial nerve by 4 different technicians. All the subjects were examined on 2 occasions (∼1 week apart). On the first occasion, the technicians recorded the CMAP values according to routine protocols. On the second occasion, the technicians had additional guidance from photographs displaying the recording electrode positions from the first study. The CMAP coefficient of variation (CoV) was calculated for each nerve examined by the four technicians. Differences in CoV between the two types of tests (i.e., with or without photographs) were evaluated. When the examiners were guided by the photographs during electrode application, the CMAP CoV for the tibial innervated abductor hallucis (AH) muscle was reduced (P = 0.02) from 18.5% to 13%. There were, however, no significant reductions in CoV for the abductor pollicis brevis (APB, P = 0.23, median nerve), abductor digiti minimi (P = 0.37, ulnar nerve), or extensor digitorum brevis (EDB, P = 0.15, peroneal nerve) muscles. Photographic documentation of the CMAP recording electrodes seems to have a limited overall effect on interexaminer variability in a subsequent study.

Background: Reversal of residual neuromuscular blockade by acetylcholinesterase inhibitors (e.g., neostigmine) improves respiratory function. However, neostigmine may also impair muscle strength. We hypothesized that neostigmine administered after recovery of the train-of-four (TOF) ratio impairs upper airway integrity and genioglossus muscle function., Methods: We measured, in 10 healthy male volunteers, epiglottic and nasal mask pressures, genioglossus electromyogram, air flow, respiratory timing, and changes in lung volume before, during (TOF ratio: 0.5), and after recovery of the TOF ratio to unity, and after administration of neostigmine 0.03 mg/kg IV (with glycopyrrolate 0.0075 mg/kg). Upper airway critical closing pressure (Pcrit) was calculated from flow-limited breaths during random pharyngeal negative pressure challenges., Results: Pcrit increased significantly after administration of neostigmine/glycopyrrolate compared with both TOF recovery (mean ± SD, by 27 ± 21%; P = 0.02) and baseline (by 38 ± 17%; P = 0.002). In parallel, phasic genioglossus activity evoked by negative pharyngeal pressure decreased (by 37 ± 29%, P = 0.005) compared with recovery, almost to a level observed at a TOF ratio of 0.5. Lung volume, respiratory timing, tidal volume, and minute ventilation remained unchanged after neostigmine/glycopyrrolate injection., Conclusion: Neostigmine/glycopyrrolate, when administered after recovery from neuromuscular block, increases upper airway collapsibility and impairs genioglossus muscle activation in response to negative pharyngeal pressure. Reversal with acetylcholinesterase inhibitors may be undesirable in the absence of neuromuscular blockade.

Background: Nerve stimulation and ultrasound guidance are the most popular techniques for peripheral nerve blocks. However, the minimum effective anesthetic volume (MEAV) in selected nerves for both techniques and the consequences of decreasing the local anesthetic volume on the pharmacodynamic characteristics of nerve block remain unstudied. We designed a randomized, double-blind controlled comparison between neurostimulation and ultrasound guidance to estimate the MEAV of 1.5% mepivacaine and pharmacodynamics in median and ulnar nerve blocks., Methods: Patients scheduled for carpal tunnel release were randomized to ultrasound guidance (UG) or neurostimulation (NS) groups. A step-up/step-down study model (Dixon method) was used to determine the MEAV with nonprobability sequential dosing based on the outcome of the previous patient. The starting dose of 1.5% mepivacaine was 13 and 11 mL for median and ulnar nerves at the humeral canal. Block success/failure resulted in a decrease/increase of 2 mL. A blinded physician assessed sensory blockade at 2-minute intervals for 20 minutes. Block onset time and duration were noted., Results: The MEAV50 (SD) of the median nerve was lower in the UG group 2 (0.1) mL (95% confidence interval [CI] = [1, 96] to [2, 04]) than in the NS group 4 (3.8) mL (95% CI = [2, 4] to [5, 6]) (P = 0.017). There was no difference for the ulnar nerve between UG group 2 (0.1) mL (95% CI = [1, 96] to [2, 04]) and NS group 2.4 (0.6) mL (95% CI = [2, 1] to [2, 7]). The duration of sensory blockade was significantly correlated to local anesthetic volume, but onset time was not modified., Conclusion: Ultrasound guidance selectively provided a 50% reduction in the MEAV of mepivacaine 1.5% for median nerve sensory blockade in comparison with neurostimulation. Decreasing the local anesthetic volume can decrease sensory block duration but not onset time.

