Elevated B6 levels and peripheral neuropathies.

Polyneuropathy related to decreased levels of Vitamin B6 are well known. In contrast, the association between elevated levels of pyridoxine and neuropathy is not well described. This study is a retrospective review of patients in our neuromuscular clinic that were found to have elevated B6 levels. Twenty-six patients were found to have elevated serum B6 levels. The mean B6 level was 68.8 ng/ml. Twenty patients (76.9%) reported daily vitamin use. Twenty-one patients (80.8%) reported only sensory complaints. The most common symptoms reported were numbness (96%), burning pain (49.9%), tingling (57.7%), balance difficulties (30.7%), and weakness (7.8%). Nine (out of 26) had an abnormal EMG/NCS. Eight patients had an abnormal quantitative sensory study. We conclude that elevated pyridoxine levels should be considered in the differential diagnosis of any sensory or sensorimotor polyneuropathy.

False positive rate of thoracic outlet syndrome diagnostic maneuvers.

OBJECTIVE: In this study, we aim to determine the false-positive rate & specificity in normal subjects and carpal tunnel syndrome (CTS) patients of five provocative maneuvers used to diagnose thoracic outlet syndrome (TOS). DESIGN/METHODS: We prospectively evaluated subjects with clinical and electrophysiological evidence of CTS as well as normal subjects. All subjects underwent provocative testing by a blinded physician, which included the Adson A & B tests, Costoclavicular maneuver (CCM), Elevated arm stress test (Roos), and Supraclavicular pressure (SCP). RESULTS: In the CTS group, false positive tests were observed in 42% in the Adson A test, 45% in the Adson B test, 48% in the CCM, 77% in the Roos test, and 61% in the SCP 94% of the CTS patients had at least 1 positive TOS diagnostic maneuver. In the normal group, false positive tests were observed in 9% in the Adson A test, 20% in the Adson B test, 16% in the CCM, 47% in the Roos test, and 30% in the SCP 56% of the normal patients had at least 1 positive TOS diagnostic maneuver. CONCLUSIONS: We conclude that current provocative maneuvers used to diagnose TOS result in a high false-positive rate in normal subjects and an even higher false-positive rate in CTS patients.

Clinical and electrophysiological presentation of pronator syndrome.

Median neuropathy at the elbow (pronator syndrome [PS]) is rare compared to compression at the wrist. We sought to evaluate the clinical/electrophysiological parameters of this focal neuropathy. Between 1992 and 2002, we retrospectively reviewed records of eighty-three limbs in seventy-two patients with PS. Electrodiagnostic data as well as clinical symptoms, physical findings, demographic information and treatment modalities were examined. The main symptoms were forearm pain, numbness and weakness. One patient (two limbs) had nocturnal paresthesias. Twenty-five limbs (30%) showed decreased median forearm velocity. Fifty-four (65%) had abnormal median sensory studies of either abnormal conduction velocity or amplitude. Needle exam showed an abnormality of at least one median innervated muscle, abductor pollicis brevis, flexor carpi radialis, or pronator teres, in 70% (58/83). Sixteen limbs were identified as having undergone surgical decompression. In the surgical group, 10/16 (63%) were found to have constriction with a band which was released during surgery. Eight of the sixteen patients who underwent surgery were found to have documented improvement. Eleven patients (13%) had undergone previous surgery for Carpal Tunnel Syndrome (CTS) without benefit. The clinical and electrophysiological features of PS are quite different from patients with CTS. Proper localization is crucial to treatment options. Surgery can provide benefit in selected cases.

Levetiracetam induced polyneuropathy: a case report.

We report the first case of polyneuropathy induced by levetiracetam, an anti-epileptic medication. Follow up electrodiagnostic studies showed significant improvement after discontinuation of the medication.

Unilateral diaphragmatic paralysis following thoracic outlet surgery: a case report.

In this report, a young female, who initially presented with left upper extremity pain, eventually underwent surgery for presumed thoracic outlet syndrome. Following surgery, she developed shortness of breath. Diagnostic studies revealed an elevated left hemidiaphragm secondary to injury to the phrenic nerve.

Median nerve function in patients undergoing carpal tunnel release: pre- and post-op nerve conductions.

