Muscle & nerve
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We report electrophysiological findings of conduction along peripheral sensory fibers in 64 patients with amyotrophic lateral sclerosis. Distribution of the values of action potential amplitudes and conduction velocities of peripheral afferent fibers were significantly lower than in normal age-matched controls. Sensory action potential amplitudes (SAPas) were more affected than sensory conduction velocities (SCVs). ⋯ A parallel decrease in SCVs and MCVs in 14 patients in whom the study was repeated over a period of time was also found. All these electrophysiological findings are due to progressive neuronopathy of peripheral sensory fibers. A pathogenetic mechanism is proposed.
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Review Case Reports
Case-of-the-month: painful thigh mass in a young woman: diabetic muscle infarction.
A 29-year-old female with type I diabetes mellitus developed pain, focal tenderness, and swelling in the posterior left thigh. Subsequent evaluation included a muscle biopsy, which revealed large confluent areas of necrosis and edema, compatible with a diagnosis of diabetic muscle infarction (DMI). Diabetic muscle infarction (DMI) is an unusual neuromuscular complication of diabetes mellitus. ⋯ The focal region of muscle damage can be noninvasively viewed by magnetic resonance imaging and radionuclide scans. Muscle biopsy demonstrates large confluent regions of muscle necrosis and edema. DMI needs to be differentiated from other processes that can cause leg pain in a diabetic patient.
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Case Reports Comparative Study
Stimulated single-fiber electromyography in Lambert-Eaton myasthenic syndrome.
The Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of neuromuscular transmission. Electrodiagnosis is confirmed by an increase in compound muscle action potential amplitude during high-frequency repetitive nerve stimulation or following brief exercise. We describe the results of stimulated single-fiber electromyography in 4 patients with disorders of neuromuscular transmission: LEMS (2), LEMS/myasthenia gravis (MG) overlap (1), and MG (1). ⋯ In all 4 patients, a rate dependence of jitter was found. In LEMS and LEMS/MG, jitter and blocking improved with high stimulation rates, as compared with the opposite effect in MG. We conclude that stimulated SFEMG is a valuable technique in the diagnosis of LEMS.
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Reported here are the electrodiagnostic findings in a patient with myasthenia gravis who had dysarthria, dysphagia, and dyspnea. The use of repetitive nerve stimulation and single fiber electromyography studies for the evaluation of patients suspected of myasthenia gravis is reviewed.
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Case Reports
Mononeuropathy in sickle cell anemia: anatomical and pathophysiological basis for its rarity.
Peripheral neuropathy is a rare complication of sickle cell disease. We report a young black woman with sickle cell anemia who developed a proximal median mononeuropathy in the setting of sickle cell crisis. The clinical and electrodiagnostic features are consistent with an ischemic mechanism from the sickling process. The pathophysiological basis for the rarity of this complication may be related to the rich anastomotic microvasculature of peripheral nerve and the unique large size of the capillaries of this vascular network.