Introduction: In this prospective, randomized, double-blind study, we compared the effectiveness and time efficiency of perioperative axillary blocks performed via 2 different techniques, 1 involving 2 and the other 4 separate skin punctures., Methods: One hundred twenty patients undergoing upper limb surgery were randomized to receive either (1) an axillary brachial plexus block involving 2 injections, with 30 mL local anesthetic injected posterior to the axillary artery (with redirection, as needed, to achieve circumferential spread), plus 10 mL local anesthetic to the musculocutaneous nerve, guided by ultrasound (group 1, n = 56); or (2) 4 separate 10-mL injections to the median, ulnar, radial, and musculocutaneous nerves, using a combined ultrasound and neurostimulation technique (group 2, n = 58). All patients received 40 mL of 0.5% ropivacaine with 1:400,000 epinephrine. The primary outcome was the success rate of the block, defined as anesthesia adequate for surgery. Secondary outcomes were the time to administer the block, time to the onset of motor-sensory block, time to surgical readiness, and incidence of adverse events., Results: The 2-injection technique was slightly faster to administer (8 vs 11 minutes, P = 0.003). The mean nerve block score was slightly higher for the 4-injection group at the 10-, 15-, 20-, and 30-minute time points, but the cumulative percentages of blocks having taken effect were not significantly different over these time points, at 0.0%, 5.4%, 12.5%, and 37.5% among those who had received a 2-injection block versus 6.9%, 10.4%, 19.0%, and 48.3%, respectively, with the 4-injection block (P = 0.20). There was no difference in the percentage of patients with complete block by 30 minutes (32.1% vs 37.5%, P = 0.55) or in final block success rates (89.3% vs 87.9%, P = 0.99)., Conclusions: An ultrasound-guided 2-injection axillary block may be as effective as, and more time efficient than, a 4-injection technique.

Current electrodiagnostic studies for Ulnar nerve mononeuropathy at the elbow have substandard sensitivity and specificity. Reference values for a novel, screening electrodiagnostic test for ulnar nerve mononeuropathy at the elbow were obtained bilaterally from 72 subjects without any upper extremity signs or symptoms. The test used two, 3-cm straight line distances, one proximal, and one distal to the medial epicondyle to avoid a curvilinear measurement. The mean conduction times (CTE) were 1.16 +/- 0.16 milliseconds, 1.23 +/- 0.18 milliseconds, 1.33 +/- 0.24 milliseconds, for subjects 20 to 40, 40 to 60, and >60 years old, respectively. A CTE >1.50 milliseconds, >1.60 milliseconds, and >1.80 milliseconds for each age group would be considered abnormal conferring 98% specificity. The median side-to-side difference of CTE (CTE-diff) was 0.10 milliseconds with a range of 0.00 to 0.55 milliseconds. A CTE-diff >0.45 milliseconds has a specificity of 97%. Potential advantages to this method include straight-line measurement distances to reduce experimental error, and a distance less than 10 cm to improve lesion detection.

Background: Many studies have indicated that acceleromyography and mechanomyography cannot be used interchangeably. To improve the agreement between the two methods, it has been suggested to use a preload and to refer all train-of-four (TOF) ratios to the control TOF (normalization) when using acceleromyography. The first purpose of this study was to test whether a preload applied to acceleromyography would increase the precision and the agreement with mechanomyography. The second purpose was to evaluate whether normalization would improve the agreement with mechanomyography., Methods: Sixty patients were randomized to acceleromyography with or without a preload (Hand Adapter; Organon, Oss, the Netherlands). On the contralateral arm, mechanomyography was used. Anesthesia was induced with propofol and an opioid, and neuromuscular block with 0.6 mg/kg rocuronium. The precision and the bias and limits of agreement (with or without normalization) between the methods were evaluated using TOF stimulation., Results: Preload improved the precision of acceleromyography by 21%, but it also increased the mean control TOF ratio from 1.07 to 1.13. Normalization of the acceleromyographic TOF ratios diminished the bias to mechanomyography during recovery (e.g., from 0.15 to 0.05 at TOF 0.90); when the mechanomyographic TOF values were normalized as well, the bias was eliminated. However, normalization did not exclude wide individual differences between acceleromyography and mechanomyography (+/- 0.10-0.20 at TOF 0.90)., Conclusion: Preload increases the precision of acceleromyography, and normalization of the TOF ratios decreases bias in relation to mechanomyography. When both acceleromyography and mechanomyography are normalized, there is no significant bias between the two methods.

Background and Purpose: Recent work demonstrated that application of peripheral nerve and cortical stimulation independently can induce modest improvements in motor performance in patients with stroke. The purpose of this study was to test the hypothesis that combining peripheral nerve stimulation (PNS) to the paretic hand with anodal direct current stimulation (tDCS) to the ipsilesional primary motor cortex (M1) would facilitate beneficial effects of motor training more than each intervention alone or sham (tDCS(Sham) and PNS(Sham))., Methods: Nine chronic stroke patients completed a blinded crossover designed study. In separate sessions, we investigated the effects of single applications of PNS+tDCS, PNS+tDCS(Sham), tDCS+PNS(Sham), and PNS(Sham)+tDCS(Sham) before motor training on the ability to perform finger motor sequences with the paretic hand., Results: PNS+tDCS resulted in a 41.3% improvement in the number of correct key presses relative to PNS(Sham)+tDCS(Sham), 15.4% relative to PNS+tDCS(Sham), and 22.7% relative to tDCS+PNS(Sham). These performance differences were maintained 1 and 6 days after the end of the training., Conclusions: These results indicate that combining PNS with tDCS can facilitate the beneficial effects of training on motor performance beyond levels reached with each intervention alone, a finding of relevance for the neurorehabilitation of motor impairments after stroke.