Patients undergoing surgery for carpal tunnel decompression may improve clinically, however it is not well known as to how median nerve neurophysiology is altered following surgery. Fifty patients who underwent open carpal tunnel release were prospectively studied. Each patient underwent nerve conduction studies pre-op and at 6 months post-op. Patients were also asked to answer several questions regarding their clinical symptoms to see how they improved. 48/50 patients had clinical improvement based on their response (resolution of nocturnal paresthesias, decreased sensory complaints and pain). Average pre- and post-op parameters were as follows: distal motor latency (DML) (msec) 5.24/4.42; distal motor amplitude (mV) 8.28/8.64; sensory conduction velocity (m/sec) 38.9/41.0; sensory amplitude (uV) 10.94/15.61. We conclude that the DML and sensory amplitude showed significant improvement following surgery; the sensory conduction velocity remains slow.

Reproducibility of motor unit number estimation in individual subjects.

Although the reproducibility of motor unit number estimation (MUNE) for groups of subjects has been studied, there is little such data for individuals. Prediction intervals represent a tool to study individual MUNE reproducibility and represent the range of values expected for a future MUNE if the true number of motor units remains unchanged. MUNE was performed using the statistical method on 48 normal individuals. The prediction interval was found to be a function of the intrasubject coefficient of variation. Using a commercial manufacturer's recommended technique and software, prediction intervals were found to be so broad as to be of uncertain value. We found that by averaging two MUNE observations for each determination, and using the method of weighted averages for calculating the size of an average single motor unit potential, the intrasubject coefficient of variation was reduced from 16.48% to 8.77%, and the 90% prediction interval became sufficiently narrow to be clinically useful. False-negative rates were also lowered substantially using these techniques. Thus, simple modifications of an existing MUNE program improved the clinical utility of this program for the longitudinal study of patients in whom changes in motor unit number over time are of importance, such as those with motor neuron diseases.

Benzodiazepine toxicity with profound suppression of the electroencephalogram.

The authors report the case of a 60-year-old man with respiratory distress secondary to exacerbation of chronic obstructive pulmonary disease, right lower lobe pneumonia, and severe bronchospasm. High doses of lorazepam were given intravenously after failure to control bronchospasm and agitation with bronchodilators and mucolytic agents; the patient was unresponsive to all stimuli while receiving lorazepam. Electroencephalography revealed a profoundly suppressed pattern without accompanying low-voltage fast activity--this was reversible following withdrawal of the lorazepam.

Basilar artery dissection in a young woman: a case report.

The case of a young woman with basilar artery dissection, possibly precipitated by trauma, is presented, and the literature is reviewed.

Ulnar neuropathy at the wrist.

Compression of the ulnar nerve at the level of the wrist is rare and often difficult to diagnose. This article describes the various types of lesions that may occur and discusses the different electrophysiologic techniques that may aid the electromyographer in localizing lesions to the wrist.

Relationships between clinical symptom severity scales and nerve conduction measures in carpal tunnel syndrome.

This study examined the severity of symptoms in carpal tunnel syndrome (CTS) in relation to nerve conduction measures of the median nerve. Clinical symptom severity and nerve conduction studies were evaluated for 64 hands with CTS in 45 patients. We found the following: (1) significant relationships identified among the clinical scales resulted in a dichotomous symptom classification scheme into primary and secondary symptoms, with the former being more specific for those symptoms usually seen in association with nerve injury; (2) there were significant relationships between symptom severity and nerve conduction abnormality; (3) the primary symptom scale correlated more strongly with the electrodiagnostic measures of nerve injury than did the secondary symptom scale. Based on these findings, we believe that these clinical scales have biological significance and reflect median nerve injury. This would support their potential utility for evaluating the outcome of CTS treatment and developing a model for exposure-severity relationship.

Localized hypertrophic neuropathy: magnetic resonance imaging findings and long-term follow-up.

Four patients with painless, progressive focal neurological deficits that localized to peripheral nerve or plexus were eventually found to have the relatively rare condition of localized hypertrophic neuropathy or intraneural perineurioma. Magnetic resonance imaging (MRI) was an excellent tool for aiding in the precise localization of the lesion, if specifically tailored with regard to imaging planes and specific MRI sequences. Fat-saturated T2-weighted and fat-saturated T1-weighted postgadolinium images provided the best visualization, particularly with a high-field magnet and phase array body coil. Two patients stabilized following resection of the lesion and sural nerve grafting, and 1 had partial improvement in a proximal muscle following neurolysis.

Electrodiagnostic studies: are they useful in clinical practice?

