Search

Purpose: Diabetic polyneuropathy (PNP) is an important risk factor for foot ulcers. Diabetic dermopathy is more frequent in patients with diabetic neuropathy. We compared clinical and electrophysiological characteristics of PNP localizations/recurrences of foot ulcers, and diabetic dermopathy (DD) between sexes., Methods: Eighty-eight diabetic patients (44 men, 44 women) had an evaluation regarding detailed history of their diseases, lesion-related data, and clinical examination. Nerve conduction velocities (NCV), compound motor action potentials (CMAP), distal latencies (DL), and sensory nerve action potentials were assessed from the right and left peroneal, right median/ulnar nerves., Results: The presence of DD was more common in men (p < 0.001). The mean NCV of ulnar nerves was slower (p < 0.001); mean CMAP values were lower (p = 0.006); and mean DL was longer in men with compared to women (p = 0.003). Although EMG features of peroneal nerves showed no significant difference, diabetic men had more common and severe peroneal nerve involvement (p = 0.004). Carpal tunnel syndrome was more common in women, though not significant. Patients with right-sided ulcers had lower CMAP amplitudes on the right peroneal nerves in regard to left peroneal nerves (p = 0.009)., Conclusions: Our findings suggest that ulnar nerves are more commonly involved in men, with lower CMAP slower NCV values, and longer DL values.

Purpose: When recording with a palm electrode, a premotor potential (PMP) precedes the compound muscle action potential evoked from the second lumbrical muscle following median nerve stimulation. The origin of the premotor potential has remained uncertain. The aim of this study was to determine whether the PMP-2L is a SNAP derived from antidromically activated digital sensory branches of the median nerve., Methods: We recorded three active electrodes were placed over the second lumbrical muscle, the third lumbrical muscle, the fourth lumbrical muscle by multi-channel recordings., Results: PMPs are recorded only over the median digital sensory branches after stimulating the median nerve, while they are recorded only over the ulnar branch after stimulating the ulnar nerve., Conclusions: We conclude that the origin of the PMP is a SNAP arising from antidromically activated digital sensory branches.

Objectives: The goal of this study is to determine the changes in motor and sensory nerve conduction velocity (NCV) of ulnar nerve at elbow area in different angles of elbow flexion and also to define the optimum angle at which there is an ideal correlation between the across elbow and below elbow NCVs of ulnar nerve., Methods: Motor and sensory NCVs of ulnar nerve were studied in 50 able-bodied subjects (100 limbs) for the below elbow and across elbow segments to evaluate the effect of 5 different angles of elbow (0 degrees, 45 degrees, 90 degrees, 110 degrees 135 degrees of elbow flexion) on NCV changes of ulnar nerve. At each angle the across elbow NCVs were measured and compared with below elbow segments., Results: At 0 degrees of elbow flexion the across elbow NCVs were found to be slower than below elbow segments and at 45 degrees there was no statistical difference between below elbow and across elbow NCV. At each subsequent angles of elbow flexion there was an increment in motor and sensory NCVs for the across elbow compared to below elbow segment (P < 0.05). This increment progressed as the degree of flexion increased, so the most erroneous increment was found at 135 degrees of elbow flexion., Conclusions: Since the 45 degrees of elbow flexion was found to be the position of least variation in motor and sensory NCVs between the across elbow and below elbow segments, this position of elbow flexion seems to be the ideal angle during nerve conduction study of ulnar nerve at elbow area. In this position the upper limit of normal difference between across elbow and below elbow motor NCVs (mean + 2SD) was calculated 8 m/sec.