Objective: To determine normal values for the amplitude ratio of sensory nerve action potential (SNAP) from an ulnar sensory segmental nerve conduction study, and to the evaluate usefulness in the diagnosis of mild-degree ulnar neuropathy at the elbow (UNE)., Design: Segmental sensory conduction study of the ulnar nerve was performed in 71 healthy subjects. Peak latency and baseline to peak amplitudes were measured. The amplitude ratio of below-elbow to wrist (BE/W) stimulations and above-elbow (AE) to below-elbow stimulations (BE) were calculated. Normal cutoff values were obtained by subtracting 2 SD from the mean value, and these values were applied to 22 symptomatic UNE cases. The amplitude ratio was also obtained in six subjects with C8 radiculopathy., Results: The amplitude ratios of BE/W and AE/BE were 0.61 +/- 0.08 and 0.82 +/- 0.08, respectively. The cutoff value of BE/W was 0.45, and that of AE/BE was 0.65. The amplitude ratio of BE/W showed a weak correlation to the length of the forearm segment (r = -0.25, P < 0.05). Five of the 22 UNE patients revealed only reduced amplitude ratios of SNAP across the lesion, whereas all the patients with C8 radiculopathy showed normal amplitude ratios of ulnar SNAP., Conclusions: The amplitude ratio of ulnar SNAPs may be useful in the diagnosis of mild ulnar neuropathy with only sensory symptoms and normal segmental motor conduction.

Objective: To compare results obtained with the NC-stat--an automated nerve testing device--to traditional nerve conduction studies relevant to carpal tunnel syndrome screening., Methods: Thirty-three subjects recruited from patients referred for electrodiagnostic testing were studied. Measurements including the distal motor latency (DML), distal sensory latency (DSL), and median-ulnar latency difference (MUD) were obtained by the NC-stat and by standard nerve conduction studies., Results: With modifications to the NC-stat's suggested reference ranges, sensitivity with respect to the traditional results ranged from 93.8% (sensory MUD) to 100% (median DML and DSL) and specificity ranged from 84.6% (motor MUD) to 94.1% (sensory MUD). Sensitivity was as high or higher and specificity was lower when using the manufacturer's suggested cutoffs., Conclusion: The NC-stat appears to be a convenient and sensitive method for detecting median nerve pathology at the wrist.

Background: In this prospective study we compared the success of the infraclavicular brachial plexus block using double-stimulation in regard to the second nerve response elicited with neurostimulation., Methods: Six-hundred-twenty-eight patients undergoing emergency upper limb surgery using infraclavicular brachial plexus block were included in this study. The musculocutaneous nerve was initially blocked and the groups were then evaluated according to the second nerve located, which was radial in 54%, median in 35%, and ulnar in 11% of patients. Blocks were performed using lidocaine 1.5% with 1/400,000 epinephrine 40 mL in all cases. The block was assessed every 5 min for 30 min after completion of the block., Results: The success rate was 96% for the radial response group, 89% for the median response group, and 90% for the ulnar response group (P < 0.05). Time to perform the block and the onset time were not significantly different among groups. No serious complications were observed., Conclusion: We conclude that having initially located and blocked the musculocutaneous nerve, subsequent injection on a radial response resulted in a slightly more reliable success rate than injection with an ulnar or median response.

Background: To avoid long scar formation after contralateral C7 transfer for treatment of brachial plexus avulsion injuries, endoscopy was used for full-length harvest of the ulnar nerve. The surgical procedure and its clinical effect are reported here., Methods: From July to August of 2001, two patients with total root avulsion were recruited. Three 2- to 3-cm-long incisions were made in the mid upper arm, elbow, and wrist, and the full-length ulnar nerve was harvested using the Endoscope Vessel Harvest System endoscope system. The surgical time was recorded, the vascularity of the dissected ulnar nerves was observed, and the recovery of the injured limb after contralateral C7 nerve root transfer was measured., Results: Compared with the traditional technique, there were no significant differences in surgical time, vascularity of the dissected ulnar nerve, or recovery of the injured limb when the full-length ulnar nerve was harvested with endoscopy (as part of the contralateral C7 nerve root transfer operation), but the degree of scarring after surgery was markedly reduced., Conclusions: Although the same level of curative effect was ensured, the new endoscope-aided method for harvesting the full length of the ulnar nerve for contralateral C7 nerve root transfer was not complicated and caused markedly less scarring.

