Y.F. Dan

Repetitive hypoglossal nerve stimulation in myasthenia gravis.

OBJECTIVES To assess the diagnostic efficacy of repetitive nerve stimulation (RNS) of the hypoglossal nerve in patients with myasthenia gravis (MG) and bulbar symptoms (dysphagia, dysarthria). METHODS Twenty patients with MG and 25 normal controls had RNS of the hypoglossal nerve. All patients also had single fibre electromyography (SFEMG) of the orbicularis oculi and RNS with recordings of the nasalis, trapezius and abductor pollicis brevis muscles. RESULTS All patients had positive SFEMG studies. Nine patients with bulbar symptoms had positive hypoglossal RNS, including 3 with negative RNS recordings in other muscles. Eleven patients with no bulbar symptoms showed negative hypoglossal RNS, including two with positive RNS recordings from other muscles. CONCLUSIONS Abnormal RNS of the hypoglossal nerve correlates well with bulbar dysfunction and further characterises the extent of neuromuscular transmission defect in MG patients.

Decrement in area of muscle responses to repetitive nerve stimulation

Measurement of the decremental muscle response to repetitive nerve stimulation (RNS) has low yields for the diagnosis of neuromuscular transmission defects compared with single fiber electromyography (SFEMG). We compared area and amplitude of muscle responses to RNS in 87 patients and 30 controls, using SFEMG as the reference standard. Decrement of response area provided additional diagnostic yields of 5.3% to 30% depending on the muscle examined and disease severity, and is recommended as a diagnostic adjunct to measurement of amplitude decrement during RNS. Muscle Nerve 27: 494–496, 2003

Clinical and electrophysiological aspects of distal ulnar neuropathy

Objectives– To evaluate the use of fixed distance side to side comparison of abductor digiti minimi (ADM) and first dorsal interosseous (FDI) compound muscle action potential (CMAP) studies in the diagnosis of distal ulnar neuropthy. Materials and methods– Thirty normal controls underwent ADM and FDI CMAP studies bilaterally at a fixed ADM recording to stimulating point distance of 6 cm. Side to side mean latency differences to both muscles were calculated. Twenty patients with suspected unilateral distal ulnar neuropathy from routine nerve conduction studies had positive results when compared with controls. Results– The upper limit of normal for side to side mean latency difference at 3 SD above the mean was 0.394 and 0.474 ms for ADM and FDI, respectively. All 20 patients had side to side mean CMAP latency difference above 3 SDs in the ADM, FDI or both muscles. Fifty percent of cases had involvement of the superficial sensory branch. Conclusions– Fixed distance side to side CMAP latency comparison is a useful electrodiagnostic adjunct for distal ulnar neuropathy. Trauma was the most common aetiology in the 20 reported cases. Correlation was found between aetiological factors and sites of lesions as localized with this method.

Rapid ultrasonographic diagnosis of radial entrapment neuropathy at the spiral groove

BACKGROUND Entrapment neuropathy of the radial nerve at the spiral groove region is relatively common. However, its localization may be technically challenging. OBJECTIVE To evaluate the use of ultrasound (US), in relation to electrophysiological testing, for this purpose. METHODS We studied 32 normal controls to obtain US parameters of the radial nerve. In addition, 10 patients with suspected radial neuropathy were tested using US and electrophysiological techniques. RESULTS US examination correctly identified all 6 patients with radial neuropathy. The other 4 patients with alternate diagnoses did not show US abnormalities exceeding that of normal controls. US examination required a significantly shorter time than electrophysiological testing. CONCLUSIONS US is of value as a rapid diagnostic adjunct for the localization of radial nerve entrapment.

Sensitivities of sensory nerve conduction study parameters in carpal tunnel syndrome.

