Nerve conduction studies

Differential diagnoses of peripheral neuropathy were entertained. Laboratory tests revealed that serum parameters for electrolytes and proteins were all within the normal range. Urine porphyrinogen and porphobilinogen levels were normal. Tests were negative for serum rheumatoid factor and antinuclear antibodies, the latter used in detection of connective tissue diseases such as systemic lupus erythematosus and polyarteritis nodosa that could present with features of peripheral neuropathy. Nerve conduction studies of the radial, ulnar, and median nerves revealed delayed conduction. Biopsies of the ulnar and radial nerves showed loss of nerve fibers and sudanophilic (indicating lipid) deposits in the Schwann cells of the neurons. Similarly, the yellowish plaques of the pharynx showed abundant macrophages filled with sudanophilic material. These deposits were not membrane-bound. 

Nerve conduction study. This tests for specific muscle fatigue by repetitive nerve stimulation. It should demonstrate decrements of the muscle action potential due to impaired nerve-to-muscle transmission. 

The history and physical examination provide the foundation for the diagnosis and should demonstrate the combination of lower motor neuron (LMN) involvement, manifested by weakness and muscle atrophy, and upper motor neuron (UMN) involvement, evidenced by increased tone and hyper-reflexia, in at least three areas, including the Umbs, tongue, and back muscles. Needle EMG and nerve conduction studies should be performed to confirm the diagnosis in aU patients with suspected ALS. 

An 87-year-old patient with resistant nodnlar pmrigo was successfully treated with ciclosporin (3 mg/kg/day) and prednisone (10 mg/day) (29). Bilateral nnmbness and distal limb weakness developed after 18 months. Clinical examination, electromyography, and nerve conduction studies confirmed a diffnse axonal nenro-pathy which rapidly progressed over the next 2 months. Ciclosporin alone was withdrawn and complete remission was observed within 3 months. 

The importance of the patient s position has been illustrated by a study in which transient neurological symptoms occurred in five of 12 volunteers who were given 5% lidocaine 50 mg intrathecaUy and then placed in the low lithotomy position (251). No consistent abnormalities were detected by prespinal and postspinal electromyography, nerve conduction studies, or somatosensory evoked potentials. This is in line with the current opinion that transient neurological symptoms constitute neither a true neurological syndrome nor an expression of the neurotoxicity of local anesthetics. 

Nitrous oxide inactivates the enzyme methionine synthetase, and caution is urged in giving nitrous oxide to patients who may be deficient in vitamin B12. Low serum vitamin B12 concentrations have previously been reported in patients with sickle cell disease, but the reason for this is uncertain. Three cases of peripheral neuropathy have been reported in patients with sickle cell disease who received nitrous oxide (12-14). AU three had a history of frequent painful sickle crises, for which they received nitrous oxide for prolonged periods. Serum vitamin B12 concentrations were slightly reduced in two patients and very low in the third. The patients aU presented with difficulty in walking and paresthesia. Peripheral sensorimotor neuropathy was confirmed by nerve conduction studies. The patients all responded well to vitamin B12 injections and avoiding further exposure to nitrous oxide. Caution is therefore recommended when using nitrous oxide in patients with sickle cell disease or who are suspected of vitamin B12 deficiency. Two cases of polyneuropathy have also been reported after the use of nitrous oxide for 80 minutes and 3 hours in patients who were subsequently found to have pernicious anemia. They both responded well to hydroxocobalamin. 

Riggs JE, Ashraf M, Snyder RD, Gutmann L. Prospective nerve conduction studies in cisplatin therapy. Ann Neurol 1988 23(l) 92-4. 

Sensory neuropathy was reported as an adverse effect in eight patients with homocystinuria who took 600-1200 mg/day of pyridoxine for 4-22 years. Nerve conduction studies of the sural nerve in five affected patients showed abnormalities in four (21). Neuropathies have been observed in women taking doses as low as 50-500 mg/day for one to several months (22,23). 

Changes in nerve conductivity are frequent and predictable in thalidomide-induced neuropathy. Nerve conduction studies are required before and during therapy, irrespective of dose (55). 

Snyder R, Seelinger D. 1976. Methylmercury poisoning Clinical follow-up and sensory nerve conduction studies. J Neurol Neurosurg Psychiatry 39 701-704. 

The women initially complained of numbness in their limbs, and subsequent nerve conduction studies showed alterations in peripheral nerve activity. The effect was diagnosed as primarily a distal sensory peripheral neuropathy. These cases were unusual because the effect was greater in the hands than in the feet, the reverse of most peripheral neuropathies. Sural nerve biopsies in two of the women performed 3-4 years after diagnosis revealed chronic neuropathy (axonopathy and myelinopathy) (Liss 1988). The authors did not establish a causal relationship with 1,1,1-trichloroethane. 

List of Abbreviations HSAN, Hereditary sensory and autonomic neuropathies HSN, Hereditary sensory neuropathies NCS, Nerve conduction studies QST, Quantitative somatosensory testing... 

Nerve conduction studies—Measurement of the speed of electrical conduction through a nerve. 

This appendix described four types of tests that have been used to assess the neurotoxicity potential of jet-propulsion fuel 8 and related fuels in humans clinical neurological examinations, posturograms, nerve conduction studies, vibration sensation studies, and blink reflex classical conditioning studies. For each test, a critical analysis ofits use in assessing neurotoxicity from exposure to jet fuels is presented. Limitations of these tests are also presented. 

Nerve conduction studies have been used extensively to study peripheral nerve function. These tests have been shown to be valid marker of nerve damage and a correlated with pathological findings. These tests have been... 

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