Background: In patients with Duchenne muscular dystrophy (DMD) the response to nondepolarizing muscle relaxants is scarcely documented and conflicting. The current study was conducted to determine the time to peak effect and the time for complete spontaneous recovery after a single dose of 0.6 mg/kg of rocuronium in patients with DMD., Methods: Twenty-four patients (12 with DMD, 12 controls, aged 10-16 yr) were studied. All patients were anesthetized with propofol and fentanyl/remifentanil. Neuromuscular transmission was monitored by acceleromyography. After induction all patients received a single dose of 0.6 mg/kg of rocuronium. The complete time course of onset and spontaneous recovery were recorded, Results: Significant (P < 0.01) increase in the onset times to 95% neuromuscular block was observed in DMD patients (median, 203 s; range, 90-420 s) compared with controls (median, 90 s; range, 60-195 s). The time between rocuronium administration and recovery of first twitch of the train-of-four to 90% was significantly (P < 0.01) prolonged in DMD compared with controls (median, 132 min; range, 61-209 min versus 39 min; 22-55 min). The recovery index was also significantly prolonged in the DMD group compared with controls (median, 28 min, range, 15-70 min versus 8 min; 3-14 min)., Conclusions: The most striking and surprising result of this study is the delayed onset of blockade in DMD after a standard dose of rocuronium. This effect should be kept in mind in situations when a rapid airway protection is necessary in DMD patients. The documented very long recovery from rocuronium-induced block emphasizes the need for careful assessment of neuromuscular function in DMD patients.

Background: The antidepressant amitriptyline is used as an adjuvant in the treatment of chronic pain conditions. Among its many actions, this drug also blocks ion channels, such as Na channels. Preliminary animal studies suggested that amitripty-line would be a longer-lasting local anesthetic than bupivacaine, with potentially fewer side effects. Therefore, the authors investigated the adverse effects and effectiveness of this drug when given for ulnar nerve blockade in human volunteers., Methods: After obtaining written institutional review board approval and informed consent, a typical phase Ia trial was conducted by administration to the ulnar nerve at the level of the wrist in an open-label, dose-escalating fashion. Amitripty-line hydrochloride, 4 ml, at concentrations of 5, 10, and 20 mM (n = 4-9/group) was used for each volunteer. If no major side effects and nerve block were encountered, comparison in a randomized, double-blinded trial of amitriptyline (20 mM) to placebo and bupivacaine (4 mM) (n = 4-9/group), was to follow. A blunt needle was used to grade the pain, and motor blockade was assessed by the Froment test., Results: There was no significant statistical difference in terms of side effects (pain, swelling, erythema, and sedation) among any groups. The analgesic effects of 20 mM amitriptyline and 4 mm bupivacaine solution were significantly higher than those of the placebo solution., Conclusions: Because of the lack of evidence that amitripty-line provides better nerve blockade than current local anesthetics and the potential for neurotoxicity, its use for peripheral nerve blockade in humans seems limited.

Unlabelled: Postoperative awake patients may have significant residual neuromuscular block. In awake patients, the results of accelerometry are affected by extra movements to which the thumb may be subject. In this study, we evaluated the repeatability of train-of-four (TOF) ratio using acceleromyography in 253 patients recovering from anesthesia. Immediately after arrival in the postanesthesia care unit, the ulnar nerve was stimulated with TOF stimulation. The evoked response at the thumb was measured by the TOF-Watch apparatus. The current intensity was 30 mA. Two TOF stimulations were applied and recorded at 30-s intervals. A Bland-Altman test was used. The Kappa (kappa) test for clinical agreement between the two measurements was also calculated according to the presence or absence of a residual neuromuscular blockade, defined as a TOF ratio <0.9. According to the presence of a residual neuromuscular blockade, the paired TOF ratios were discordant in 61 patients (24%; 95% confidence interval, 21%-27%). The kappa test indicated a moderate agreement (k = 0.47). We demonstrated that accelerometry as used in this study is not always accurate. Two isolated acceleromyograph TOF ratios are not an accurate representation of the neuromuscular status of the patient recovering from anesthesia., Implications: Clinicians should be aware that acceleromyography as used in this study does not always provide precise train-of-four ratio measurements. Two isolated acceleromyograph train-of-four ratios are not an accurate representation of the neuromuscular status of the patient recovering from anesthesia.