The purpose of this study was to evaluate the relationship between the nerve conduction characteristics in the median, ulnar and radial nerves and presenting skin temperature in non-impaired individuals as they were subjected to electrophysiological testing. Previous researchers artificially manipulated the skin temperature and demonstrated that there was a positive relationship between temperature and nerve conduction velocity and a negative correlation between distal latency and evoked motor action potential (EMAP). The sample population was 50 non-impaired individuals derived from a venue in the New York City and Long Island region. The independent variable was skin temperature. The dependent variables were: motor nerve conduction velocity, motor distal latency, EMAP of median and ulnar nerves, sensory distal latency and sensory nerve action potential (SNAP) of median, ulnar and radial nerves. The data were analyzed using descriptive statistics, the Bonferroni correction factor and correlation statistics. The study showed significant correlation in median motor distal latency, ulnar motor distal latency, ulnar sensory distal latency, median sensory amplitude, and ulnar sensory amplitude. The NCV, the distal latency and the amplitude of the median, ulnar and radial nerves were similar in values to other researchers' normal values.

Objective: First, to propose a new technique for measuring muscle fiber conduction velocity (MFCV). Second, to ascertain the validation of the new method that uses F-waves (F-MFCV) in healthy volunteers. Third, to examine the relationship between F-MFCV and motor nerve conduction velocity (MCV) in the same subjects., Subjects and Methods: F-waves reflecting single motor units were recorded with a multi-channel surface electrode array and weak electrical stimulation to the median or ulnar nerves in 21 healthy volunteers. F-MFCVs of the abductor pollicis brevis (APB) and abductor digiti minimi (ADM) were calculated from the F-wave peak latency in each channel. MFCV during minimal voluntary contraction (V-MFVC) was measured in the same muscles., Results: There was no significant difference between F-MFCV and V-MFCV in the muscles tested The mean F-MFCV value was similar to recently reported MFCV values generated by minimal voluntary contraction. No significant differences were found between the APB and ADM F-MFCVs, whereas the MCV of the ulnar nerve was faster than that of the median nerve., Conclusion: The MFCV in a single motor unit could be measured with a multi-channel surface electrode array by recording F-waves induced by weak stimulation. Since V-MFCV generated by minimal voluntary contraction is explained by the size principle, V-MFCV reflects small and slow conducting motor unit. There was no significant difference between F-MFCV and V-MFCV. It seemed that F-MFCV also reflected small motor unit. The reason for the lack of difference in the F-MFCVs of the ADM and APB is considered to be a relatively slow F-MFCV. Moreover, MCV reflected the speed of the fastest nerve fiber, whereas F-MFCV did not.

Background and Purpose: There are two commonly accepted techniques used for distal electro-stimulation placement when performing median motor nerve conduction studies. The purpose of this study was to compare latency using two commonly accepted sites of distal stimulation of the median nerve when performing motor nerve conduction studies on non-impaired adult humans., Participants: The sample consisted of 36 non-impaired participants (15 female, 21 male) aged 20 to 40 years., Methods: Participants were randomly assigned to two groups and tested bilaterally for the median motor nerve. For distal stimulation of the median motor nerve, in the first group, 8 cm was measured from the center of the muscle diagonally to arrive at a point between the flexor carpi radialis and plamaris longus tendons. In the second group, 3.5 cm was measured from the distal wrist crease proximally along the median nerve for the distal stimulation of the median motor nerve. Distal latency of both techniques was obtained. Surface skin temperature of the palm was recorded throughout the procedures., Results: No significant differences were found between the 8 cm and 3.5 cm techniques at p < or = 0. 05 level., Comment: Even though no differences were found between the two techniques, the 3.5-cm technique is recommended because of its consistency as an anatomical landmark reducing the potential for measurement error.

The purpose of this study was to determine a relationship between surface temperature of the limb and neuronal characteristics of the median and ulnar nerves in non-impaired individuals. Previous literature demonstrates that there is a negative correlation between distal latency and amplitude and temperature while a positive correlation exists between nerve conduction velocity and temperature. It is a common clinical practice to externally manipulate the temperature of a cold limb. Thirty-six participants (21 male, 15 female,) with an age range between 20-38 years old (mean age = 26.6) completed the study. Temperature of the limb was not manipulated by the researchers prior to testing and was measured at the distal wrist crease using a surface probe. Relationship was determined using a Pearson product-moment coefficient of correlation. A significant negative correlation existed for median distal sensory latency (DSL), ulnar DSL, ulnar motor amplitude (CMAP), and ulnar sensory amplitude (SNAP). The investigators conclude that temperature is a factor to consider when performing nerve conduction studies. The researchers suggest using mathematical correction factors to compensate for a cool limb rather than external heating.

