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Introduction Suprascapular neuropathy (SSN) is rare, with an estimated prevalence of 4.3% in patients with shoulder pain. Methods This retrospective chart review included patients with SSN seen during a 16-year period. Demographics and clinical information were recorded. Descriptive statistics, including percentages, means, and standard deviations, were computed for the variables of interest for all patients. Results Of 87 patients included in this study, trauma (n = 27) was the most common cause of SSN, followed by neuralgic amyotrophy (n = 21). Fifty-seven patients had isolated SSN. Others had SSN associated with axillary neuropathy (23 patients), brachial plexopathy (3 patients), and long thoracic, radial, or spinal accessory neuropathy (1 patient each). Discussion SSN is commonly associated with axillary neuropathy. Trauma remains the most common cause of SSN. Electrodiagnostic findings aid in the initial diagnosis and may indicate the need for close clinical follow-up based on the severity of the axonal injury.

A consecutive series of twenty-seven patients who had thirty acute unstable (type-C) fractures of the pelvic ring was studied prospectively to evaluate the use of stimulus-evoked electromyography to decrease the risk of iatrogenic nerve-root injury during the insertion of iliosacral screws. A prerequisite for inclusion in the study was a normal neurological status preoperatively; somatosensory evoked potentials were monitored to further document the neurological status both before and after insertion of the screw or screws. A total of fifty-one iliosacral screws were inserted, and a current threshold of more than eight milliamperes was selected as the level that indicated that the drill-bit was a safe distance from the nerve root. Four of the fifty-one screws were redirected because of information obtained with stimulus-evoked electromyography. Postoperatively, all patients had a normal neurological status. Computerized tomography, although not accurate for detailed measurements, demonstrated that all of the screws were in a safe, intraosseous position. Monitoring with stimulus-evoked electromyography appears to provide reliable data and may decrease the risk of iatrogenic injury to the nerve roots during operations on the pelvic ring.

Objective: A canine model was designed to evaluate the feasibility of stimulus-evoked electromyographic (EMG) monitoring of the lumbosacral nerve roots during the insertion of iliosacral implants. Study Design/Methods: Four 2.5-millimeter Kirschner wires (K-wires) were percutaneously inserted under general anesthesia into the S1 body of each of five dog hemipelves using C-arm fluoroscopy image-intensifier control in an actual attempt to compromise the S1 canal and the S1 nerve root. A searching current of twenty milliamperes was initially applied to the K-wire with monitoring electrodes placed in the gastrocnemius muscle. Current thresholds required to evoke an EMG response were recorded for each K-wire. Actual K-wire location was determined by anatomical dissection. Results: Evaluation of these twenty wires revealed that current threshold was directly related to the proximity of the K-wire to the nerve root, with a correlation coefficient of 0.94 (p < 0.001). Conclusions: Stimulus-evoked EMG monitbring provided reliable data indicating the proximity of the iliosacral implants to the sacral nerve root. This method of intraoperative nerve monitoring could potentially decrease the risk of iatrogenic nerve root injury during pelvic ring surgery. Further study is warranted.

Cutaneous silent period (CSP) was measured on stimulating digits 2 and 5 in 19 patients with carpal tunnel syndrome (CTS) and compared with 20 healthy volunteers. In 2 patients with severe CTS, CSP was absent on digit 2 but present on digit 5. In mild/moderate CTS digit 2 CSP mean duration was 50.9+/-13.9 ms, significantly longer than control subjects (36.9+/-8.7 ms) (P = 0.005). CSP was found to be abnormal in CTS, being absent in severe and prolonged in mild/moderate cases.

Background: The use of continuous electromyographic and somatosensory-evoked-potential monitoring systems has been advocated to assist in avoiding nerve-root injury during operations on the pelvic ring. More recently, it was suggested that stimulus-evoked electromyographic monitoring may further decrease the risk of iatrogenic nerve-root injury during posterior pelvic fixation by enabling the surgeon to determine the actual distance of an implant from a nerve root. The purpose of the current study was to evaluate the relative efficacy of these three methods of monitoring for minimizing the risk of neural injury during the placement of iliosacral implants. Methods: While the function of the first sacral nerve root was monitored with the use of stimulus-evoked electromyographic, continuous electromyographic, and somatosensory-evoked-potential monitoring techniques, a 2.0-millimeter stainless-steel Kirschner wire was progressively inserted, guided by a high-speed computerized tomographic scanner, into the first sacral body of seventeen hemipelves in nine dogs. The end point was contact with the nerve as demonstrated by the computerized tomographic images. It was expected that this end point would be heralded by a burst of spontaneous electromyographic activity and an abnormal somatosensory-evoked-potential signal. Anatomical dissection at the completion of the study documented the final position of the Kirschner wire. Results: Anatomical dissection demonstrated compression or penetration of the nerve root in sixteen of the seventeen specimens. A spontaneous burst of electromyographic activity was not recorded for any specimen on continuous electromyographic monitoring; this finding was significantly different from what had been expected (p < 0.001). Because of technical problems, somatosensory evoked potentials could be recorded for only twelve hemipelves that had nerve-root compression or penetration, and abnormal somatosensory evoked potentials were recorded for only one of the twelve; this finding was significantly different from what had been expected (p < 0.001). A total of 113 stimulus-evoked electromyographic data points were obtained. The correlation coefficient for the relationship between the current threshold recorded with stimulus-evoked electromyographic monitoring and the distance of the wire from the nerve was 0.801 (p < 0.001). The actual measured current thresholds were of an observed proportion not different from what had been expected (p = 0.48). Conclusions: Continuous electromyographic and somatosensory-evoked-potential monitoring techniques failed to indicate contact with the nerve root reliably in this animal model. However, stimulus-evoked electromyographic monitoring consistently provided reliable information indicating the proximity of the implant to the nerve root. Clinical Relevance: This investigation raises serious concerns regarding the validity of somatosensory-evoked-potential and spontaneous electromyographic monitoring for the purpose of minimizing nerve-root injury during the insertion of iliosacral implants. In addition, it further confirms the validity of the relationship between the stimulus-evoked electromyographic current threshold and the distance between the wire and the nerve and its potential applicability for nerve-monitoring.