Unlabelled: The standard of neuromuscular monitoring is the measurement of the force of contraction (mechanomyography, MMG). Phonomyography (PMG) consists of recording low-frequency sounds created during muscle contraction. In this study, we compared and used both methods to determine neuromuscular blockade (NMB) at the adductor pollicis muscle. In 14 patients, PMG was recorded via a small condenser microphone taped to the thenar mass, and a standard mechanomyographic device was applied to the same arm. In another group of 14 patients, only PMG was measured. After induction of anesthesia, the ulnar nerve was stimulated supramaximally using single twitch stimulation (0.1 Hz) for onset and train-of-four (TOF) stimulation every 12 s during offset of NMB produced by mivacurium 0.1 mg/kg. Onset and recovery indices measured by the 2 methods were compared using Student's t-test (P < 0.05). Similar comparisons were made between the two PMG groups (with or without special board). Agreement between PMG and MMG was examined using a Bland-Altman test. Onset was 165 (68) s versus 172 (67) s [mean (SD)], and maximum blockade was 89 (10)% versus 90 (11)%, for PMG and MMG respectively (NS). Time to 25%, 75%, and 90% recovery was 16.5 (4.2) min, 22.1 (6.9) min, and 24.5 (8.2) min, respectively for PMG, not different from 16.7 (4) min, 22.8 (8.1) min, and 24.8 (8.8) min for MMG. Mean bias was 0% with limits of agreement of -10 and + 10% of twitch height for all signals (MMG minus PMG). Time to TOF of 0.5, 0.7, 0.8, and 0.9, was 1 min faster with PMG than with MMG, with limits of agreement of -1.5 to 3.5 min. Pharmacodynamic data derived without or with special arm fixation were not significantly different. MMG and PMG can be used interchangeably to determine NMB at the adductor pollicis muscle. PMG is easier to apply, does not need a special monitoring board and could be a reliable monitor to determine NMB in daily routine., Implications: Mechanomyography and phonomyography (PMG), a novel method of monitoring neuromuscular blockade (NMB) by recording low-frequency sounds emitted by muscle contraction, can be used interchangeably to determine NMB at the adductor pollicis muscle. PMG is easier to apply, does not need a special monitoring board and could be a reliable monitor to determine NMB in daily routine.

Background: The authors reappraised the conventional wisdom that the intubating dose of succinylcholine must be 1.0 mg/kg and attempted to define the lower range of succinylcholine doses that provide acceptable intubation conditions in 95% of patients within 60 s., Methods: This prospective, randomized, double-blind study involved 200 patients. Anesthesia was induced with 2 mug/kg fentanyl and 2 mg/kg propofol. After loss of consciousness, patients were randomly allocated to receive 0.3, 0.5, or 1.0 mg/kg succinylcholine or saline (control group). Tracheal intubation was performed 60 s later. A blinded investigator performed all laryngoscopies and also graded intubating conditions., Results: Intubating conditions were acceptable (excellent plus good grade combined) in 30%, 92%, 94%, and 98% of patients after 0.0, 0.3, 0.5, and 1.0 mg/kg succinylcholine, respectively. The incidence of acceptable intubating conditions was significantly greater (P < 0.05) in patients receiving succinylcholine compared with those in the control group but was not different among the different succinylcholine dose groups. The calculated doses of succinylcholine (and their 95% confidence intervals) that were required to achieve acceptable intubating conditions in 90% and 95% of patients at 60 s were 0.24 (0.19-0.31) mg/kg and 0.56 (0.43-0.73) mg/kg, respectively., Conclusions: The use of 1.0 mg/kg of succinylcholine may be excessive if the goal is to achieve acceptable intubating conditions within 60 s. Comparable intubating conditions were achieved after 0.3, 0.5, or 1.0 mg/kg succinylcholine. In a rapid-sequence induction, 95% of patients with normal airway anatomy anesthetized with 2 mug/kg fentanyl and 2 mg/kg propofol should have acceptable intubating conditions at 60 s after 0.56 mg/kg succinylcholine. Reducing the dose of succinylcholine should allow a more rapid return of spontaneous respiration and airway reflexes.

Background: The usually cited "intubation dose" of succinylcholine is 1.0 mg/kg. In the majority of patients, this dose will produce apnea of sufficient duration that significant hemoglobin desaturation may occur before neuromuscular recovery takes place in those whose ventilation is not assisted. This study was undertaken to examine the extent to which reducing this dose would decrease the duration of action of succinylcholine., Methods: During stable desflurane/oxygen/opioid anesthesia and after adequate twitch stabilization, neuromuscular function was recorded with an acceleromyographic monitor. Supramaximal stimuli were delivered at 0.10 Hz. Patients received 0.40, 0.60, or 1.0 mg/kg succinylcholine, and twitch height was monitored for at least 20 min thereafter., Results: The onset times to maximal effect were 105 +/- 23 s, 81 +/- 19 s, and 71 +/- 22 s, respectively. The lowest dose (0.40 mg/kg) did not reliably produce 100% twitch depression. The times to 90% twitch recovery at the adductor pollicis in the three groups were 6.6 +/- 1.5 min, 7.6 +/- 1.6 min, and 9.3 +/- 1.2 min, respectively., Conclusions: Reducing the dose of succinylcholine from 1.0 mg/kg to 0.60 mg/kg shortens the duration of effect at the adductor pollicis by more than 90 s. The authors believe that even this modest decrease in the duration of drug-induced paralysis is often worth pursuing.