Supramaximal compound sensory nerve action potentials (CSNAPs) were recorded antidromically from five fingers of the same hand to electrical stimulation of the median, ulnar, and radial nerves in 17 normal subjects. The mean amplitudes of the median CSNAPs from the thumb, index, and middle fingers were similar in values. There was minimal radial sensory contribution to the thumb, with the mean radial CSNAP amplitude about one-fourth the size of the median CSNAPs. The mean median and ulnar CSNAP amplitudes from the ring finger were approximately half, and the mean ulnar CSNAP amplitude from the little finger was approximately 85%, of the median CSNAP amplitudes from the other fingers. The median, ulnar, and radial sensory nerve conduction velocities were close in values. There appears to be less variability in the population normative data when the size of the CSNAPs is expressed in terms of amplitude ratio rather than in absolute amplitude value.

Objective: Carpal Tunnel Syndrome (CTS) is commonly bilateral, but symptoms and EMG/NCS abnormalities may be seen unilaterally. This study was designed to determine whether there are any subclinical nerve conduction abnormalities on the "uninvolved" side., Design: Statistical analysis of electrodiagnostic data., Setting: Outpatient academic electrodiagnostic laboratory., Patients: Twenty-two successive patients referred for bilateral upper extremity NCS/EMG with no symptoms or physical signs of CTS and totally normal results, and ten successive patients with an EMG/NCS diagnosis of CTS on one side, and completely normal EMG/NCS on the contralateral side., Results: The median motor and sensory latencies at the wrist were significantly longer in the contralateral "uninvolved" limb than normals (median motor latency 3.75 vs. 3.30 msecs, p = 0.0005, median sensory latency 3.40 vs 3.00 msecs, p = 0.0002). Median sensory amplitude was smaller in the contralateral limb (30.5 uV vs. 41.5 uV, p = 0.0062). The (median-radial) D1 sensory latency difference was greater in the contralateral wrist (0.2 vs. 0.0 msecs, p = 0.0217). The (median-ulnar) sensory latency difference was not significantly increased (0.15 vs. 0.10 msecs, p = 0.2020)., Conclusions: The contralateral limbs of patients with unilateral CTS show significant differences from normals in 4 out of 5 nerve conduction parameters. There is evidence of frequent subclinical median nerve compression in this group.

The aim of this work was to examine the segmental motoneuron activity as a possible mechanism of tremor generation. Eighty-three patients with different types of tremor (25 with Parkinsonian, 29 with essential, and 30 with enhanced physiological tremor due to anxiety), 25 Parkinsonian patients without tremor and 30 healthy volunteers were examined. The tremor was studied clinically and by electromyography in all limb positions. The F wave was examined for assessment of motoneuron activity. The wave was recorded after stimulation of the ulnar, median, tibial and fibular nerves. The maximal and mean F wave amplitudes, frequency of occurrence and number of phases were increased, and the duration was prolonged in all group of patients as compared to the healthy persons. The maximal and the mean F/M amplitude ratios, as well as the Fmean./Fmax amplitude ratio were increased in all groups of patients. All F wave parameters were most altered in Parkinsonian tremor patients followed by patients with rigidity. In conclusion increased motoneuron activity participates in generation of different types of tremor and in Parkinsonian rigidity.

There is room for considerable error in the measurement of across-elbow conduction velocity due to the different possible positions of the elbow and the difficulty in accurately measuring distance. A standardized method should be used for clinical measurement. Many advocate a fully flexed elbow position with the arm abducted at 90 degrees. When the elbow is fully flexed, skin measurement across the bent elbow is difficult with respect to defining the path, which most accurately follows the nerve. However, studies on measurement technique for across-elbow segment have not been performed to date. We have proposed a standardized technique for the measurement of conduction velocity through the elbow segment. We assumed "ideal" across-elbow segmental conduction velocity is the mean of the forearm and arm segmental conduction velocities, and established an optimal deflection point at the elbow, which best reflects the ideal conduction velocity. The optimal deflection point was located medially two thirds distance between the epicondyle and the olecranon in an arm abducted 90 degrees, fully flexed elbow position. Our data suggests that an across-elbow segment velocity lower than 57.8 m/sec, or a difference of more than 7.7 m/sec between the across-elbow and forearm segments is to be considered abnormal. The lower limit values expressed as mean-2 S.D. for absolute across-elbow segmental conduction velocity and relative velocity difference between the across-elbow segment and forearm segments at other possible deflection points of the elbow were also calculated.