Summary: It is generally accepted that median sensory nerve conduction studies are more sensitive than motor nerve conduction studies in the electrodiagnostic evidence of carpal tunnel syndrome (CTS). This study was conducted to compare the sensitivities of various parameters of sensory nerve conduction studies in the diagnosis of CTS.This prospective study included 88 consecutive patients (151 hands) with CTS and 106 control subjects. CTS was diagnosed clinically by two neurologists. Median sensory nerve responses with wrist stimulation were determined. The onset and peak latencies, peak-to-peak amplitudes, negative peak duration, and area were measured. The differences between the peak and onset latencies were also calculated as a measure of waveform temporal dispersion. Among each measured parameter, values between the 2.5th and the 97.5th percentile range of the control subjects served as the normal limits.Among the 151 hands with suspected CTS, five (3.3%) had normal electrodiagnostic studies and 146 (96.7%) had at least one abnormal electrodiagnostic study. Among the 146 hands with an abnormality, 138 had abnormal onset latency, 143 had abnormal peak latency, and 88 had abnormal difference between peak and onset latency. In addition, 87 had abnormal amplitude, 70 had abnormal duration, and 59 had abnormal area. The sensitivity was 91.4% for onset latency, 94.7% for peak latency, 58.3% for difference between peak and onset latency, 57.6% for amplitude, 46.4% for duration, and 39.1% for area.Our study shows that in patients with CTS, the most sensitive sensory nerve conduction parameter is the peak latency. Studying various additional sensory nerve conduction parameters did not significantly increase the diagnostic yield.

Superficial peroneal sensory and sural nerve conduction studies in peripheral neuropathy

The objective of this study was to prospectively evaluate sensory nerve conduction studies (NCS) in the distal lower limbs in the electrodiagnosis of peripheral neuropathy. We prospectively studied 316 consecutive patients with surface stimulation and recording, in comparison with 90 control subjects. A total of 310 patients were found to have lower limb sensory NCS abnormalities. In these patients, the rate of detection of peripheral neuropathy with superficial peroneal NCS (88.5%) was significantly higher (P<0.001) compared with sural NCS (75%). The superficial peroneal NCS appeared to have a higher detection rate for peripheral neuropathy in our study, and its study can be adjunctive to sural NCS.

High-resolution ultrasound in the evaluation and prognosis of Bell's palsy.

Introduction:  Bell’s palsy is a commonly encountered paralysis of the facial nerve occurring worldwide. Prognosis for Bell’s palsy is good, but the proportion of patients with poor outcomes may reach 30%. Ultrasound (US) may provide a novel approach for evaluating and prognosticating Bell’s palsy, in comparison with known electrophysiological techniques.

Cutaneous silent periods in the evaluation of cord compression in cervical spondylosis

ObjectiveThe clinical diagnosis of cervical spondylotic myelopathy (CSM) may be challenging in patients with cervical spondylosis (CS). Routine nerve conduction studies (NCS) may not evaluate cord compression adequately.MethodsWe obtained cutaneous silent periods (CSP) in 26 consecutive patients presenting with clinical features of CS, in comparison with 30 normal controls. The results were also compared with transcranial magnetic stimulation (TMS) findings, and magnetic resonance imaging of the cervical cord as the gold standard.ResultsCSP findings showed similarly high sensitivity of up to 96% with TMS in evaluating cervical cord dysfunction.ConclusionIn specific clinical settings, CSP is of value for the diagnosis of CSM in CS. CSP measurement is advocated as a simple and rapid diagnostic adjunct to NCS in evaluating CS patients with possible cord compromise.

Short-segment nerve conduction studies in the localization of ulnar neuropathy of the elbow : Use of flexor carpi ulnaris recordings

Short‐segment nerve conduction studies were performed in 17 limbs with clinical features suggestive of ulnar neuropathy at the elbow. Recording from flexor carpi ulnaris yielded 93% sensitivity, compared with 71.4% when recording from abductor digiti minimi. The rationale underlying the technique is discussed. This approach should be of value as a diagnostic adjunct in technically challenging cases of ulnar neuropathy at the elbow. Muscle Nerve, 2005

The value of bilateral ipsilateral and contralateral motor evoked potential monitoring in scoliosis surgery

Intraoperative monitoring (IOM) of the motor pathways is a routine procedure for ensuring integrity of corticospinal tracts during scoliosis surgery. We have previously demonstrated presence of ipsilateral motor evoked potentials (MEPs) during IOM for scoliosis surgery, but its significance was uncertain. In this case series, we show concurrent ipsilateral and contralateral MEP amplitude changes obtained with cortical stimulation are of value in reducing false positive observations during IOM. The use of this easily recordable MEP is thus advocated as a diagnostic adjunct to contralateral MEPs for scoliosis and spinal surgery.