Unlabelled: Ulnar nerve injury, the most common form of perioperative peripheral nerve injury, has a 3:1 male/female predominance. Neither the mechanism of perioperative ulnar nerve injury nor the reasons for the increased male susceptibility are well understood. We used an experimental model with arm flexion at the elbow, direct pressure on the ulnar nerve, and arm ischemia as distinct stress mechanisms to induce adverse changes in ulnar current perception thresholds (CPTs) on 3 groups of 40 male and 40 female volunteers (a total of 240 volunteers). CPT measurements were repeated at 2000-, 250-, and 5-Hz stimulating frequencies, specific to A-beta, A-delta, and unmyelinated C-fibers, respectively. Ischemia produced significant increases in CPT with all three stimulating frequencies, and there were no detectable differences between men and women. Flexion failed to produce significant CPT increases at any of the three stimulating frequencies, with no sex-based differences. Direct pressure produced significant CPT increases at 5 and 250 Hz, indicating inhibition of both unmyelinated C-fibers and myelinated A-delta fibers. C-fibers, but not A-delta fibers, demonstrated sex differences with direct pressure; there was a 1.7-fold (95% confidence interval, 1.2- to 2.4-fold) greater effect in men. Ischemia significantly inhibited the function of all three fiber types, perhaps sufficient to overwhelm gender differences., Implications: The ability of direct pressure to produce a greater inhibition of unmyelinated C-fibers in male subjects compared with female subjects is consistent with, and may help explain, the male increased susceptibility to perioperative ulnar nerve dysfunction.

Study Design: A retrospective and prospective study was conducted to investigate intraoperative neurophysiologic monitoring during cervical laminectomy to detect iatrogenic C5 nerve root palsy., Objective: To evaluate the usefulness of various intraoperative neuromonitoring methods for identifying C5 nerve root palsy., Summary of Background Data: One unsolved complication after laminectomy or laminoplasty for cervical compression myelopathy is C5 nerve root palsy. It can go undetected even in the presence of intraoperative neuromonitoring with conventional upper extremity mixed nerve or dermatomal somatosensory-evoked potentials or transcranial motor-evoked potentials, recording typically from hand muscles., Methods: The intraoperative neuromonitoring data of 200 patients who underwent cervical laminectomy for myelopathy between 1998 and 2000 were reviewed for C5 nerve root palsy. Retrospective studies were conducted for the first 132 patients, who were monitored with conventional techniques including ulnar and posterior tibial nerve somatosensory-evoked potentials, C5-C7 dermatomally evoked potentials, and transcranial electrical motor-evoked potentials recorded from hand and leg muscles. Prospective studies then were applied to the remaining 68 patients, for whom transcranial electrical motor-evoked potentials and spontaneous electromyography were monitored from deltoid and biceps muscles in the wake of undetected C5 nerve root palsy from conventional neurophysiologic monitoring methods., Results: In the retrospective cohort, six patients presented after surgery with C5 nerve root palsy showing unilateral deltoid muscle paralysis despite entirely unremarkable conventional somatosensory-evoked potentials, dermatomally evoked potentials, and transcranial electrical motor-evoked potentials from hand and leg muscles. For the prospective cohort, two patients experienced postoperative iatrogenic C5 motor nerve root palsy. Impending C5 nerve root injuries after laminectomy were successfully identified in both patients showing significant changes in deltoid and biceps transcranial electrical motor-evoked potentials and spontaneous electromyography, thereby averting more serious consequence. There were no false-negative and false-positive results., Conclusions: In an effort to reduce postoperative C5 nerve root palsy, the clinician should consider intraoperative deltoid and biceps transcranial electrical motor-evoked potential and spontaneous electromyography monitoring whenever there is potential for iatrogenic C5 nerve root injury.

Manipulation of afferent input induces changes in the excitability and organisation of human corticomotor representations. These changes are generally short lived, although can be prolonged by repetition. Here, we charted the time-course of the change of motor cortex excitability induced by electrical stimulation of radial and ulnar nerves. Corticomotor excitability was evaluated by measuring the amplitude of the motor evoked potentials in the first dorsal interosseous muscle by transcranial magnetic stimulation of the optimal cortical area. Measurements were carried out before the start of peripheral nerve stimulation, and then during the peripheral nerve stimulation at 15 min intervals over a period of 2 h. The amplitudes of the motor evoked potentials significantly increased during the 2 h period of peripheral nerve stimulation. Cortical excitability peaked after about 45-60 min stimulation. These clear-cut changes in cortical excitability following peripheral nerve stimulation may reveal some of the mechanisms underlying motor learning and cortical plasticity.

Objective: To compare the sensitivities of motor wrist-to-palm (W-P) conduction velocity and two median-ulnar motor latency differences with that of sensory W-P conduction velocity in the diagnosis of carpal tunnel syndrome (CTS)., Methods: This study included 116 consecutive patients with CTS (160 hands) referred for evaluation and 100 volunteers who served as controls. Median motor and sensory nerve responses with wrist and palm stimulation allowed for the determination of motor and sensory W-P CV (W-P MCV and SCV). Two motor distal latency (MDL) differences between the median-thenar and ulnar-hypothenar (M-U) muscles and between the median-second lumbrical and ulnar-interossei muscles (2L-INT) were measured and calculated. The mean values of controls plus or minus 2.5 SD served as the normal limits., Results: Among the 160 hands with suspected CTS, 11 (6.88%) had normal electrodiagnostic studies and 149 (93.1%) had at least one abnormal electrodiagnostic study. Among the 149 hands with an abnormality, 139 (86.88%) had abnormal W-P MCV and 129 (80.63%) had abnormal W-P SCV. The sensitivity for 2L-INT was 77.5%, and it was 70% for M-U, 68.75% for median MDL, and 73.75% for sensory distal latency. Combining W-P MCV and W-P SCV allowed for the detection of abnormalities in 147 hands (91.88%) and yielded a markedly improved diagnostic rate compared with W-P SCV alone., Conclusion: Motor W-P conduction study is more valuable and no more difficult than sensory W-P conduction study for the diagnosis of CTS. In patients with suspected CTS in whom the results of conventional nerve conduction studies are normal, studying both motor and sensory W-P conduction increases the diagnostic yield.