Background and Purpose: The purposes of this study were to explore reliability of the ulnar F-wave minimum latency (Fmin) and the ulnar distal motor latency (DML) and to contrast those levels of reliability in order to reveal whether physiologic lability is the primary contributor to unwanted variability in Fmin measurements., Subjects and Methods: Fmin and DML in the Abductor Digiti Minimi muscle were measured bilaterally by two raters in 50 healthy adults (n = 100 hands, 70 male, 30 female) with 3-14 days between testing sessions., Results: Intrarater reliability (ICC 3,1) for the Fmin was 0.89 with a standard error of the measurement (SEM) of 0.77 msec. Interrater reliability (ICC 2,1) for the Fmin was 0.80 with a SEM of 1.04 msec. Intrarater reliability (ICC 3,1) for the DML was 0.71 with a SEM of 0.18 msec. Interrater reliability (ICC 2,1) for the DML was 0.76 with a SEM of 0.19 msec., Discussion and Conclusions: Contrary to our hypothesis, the Fmin had a higher reliability than the DML. The DML did not display the high reliability other investigators have reported. We conclude the Fmin is a reliable measurement when 10 supramaximal stimulations are administered to healthy, young to middle-aged adult subjects. However, no inferences were made regarding relative levels of psychologic lability for the two latencies.

Introduction: The present study aims at exploring the changes in the functioning of the ulnar nerve in a high power magnetic field., Methods: 12 volunteers with a healthy peripheral nervous system participated in the study. The ulnar nerve was selected from the upper organs as the site for study. The functioning of both the sensory and motor parts of the ulnar nerve in normal conditions was electromyographically tested. Then, using the same setting, the functioning of the nerve was electromyographically tested within a high power magnetic field (0.2 Tesla). With regard to the sensory function, the distal latency and the amplitude were examined. With regard to the motor section, the duration, amplitude of the evoked potentials, and latency from two sites--distal and proximal--were examined. These results of the two readings, taken in normal condition and in a high power magnetic field, as well as the motor neural conduction velocity, were compared., Results: The statistical analyses indicated that the changes in both the distal latency and amplitude of the sensory part of the ulnar nerve were significant. However, the changes in the motor function of the nerve were not significant.

A controversial aspect in F-wave studies is if these potentials are generated preferentially by large motoneuron or by motoneuron of all sizes. The purpose of this work is to compare the maximum and minimum conduction velocities of the fibers that generate the M-wave with the maximum and minimum conduction velocities of the F-waves elicited by ulnar nerve stimulation. There were no significant differences between maximum velocities. However, minimum F-wave velocity was significantly higher than minimum conduction velocity, suggesting that the F-waves registered were preferentially generated by the fastest conducting axons.

Normal values of sensory nerve action potential (SNAP) amplitudes vary widely. There are many factors which can influence the amplitude of the SNAP, such as the type of recording techniques, temperature, distance between recording electrodes, skin impedance, etc. In this study, we investigated the correlation between wrist thickness (palmar to dorsum diameter) and amplitudes of the SNAP of median and ulnar nerves of 20 healthy subjects. Ring electrodes were placed on the second and the fifth fingers and a surface block electrode was placed at the wrist between the flexor carpi radialis and the palmaris longus tendon and just radial to the flexor carpi ulnaris tendon, for testing the median and ulnar nerves, respectively. Both orthodromic and antidromic techniques were used. Depending on the technique, either ring or surface block electrodes could be the stimulating or the recording electrodes. By supramaximal intensity stimulation, the amplitude of the SNAP was measured from peak to peak. The results revealed that SNAP amplitudes and wrist thickness are reversely correlated, with statistical significance (p < or = 0.005) by using the antidromic technique. The influence of wrist thickness on SNAP amplitudes should be recognized when performing an electrodiagnostic study to determine axonal degeneration by using the SNAP amplitude parameter.