Cutaneous silent period (CSP) was measured on stimulating digits 2 and 5 in 19 patients with carpal tunnel syndrome (CTS) and compared with 20 healthy volunteers. In 2 patients with severe CTS, CSP was absent on digit 2 but present on digit 5. In mild/moderate CTS digit 2 CSP mean duration was 50.9+/-13.9 ms, significantly longer than control subjects (36.9+/-8.7 ms) (P = 0.005). CSP was found to be abnormal in CTS, being absent in severe and prolonged in mild/moderate cases.

Objectives: We hypothesized that the hyperexcitability of occipital cortex neurons may predispose migraine subjects to develop spreading depression, the putative basis of migraine with aura (MwA). To date there is no direct physiologic correlate confirming this in patients. Accordingly, we evaluated the differences in the threshold of occipital cortex excitation between MwA patients and normal controls (C) using transcranial magnetic stimulation(TMS). Methods: TMS was performed using the Cadwell MES 10 stimulator. A circular coil 9.5 cm in diameter was applied to the occipital scalp (7 cm above the inion). Stimulator intensity was increased in 10% increments until subjects reported visual phenomena or 100% intensity was reached. Stimulation intensity was then fine-tuned to determine the threshold at which phosphenes were just visualized. Results: Eleven MwA patients, mean age 37 ± 7 years, were compared with 11 C, mean age 37.7 ± 7 years. The difference in the proportion of subjects with phosphene generation between MwA patients and C was significant(MwA patients 100% versus C 27.3%, p = 0.001). The mean threshold level for MwA patients was 44.2 ± 8.6 versus 68.7 ± 3.1 for C( p = 0.0001). All threshold levels for MwA patients were lower than the lowest threshold for C; the MwA patient with the lowest threshold had an aura after stimulation. Conclusions: The threshold for excitability of occipital cortex is lower in MwA patients compared with C. This is a direct neurophysiologic correlate for clinical observations that have indicated hyperexcitability of the occipital cortex in migraineurs.

The present investigation was conducted in an attempt to determine whether selective auditory attention abilities differed between normal subjects and subjects with bothersome tinnitus. Subjects were 37 adults with tinnitus and high-frequency hearing loss (not affecting thresholds at 500 and 1000 Hz) and 15 subjects who were audiometrically and otologically normal. Results suggested that an electrophysiological index of early selective auditory attention (i.e., the negative difference wave, Nd) was of greater magnitude in tinnitus patients. Also, the cortical NI component occurred significantly later in the presence of selective attention in tinnitus subjects only. Results of this investigation may support the view that early selective auditory attention in subjects with bothersome tinnitus differs from that of normal subjects.

A great deal of information about the characteristics of components N1m and P2m of the auditory evoked cortical fields (AEFs) has accumulated since the late 1970s. However, a number of fundamental issues have not been addressed. For instance, some previous investigators have suggested that P2m is present consistently in normals, whereas others suggest that when present, P2m is small in amplitude. Preliminary observations in this laboratory suggested that P2m is not observed consistently in normal subjects. Therefore, the specific aim of this investigation was to estimate the frequency of occurrence of the contralaterally recorded N1m and P2m after stimulation of right and left ears in normal subjects. Results demonstrated N1m to be present in all circumstances. Consistent with our preliminary observations, P2m was often absent, and moreso after stimulation of the left ear.

We sought to evaluate the utility of quantitative sensory testing (QST) and nerve conduction velocity (NCV) studies as measures of distal symmetric polyneuropathy (DSP). We studied 36 diabetic patients divided into four clinical categories of increasing severity. QST included thermal testing and vibration thresholds. NCV studies included median, peroneal, and sural nerves. Results of QST and NCV were compared among clinical groups using survival methodology. The log-rank statistic showed significant differences among the groups; the direction of the differences were consonant with clinical severity. For each diabetic patient, the result of each measurement was classified as normal or abnormal; more diabetic patients had abnormal NCV than either vibration tests or thermal tests. In conclusion, findings of QST and NCV are in keeping with clinical categorization of patients, QST and NCV are complementary tests, and the sural sensory study is the best single predictor of DSP. © 1992 John Wiley & Sons, Inc.

The near-nerve sensory nerve conduction in the medial and lateral plantar nerves was studied in 25 cases of tarsal tunnel syndrome. Sensory nerve conduction was abnormal in 24 cases (96%) The most common abnormalities were slow nerve conduction velocities and dispersion phenomenon (prolonged duration of compound nerve action potentials). These two electrophysiological abnormalities are indicative of a focal segmental demyelination as the primary pathological process in tarsal tunnel syndrome.