Previous studies have shown a modification of parkinsonian tremor (PT) by proprioceptive input induced by passive joint movements. The authors investigated the impact of electrically evoked proprioceptive input on PT. In eight patients with PT they recorded surface EMG from the opponens pollicis muscle, and forearm extensors and flexors. Rhythmic electrical stimulation was applied to the ipsilateral median nerve at the wrist using a submaximal stimulus intensity and stimulus frequencies between two stimuli per second and five stimuli per second. The tremor frequency did not adapt to the stimulus frequency. Tremor frequency of parkinsonian resting tremor increased significantly in the directly stimulated opponens pollicis muscle (mean +/- standard deviation, 4.35 +/- 0.64 Hz without stimulation versus 4.53 +/- 0.68 Hz with stimulation; P < 0.05, paired t-test), the not directly stimulated forearm muscles (4.90 +/- 0.72 Hz versus 5.18 +/- 0.73 Hz, P < 0.001), and the upper arm muscles (5.13 +/- 0.61 Hz versus 5.36 +/- 0.68 Hz, P < 0.01). Furthermore, the parkinsonian postural tremor accelerated significantly during ipsilateral median nerve stimulation (5.31 +/- 0.99 Hz versus 5.44 +/- 1.03 Hz, P < 0.05). Parkinsonian resting tremor in the forearm muscles also accelerated significantly during ipsilateral ulnar nerve stimulation (4.85 +/- 0.57 Hz versus 5.05 +/- 0.65 Hz, P < 0.05). Contralateral median nerve stimulation had no significant effect. These results suggest a close interaction between proprioceptive input and PT generation.

Objective: Studies in the literature have demonstrated a gender effect on sensory nerve action potential (SNAP) amplitude for the median and ulnar nerves by use of the antidromic method of recording. The objective of this study was to determine if performing orthodromic sensory nerve stimulation eliminates the gender bias by removing the finger circumference as a variable., Methods: Fifty-five healthy subjects participated in the study. The mean age of the subjects was 37.8 +/- 5.9 yr and 35.3 +/- 5.9 yr for men and women, respectively. Orthodromic sensory nerve conduction studies were performed for the median and ulnar nerves measuring the SNAP amplitude by use of standard electrophysiologic technique., Results: The mean finger circumference of the third digit was 6.5 +/- 0.58 cm for men and 5.9 +/- 0.47 cm for women, and for the fifth digit, it was 5.6 +/- 0.41 cm for men and 5.3 +/- 0.37 cm for women. The median SNAP amplitude and their percentiles of 2.5 and 97.5 for the median nerve were 30.0 microV for men and 28.0 microV for women. For the ulnar nerve, they were 16.5 microV for men and 16.0 microV for women., Conclusion: The study confirmed that orthodromic sensory nerve stimulation did not have any significant effect on SNAP amplitude between men and women.

Ulnar nerve conduction velocity (CV) calculated across the elbow has been shown to be significantly influenced by the position of the elbow. This study investigated the effect of wrist position on ulnar nerve CV in 19 control subjects. Ulnar nerve CV was determined with the elbow flexed at 90 degrees at two different wrist positions. The below-elbow-to-wrist CV was not significantly different between the wrist extended and the wrist flexed. Similarly, the mean across-elbow CV with wrist extended was not significantly different from the CV with the wrist flexed. The authors conclude that wrist position does not affect the calculated ulnar nerve CV across the elbow.

Unlabelled: To evaluate the efficacy and safety of the multiple peripheral nerve block technique at the humeral canal (humeral block) with the use of a neurostimulator, we prospectively studied 1417 patients undergoing upper limb surgery with a brachial plexus block at the humeral canal (1468 blocks). The success rate (defined as sensory block [in all nerve distributions] and/or the absence of another anesthetic technique required to allow surgery) was 95%. The threshold of minimal stimulation used to locate each nerve before injecting the anesthetic solution was the unique predictive factor for identified failure. For the median nerve, the threshold was 0.8 mA with a relative risk of failure (RRf: relative risk evaluated by series of Taylor with a 95% confidence interval) = 1.49 (P = 0.04), for the radial nerve the threshold was 0.6 mA (RRf 1.3, P = 0.02), and 0.7 mA for the ulnar nerve (RRf 1.36, P = 0.04). For any equal or higher stimulation level, the risk of failure of the humeral block increased. For the musculocutaneous nerve, we did not observe a significant stimulation threshold for the risk of failure; although beyond 0.7 mA, the RRf was always more than 1.3. Adverse events occurred in 7% of all cases and were usually minor (nausea/vomiting, anxiety, local pain). Our study provides supplementary information on the efficacy and safety of this technique. Stimulation thresholds are clinically identified for the first time as the main factor linked to the failure of a technique using a neurostimulator. We conclude that the humeral block is a reliable peripheral block allowing good success rates results with minor complications, which can be used as an alternative to the axillary block., Implications: We prospectively evaluated the feasibility and the factors causing failure of a peripheral nerve block technique (humeral block) using neurostimulation in a large number of patients. The importance of the level of stimulation for the success of the block was evaluated for the first time.