Objective: The aim of this study was to explore the value of turns/amplitude analysis system in EMG in evaluating peripheral nerve regeneration., Methods: Twenty-eight patients were investigated using turns/amplitude analysis system and conventional method in EMG after nerve repair. The patients were grouped according to their muscle power and their parameters in EMG were recorded and compared among groups as well as between the two methods., Results: Statistical differences of recovery percentage were shown among the groups except turns between M3:M4 using turns/amplitude system. However, none of the differences were present among them using conventional method. Among the parameters, amplitude/s advanced the fastest although it was the lowest at early stage and it also got the highest correlation coefficient (r = 0.848)., Conclusion: Turns/amplitude system was a reliable and sensitive method for evaluating nerve regeneration during nerve repair, which is more precise than the conventional method, and the amplitude was closely related to muscle function recovery.

Background and Purpose: The purpose of this study was to measure the test-retest reliability of the ulnar F-wave minimum latency (Fmin) in normal adults. A reliable Fmin measure allows clinicians to ascribe changes in latency to true changes in a subject and not merely random daily variation., Subjects and Methods: Fmin in the Abductor Digiti Minimi muscle was measured bilaterally in 49 healthy adults (n = 98) with a three day separation between tests., Results: The Fmin reliability estimate as measured by intraclass correlation coefficient (3,1) was 0.59 with a standard error of measurement (SEM) of 1.3 msec. A paired t-test showed no significant difference (t = 1.7, df = 97, p > 0.05) between the mean scores from the two testing sessions., Discussion and Conclusions: We found moderate reliability and relatively low precision (high SEM) in Fmin scores taken from healthy individuals on two separate days. Strict adherence to our protocol and an acceptable overall precision of measurements (as measured by mean scores) suggest the contributions of rater and instrument error were low in our study. We conclude that 1) valid clinical interpretation of minimum F-wave latency findings is questionable because the Fmin measurement appears to have only moderate reliability, and 2) the lability of the phenomenon itself is the most likely contributor to variability in the Fmin latencies. Further research is warranted before electrophysiologists may be justified in attributing small changes in the Fmin to actual changes in the subject.

To determine the diagnostic efficacy of F-wave amplitude and F/M-ratio measurements in routine electrodiagnostic examinations, normal values were established for the ulnar nerve and systematically applied to a group of patients with various nosological entities (Mononeuropathies at the elbow, radiculopathies of C8, polyneuropathies, anterior horn cell disorders, plexopathies, syringomyelias, others). As a result, F/M-ratio can distinguish between the various pathological conditions (P = 0.02). Patients with radiculopathy and accompanying myelopathy were identified by increased F/M-ratio. It is concluded that F-wave amplitude analysis can give hints for additional central pathology in the individual case.

Background and Purpose: The purpose of this study was to compare the effects of two commonly used stimulating electrode placements on F-wave latency., Subjects: Fifty healthy subjects aged 20 to 47 years were tested., Methods: F-waves were obtained from median and ulnar nerves bilaterally. A total of 200 nerves were tested., Results: A paired t-test indicated a statistically significant difference in F-wave latency between the two stimulating electrode placements. Stepwise linear regression equations demonstrated that our results were consistent with previously published studies., Conclusion and Discussion: Although a statistically significant difference exists between the two techniques, the magnitude of the difference is not likely to be clinically important. Therefore, the most important factor may be to use a consistent technique when investigating potential neuropathies.

This work describes the results of two experimental procedures related to the short latency median nerve somatosensory evoked potentials. In the first one, it was possible to show that there is a different rate of increase in the amplitude of the different components related to different intensities of stimulation. In the second one, the simultaneous stimulation of the median and the ulnar nerves disclosed an occlusive interaction which was larger for the N18 than for the other components. These results may be a support to the hypothesis that the N18 component generator is related to the mechanism of presynaptic inhibition within the cuneiform nucleus.

