Sonography in carpal tunnel syndrome with normal nerve conduction studies.

INTRODUCTION: We assessed the yield of high-resolution ultrasonography (HRUS) in patients with clinically definite carpal tunnel syndrome (CTS) and normal nerve conduction studies (NCS). METHODS: This blinded, prospective, cross-sectional study involved 35 patients (60 hands) with clinically definite CTS and normal NCS, and 20 controls (40 hands). Cross-sectional area (CSAs) of the median nerve at the level of the pisiform bone and flexor retinaculum thickness (FRT) were measured. RESULTS: CSA was abnormal in 48.6% of patients (confidence interval 32.0-65.2%, P = 0.95). FRT was increased in only 34.3% (18.3-49.7%), but was independently abnormal in 2 patients. CSA abnormalities correlated with positive provocative tests and sensory loss. The HRUS changes were mild. CONCLUSIONS: HRUS confirms clinically diagnosed CTS in about half of the patients with normal NCS.

Clinically definite ALS presenting weeks after mild electric injury: causality or coincidence?

Motor neuron syndromes including typical ALS develop very rarely after electrotrauma, with possible causality discussed but not confirmed. We report on a 44-year-old male who developed clinically definite ALS by the revised El Escorial criteria with onset weeks after mild electric injury. He presented with asymmetric upper limb amyotrophy and weakness beginning around the entry point of the current. Over 1 year he developed generalized wasting, weakness and fasciculations, including the bulbar and thoracic muscles, with prominent spasticity and pyramidal tract signs. Electrodiagnostic studies confirmed widespread denervation, very unstable neurogenic motor units in the bulbar, cervical, thoracic and lumbosacral segments with normal motor velocities and normal sensory parameters. This is a well-documented case of fast-progressive ALS that seems related to electric injury.

Single-fiber electromyography of facial and limb muscles in diabetic patients with or without neuropathy.

PURPOSE: In diabetic patients, single-fiber electromyography (SFEMG) is often abnormal in the limb muscles and is considered unreliable in diagnosis of synaptic disorders. We aimed to compare SFEMG abnormalities of frontalis muscle (FM) and extensor digitorum communis muscle in diabetic patients with neuropathy and without neuropathy. METHODS: Stimulation SFEMG of FM and extensor digitorum communis muscle was performed in matched groups of 30 diabetic patients with neuropathy and 20 diabetic patients without neuropathy. RESULTS: Single-fiber electromyography in the FM was abnormal in four diabetic patients with neuropathy and in one diabetic patient without neuropathy. Changes were rather mild. Extensor digitorum communis abnormalities were significantly more frequent-in 20 diabetic patients with neuropathy and in 7 diabetic patients without neuropathy (P < 0.001). We never observed a patient with abnormal FM but normal extensor digitorum communis muscle. CONCLUSIONS: In diabetes, FM exhibits rare and quite mild SFEMG changes. This muscle may be suitable for SFEMG in diabetic patients with clinical suspicion for synaptic disorder.

Iatrogenic femoral neuropathy: two cases and literature update.

Iatrogenic femoral neuropathy is an uncommon surgical or obstetric complication that may be underreported. It results from compression, stretch, ischemia, or direct trauma of the nerve during hip arthroplasty, self-retaining retractor use in pelvicoabdominal surgery, lithotomy positioning for anesthesia or labor, and other more rare causes. Decreasing incidence of this complication after abdominal and gynecologic surgery but increase in its absolute numbers after hip arthroplasty has emerged over the last decade. We describe two illustrative cases related respectively to lithotomy positioning and self-retaining retractor use. The variability in clinical presentation of iatrogenic femoral nerve lesions, some new insights in their diverse pathophysiology, and in the diagnostic and treatment options are discussed with an update from the literature.

Single-fiber electromyography of masseter muscle in myasthenia gravis.

Jitter after axonal microstimulation in the masseter muscle was studied in 30 consecutive patients (12 women) with myasthenia gravis (MG). Patients' mean age was 42.3 (12-75), median disease duration was 3 months (1-72), and onset was ocular (15 cases), oculobulbar (7), bulbar (6), or generalized (2). There were 23 newly-diagnosed patients. Nine cases developed purely ocular MG and 21 cases developed generalized MG. In the latter group, five subjects had a rapidly progressive course and 16 subjects had stable or well-controlled disease (MGFA grade 2-3). Six patients did not have circulating anti-acetylcholine receptor antibodies. Masseter single-fiber electromyography (SFEMG) was abnormal in 6 of 9 ocular MG patients and in all generalized cases (overall sensitivity 27 of 30 cases or 90%; confidence interval 79.3%-100.0% at P = 0.95). Masseter should be considered for SFEMG in diagnosis of MG, especially in cases with bulbar onset.

Stimulated jitter in the masseter muscle: normative values.

Nineteen healthy volunteers (median age, 25; range, 18-51 years) were enrolled in a study to obtain normative values for stimulated jitter in the masseter muscle. Axonal microstimulation was performed via a monopolar needle electrode introduced in the masseter 2-2.5 cm above the mandibular angle on the line connecting it with the lateral canthus. The recording single-fiber electromyography (SFEMG) electrode was inserted anteriorly in the twitching area of the muscle. The mean consecutive difference (MCD) values for the 426 endplates studied followed a distribution skewed to the left, with a minimum value of 4.3 micros, maximal 44.7 micros, and a maximum of distribution at 11 micros. Mean pooled MCD measured 16.0 micros, and the mean of mean MCD per study was 13.6 micros. The value of the 95th upper percentile for an individual fiber was 29.3 micros. We suggest an upper normal limit for mean MCD per study of 21 micros and upper normal limit of MCD for individual fibers of 30 micros. The stimulated jitter study of masseter muscle is easy and reliable.