Background: A rigorous study of the dose-response relation of rapacuronium has, to our knowledge, yet to be performed. In addition, there is little information available regarding the onset or offset profile of rapacuronium when administered in subparalyzing doses. These issues necessitate further study., Methods: Forty-seven adult patients, American Society Anesthesiologists physical status I or II, were studied. Tracheal intubation was accomplished without muscle relaxants. Anesthesia was maintained with use of nitrous oxide, propofol, and alfentanil. The electromyogram of the first dorsal interosseous muscle was measured using a monitor. Single stimuli at 0.10 Hz were administered. A single dose of rapacuronium was administered. After log-dose or logit transformation of the data, the best-fit line of regression was determined using the method of least squares. For each subject, the authors estimated the 50% effective dose (ED50) and 95% effective dose (ED95) from the Hill equation using the slope obtained from regression analysis. The onset times to 50 and 90% of peak effect were estimated in a subset of 10 individuals in which peak twitch depression decreased to the range of 90-99%., Results: The calculated ED50 and ED95 values for rapacuronium were 0.39 +/- 0.08 (SD) and 0.75 +/- 0.16 mg/kg, respectively. After a single ED95 dose, 90% of the drug's peak effect was evident in 77 +/- 17 s. After this dose, rapacuronium has a clinical duration of 6.1 +/- 1.1 min., Conclusions: The authors found the ED95 of rapacuronium to be substantially less than suggested by previous estimates. Rapacuronium has an onset profile that is not different from that previously reported for succinylcholine. The rate of spontaneous recovery was faster after rapacuronium than the authors previously observed after mivacurium administration but was slower than after succinylcholine, using an identical protocol.

Paralysis after use of a tourniquet during surgery is a well recognized complication. Based on the electrophysiologic findings, 35 cases referred to our electromyography laboratory have been diagnosed as tourniquet paralysis within a 3-yr period. This preliminary report suggests that tourniquet paralysis should be considered during clinical and electrophysiologic evaluations after primary nerve repairs.

In animals simple passive co-activation causes a fusion and expansion of the involved cortical representations. We used passive tactile finger co-activation for 40 min to investigate cortical representational changes in the human somatosensory cortex. Magnetic source imaging revealed that the euclidean distance between median and ulnar nerve somatosensory evoked fields (SEF) was significantly reduced after application of 600 synchronous airpuff stimuli to the fingertips of four fingers. In the control experiment without co-activation no significant change in distance was observed. Perception threshold and spatial two-point discrimination were not affected by the synchronous stimulation. This is in contrast to blind three-finger Braille readers who frequently mislocalize stimuli applied to the reading fingers. This points to a lack of behavioural relevance or the short duration of co-activation.

Background: Previous studies demonstrated that both edrophonium and neostigmine affect mivacurium's pharmacokinetics, thereby potentially affecting its recovery profile. However, those studies were not clinically relevant because mivacurium was still infused after the antagonists were given. In the present study, the authors gave antagonists (or placebo) after discontinuing a mivacurium infusion, thereby obtaining data that are more clinically relevant., Methods: In 18 patients, mivacurium was infused at 10 microg kg(-1) x min(-1) for 40 min, the infusion was discontinued for 15 min and then restarted at the same rate for another 40 min. Patients were randomized to receive 500 microg/kg edrophonium, 50 microg/kg neostigmine, or saline at discontinuation of the second infusion; all subjects received 1 mg atropine. Plasma was sampled during the final 10 min of each infusion to determine steady state mivacurium concentrations and for 15 min after each infusion. Twitch tension was recorded. Mivacurium concentrations after each of the two infusions were compared., Results: After discontinuation of the second infusion, mivacurium concentrations were larger than those after the first infusion at 2 min with edrophonium and at 2, 4, and 7 min with neostigmine. With both neostigmine and edrophonium, twitch tension recovered after infusion #2 more rapidly than after infusion #1; however, the magnitude of this effect was small, Conclusion: Edrophonium transiently slows the rate at which mivacurium concentrations decrease; this is consistent with our previous findings. Neostigmine has a similar, although longer, effect. Despite altering mivacurium's elimination characteristics, both drugs facilitate neuromuscular recovery, although their benefit is small.