F wave latency has been shown to be a valuable method in evaluation of a variety of neurologic disorders. We measured F wave values in 50 healthy individuals in Shiraz. Maximum normal F wave latency for median nerve was 25.7 ms for women and 28.5 ms for men with stimulation at the wrist. It was 23 ms for women and 25 ms for men with stimulation at the elbow. Maximum normal F wave latency for ulnar nerve was 26.45 ms for women and 28.9 ms for men with stimulation at the wrist. It was 23.1 ms for women and 25.3 ms for men with stimulation at the elbow. Maximum normal difference in F wave latency between right and left upper extremities with stimulation at the wrist for total group was 2.2 ms for median nerve and 2.4 ms for ulnar nerve. Maximum normal difference in F wave latency between median and ulnar nerve in an extremity with stimulation at the wrist for total group was 2.7 ms. There was statistically significant difference in F wave latency between women and men.

We investigated the effect of age on nerve conduction parameters to establish a diagnostic validity in demyelinating neuropathies of the aged. We evaluated 257 subjects (age 10-76 years old) with no history or signs of peripheral neuropathies. The CMAP amplitude ratio (proximal CMAP/distal CMAP), duration ratio, and area ratio were almost the same throughout the second to eighth decades. The respective lower limits of the normal CMAP amplitude ratio (mean-3 SD) were 0.79 (median nerve), 0.75 (ulnar nerve), 0.57 (peroneal nerve), and 0.45 (tibial nerve). The upper limits of the normal CMAP duration ratio (mean +3 SD) were 1.21 (median nerve), 1.22 (ulnar nerve), 1.37 (peroneal nerve), and 1.35 (tibial nerve). The lower limits of the normal CMAP area ratio (mean-3 SD) were 0.81 (median nerve), 0.78 (ulnar nerve), 0.60 (peroneal nerve), and 0.57 (tibial nerve). No age-related changes were observed in the amplitude ratio or duration ratio SNAP, although the standard deviation increased with age. Since the amplitude, duration and area ratios are easily calculated and age-independent, they can provide useful and reliable information on aged patients with demyelinating neuropathies by conventional nerve conduction studies.

Ulnar, median, and radial proximal nerve action potentials (PNAPs) were recorded from the axilla and supraclavicularly, with stimulation of the nerves at the elbow or the radial groove, in 30 control subjects for each nerve. In addition to routine nerve conduction studies, wrist to elbow median nerve action potentials were recorded proximal to the lesion in 76 patients with carpal tunnel syndrome of varying degrees of severity to determine the effect that the distal lesion might have on more proximal nerve conduction. Utilizing this information, PNAPs, standard nerve conduction studies, and needle electrode examinations were carried out in patients with focal elbow area nerve or brachial plexus lesions producing axonotmesis. PNAPs confirmed the site of the lesions producing axonotmesis when localization was possible with standard nerve conduction and/or needle electrode studies and were the sole means by which localization of the lesions producing only sensory axonotmesis was accomplished.

Fifteen nerves were examined in 10 healthy subjects, using a collision technique with 2 stimulation pulses of different intensity on the same point. The F-waves which occurred after the antidromic activation of the motor neuron cells by the first supramaximal pulse were blocked on their return pathway by the collision with the depolarization induced by the second pulse. The progressive decrement of the voltage of the second stimulus allowed, the transmission of the recurrent discharge along motor fibers with a lower depolarization threshold. The amplitude and the persistence of the F-waves increased (p < 0.05 and p < 0.001 respectively), while their latency decreased (p < 0.01) concurrent with the liberation of additional motor neurons with a lower threshold of depolarization. These findings suggest that the F-wave may be elicited in motoneuron of different depolarization threshold but primarily in larger and faster nerve fibers, with a lower threshold of depolarization.