OBJECTIVE: Electrodiagnostic testing (electromyography [EMG] and nerve conduction studies [NCS]) may result in some patient discomfort. The justification for such testing should be based on the expectation that the results will affect patient management. This study was conducted to determine how frequently the results of EMG/NCS change the clinical management of the patient. METHODS: One investigator (MB) spoke to each referring physician after EMG/NCS to determine if any management decisions were altered by the test. RESULTS: One hundred forty consecutive EMG/NCS records were obtained. Follow-up was available on 100 patients. Of 78 patients with abnormal findings on EMG/NCS, 29 (37%) had a diagnosis different from the referring diagnosis. For 43 of the 78 (55%), the physician reported that additional diagnostic testing was undertaken or treatment plans were altered. CONCLUSION: EMG/NCS are useful, informative, and diagnostic in the management of various neurologic disorders.

Medial antebrachial cutaneous sensory studies in the evaluation of neurogenic thoracic outlet syndrome.

Over 3 years, we studied 8 patients with neurogenic thoracic outlet syndrome (TOS) and tested the medial antebrachial sensory response (MASR) to determine its diagnostic value. The MASR and ulnar sensory response (USR) were abnormal in all 8 patients. Seven had a low median motor response (MMR) with a low USR. In 1, the MASR and USR were abnormal but the MMR was normal. We conclude that the MASR is of diagnostic value in patients with neurogenic TOS.

Three ulnar nerve conduction studies in patients with ulnar neuropathy at the elbow.

OBJECTIVE: Ulnar neuropathy at the elbow is often difficult to localize by standard electrophysiologic testing. This study compared three ulnar nerve conduction studies to determine which was more sensitive in localizing ulnar neuropathy at the elbow. METHODS: Motor studies to the first dorsal interosseous and the abductor digiti quinti and a mixed ulnar nerve sensory study across the elbow. RESULTS: Motor studies to the first dorsal interosseous and abductor digiti quinti were abnormal in 81% and 71% of patients, respectively. The ulnar mixed sensory study across the elbow was abnormal in 57%. In 38%, all three tests were abnormal. CONCLUSION: Motor studies were more sensitive than the ulnar mixed sensory study across the elbow in localizing ulnar neuropathy of the elbow.

Sural/radial amplitude ratio in the diagnosis of mild axonal polyneuropathy.

As proximal nerves are relatively spared in length-dependent, axonal polyneuropathy, we theorized that a sural/radial amplitude ratio (SRAR) might be a sensitive indicator of mild polyneuropathy. In this study, sural amplitudes and SRARs in patients with signs of mild axonal polyneuropathy were compared to those of normal, age-matched control subjects. Sural and radial sensory responses were measured in a standard fashion in all subjects. Thirty polyneuropathy patients had an average SRAR of 0.29 as compared to 0.71 for the 30 normal subjects. An SRAR of less than 0.40 was a strong predictor of axonal polyneuropathy, with 90% sensitivity and 90% specificity, as compared to an absolute sural amplitude of less than 6.0 microV, which had sensitivity of only 66%. Additionally, unlike the sural amplitude, the ratio did not vary significantly with age. We conclude that the SRAR is a sensitive, specific, age-independent electrodiagnostic test for mild axonal polyneuropathy.

Bilateral facial palsy secondary to herpes zoster meningoencephalitis in a HIV-positive woman.

Bilateral facial paralysis of diverse infectious aetiologies has been reported in HIV infected patients. We present a patient with bilateral facial palsy most likely due to herpes zoster meningoencephalitis in a patient with neutropenia and who subsequently tested HIV-positive.

Nerve, muscle, and neuromuscular junction electrophysiology at high temperature.

Although the effect of low temperature on the peripheral nervous system has been systematically studied, the effect of high temperature has not. We investigated the effect of elevating limb temperature from 32 degrees C to 42 degrees C by performing sequential motor studies, antidromic sensory studies, and 3-Hz repetitive stimulation in normal subjects. In addition, we recorded single motor units by using threshold stimulation. On average, motor amplitude and duration decreased by 27% and 19%, respectively, whereas sensory amplitude and duration decreased by 50% and 26%, respectively. Neuromuscular transmission remained normal at 42 degrees C. Single motor unit recordings revealed a reduction in amplitude of 26%, similar to the overall reduction in compound motor amplitude. These findings demonstrate that significant reductions in sensory and motor amplitudes can occur in normal nerves at high temperature; we hypothesize that these changes are secondary to alterations in nerve and muscle ion channel function.