We studied the sensory action potentials (SAP) of median and ulnar nerves in four groups of 20-30, 30-40, 40-50 and 50-60 years old healthy subjects. In each group ten sensitive ulnar and median nerves were examined stimulating respectively V and III hand digital nerves, with two compared methods. In the former stimulus intensity was 20 mA, with a duration 0.1 msec, and SAP was recorded with averaging technique after 20 stimuli; in the latter the stimulus intensity was supra maximal (100 mA), with a duration 0.1 msec and a single SAP was recorded. The SAP's recording was performed by bipolar surface electrodes at the wrist, following conventional techniques. There was not statistically significant difference between SAP's latencies obtained with the two methods in each group, even if there was a decrease of the latency value obtained with supra maximal stimulus. Otherwise there was a statistically significant increase of SAP's amplitude obtained with supra maximal stimulus, above all in elderly people for median (p < 0.001) and ulnar (p < 0.0005) nerve.

Central conduction times (CCTs) in the motor pathways were assessed in normal subjects using a magnetic stimulus for the recording of cortical and spinal (Cv7 and L4-L5) Motor Evoked Potentials (MEPs) as well as F-waves in upper and lower limbs. M-responses of maximal amplitude could be reliably obtained by using a 4.5 Tesla coil and a stimulus intensity of 85% of the maximal output. It was found that the CCTs derived from the latency difference between cortical and spinal MEPs were, on average, 0.90 ms and 3.15 ms longer, respectively for upper and lower limbs, than those obtained by combining cortical MEPs and F-wave latency measurements. This difference is similar to that reported when electric stimulation is used to elicit F-waves and/or spinal MEPs. It suggests that motor root fibers are depolarized at a distance of 7.8 and 17 cm from the cord by a spinal magnetic stimulus applied respectively at Cv7 and L4-L5 levels. This study shows that magnetic stimulation alone permits to assess CCT in motor pathways with the same reliability as any of the other stimulation modalities hitherto proposed in literature.

A complete ulnar innervation of all thenar muscles, including the opponens, have to our knowledge been described only in patients with severe traumatic lesions of the median nerve. The present study reports a subject with exclusive ulnar innervation of the thenar muscles in the right hand. The patient had no anamnestic or objective signs of peripheral nerve lesions. While his sensory and motor ulnar nerve fibres were normal, electrophysiological examination of the right median nerve showed normal course of the sensory fibres but apparently no motor fibres to the thenar muscles.

In 50 ulnar nerves of healthy subjects, F-wave latency, duration, amplitude and persistence were determined at different frequencies of the antidromic impulse (0.2-0.5-1-2 Hz). The F amplitude and persistence were found significantly increased at higher stimulation rates, suggesting that the frequency of the antidromic impulse influences the motoneuron pool discharges. Individual cross-correlation values (r) obtained for latency and duration, latency and amplitude, amplitude and duration did not show any significant changes at different stimulation rates.

We used the 9 cm Cadwell magnetic coil, stimulating at the wrist, to obtain simultaneous median and ulnar nerve F-responses. Surface recording was performed from conventional thenar and hypothenar sites. It is known that with this type of coil it is difficult to accomplish selective supramaximal stimulation of the median or ulnar nerve individually. We found it possible, however, to record a compound muscle action potential of supramaximal or near supramaximal amplitude, as well as F-responses, in both thenar and hypothenar muscles simultaneously. We assessed this technique for F-response latency determination in controls and patients with carpal tunnel syndrome. In controls, there was no significant difference in the F-minimal latency or the F-minimum-maximum range obtained by the two methods. In patients with carpal tunnel syndrome, with median F-responses very delayed or absent on conventional testing, magnetically elicited thenar F-responses were of shorter latency, similar to F's recorded in the hypothenar muscles, suggesting they were recorded from ulnar innervated thenar muscles. Although magnetic stimulation allows simultaneous determination of median and ulnar F-latencies, sparing patients several painful stimuli, and shortening the electrophysiologic examination, magnetic stimulation in patients with carpal tunnel syndrome may elicit thenar recorded F-responses that are not of median origin. Use of this technique is limited by the lack of focality of the stimulus, which has been the major limiting factor in its use on peripheral nerves.

Various parameters of the F-response (latencies, chronodispersion, amplitude, duration, shape, persistence) were investigated in ulnar and tibial nerves of 50 healthy subjects of both sexes, aged between 16 to 79 years. The observations were made bilaterally and the results revealed no significant differences in any of the F-parameters by comparing side to side. The relationships between each neurophysiological F-response data and limb length, age and sex of control subjects were determined. Correlations of high statistical significance were found between minimum F-latency and limb length as well as between absolute and F%/M-amplitude and age. Cross-correlation coefficients correlating mean individual values of latency-duration, latency-amplitude and amplitude-duration did not show any significant relationship between latency, amplitude and duration in normal subjects.

Electroneurographic and thermographic investigations were done in 32 persons. Sensory nerve conduction velocity, amplitude of sensory nerve potential, subjective and objective sensory thresholds were determined during stimulation of each finger. The maximal and minimal skin temperatures for each finger were evaluated from thermograms taken from the dorsal and palmar surface of the hand before and after standard cooling test. The measurements were done in a thermostabilised room at 19-21 degrees C effective ambient temperature. The second degree correlations between the electroneurographic and thermographic parameters were calculated. The statistical analysis revealed the presence of a double correlation pattern depending on the homoiothermic or poikilothermic thermoregulatory ability of the finger. The differentiation threshold criterion for the poikilo- and homoiothermic group assignment was the minimal rest temperature of the finger equal to 28 degrees C. The correlations in the poikilothermic fingers were very strong and much stronger than in the homoiothermic fingers. Correlations with temperatures were strong both at rest as well as after cooling. Correlations for the sensory nerve potential amplitude likewise for the objective and subjective thresholds were stronger than for the conduction velocity. Sensory nerve potential amplitude increases and subjective and objective thresholds decrease with finger temperature. The obtained results suggest that sensory nerve conduction is related not only to the actual tissue temperature but also to local thermoregulatory ability.

In a study of the relationship between height and the somatosensory evoked potentials (SEPs) in 24 normal individuals, we found significant linear correlations between height and the latencies of major peaks along the pathway in the median, ulnar, and first, third, and fifth digital SEPs. Thus, we conclude that the measured latency should be compared with the expected latency according to the subject's height before it is interpreted as normal or abnormal.

Identification of incomplete motor conduction block (CB) by the usual single stimulation method is problematic when impaired conduction velocity of the axons spared by the block exists at the site of the presumed CB, leading to desynchronisation. Indeed, the area of the compound muscle action potential (MAP) evoked by stimulation applied above this site may be reduced by the phase cancellation related to desynchronisation. A triple stimulation method with double collisions allows virtual displacement of the CB distally to the site where desynchronisation occurs. A first stimulus applied on the nerve above the site of the CB is followed--after a delay--by a stimulation applied distally on the nerve where a collision occurs. This collision, however, does not concern the antidromic wave of the blocked axons which travels towards the block. A third stimulus is then applied--after a second delay--below the site of the CB, where a second collision occurs in the blocked axons. Thus, the third stimulus evokes a MAP that concerns only the unblocked axons, as would the stimulus applied above the site of the CB. In this manner, desynchronisation occurring at the CB site is avoided. The method was developed on simulated CBs of the ulnar nerve at the elbow of 33 normal subjects and compared with the usual single stimulation method. Subsequently, it was evaluated on 8 pathological CBs of the ulnar nerve at the elbow and of the peroneal nerve at the fibular head. The method detects CBs of 5% or more despite the occurrence of desynchronisation.

A computer program is described for the collision technique by which data acquisition and data interpretation is possible. Paired stimuli with varying interstimulus times evoke a muscle action potential. The amplitude or the rectified area integral as a function of interstimulus times was used to define the scatter of conduction velocities within the ulnar nerve. In normal and slightly distorted EMG signals the amplitude and area produces the same scatter. In distorted potentials the integrated area is more sensitive. The technique was furthermore used to separate two different age groups of normal persons. Significant differences were seen as well as in an age matched group of patients with myotonic dystrophy. The collision technique and the computer program proved to be sensitive and applicable in routine examinations.