Muscle electromyography

Reflex action can be objectively examined. Measurement of the so-called electrical conduction velocity of motor nerves gives an indication of whether peripheral nerves have been damaged. Electromyography, or examination of the electrical activity of the muscle, and electroencephalography (EEG) can also be used to detect the presence of neurologic abnormalities. And, at least in animal tests, detailed pathological examination of neural tissue can be performed on animals that are killed. 

A 45-year-old man in otherwise good health complains of muscle weakness early in the morning but says it is less of a problem as the day goes on. The neurologist performs electromyography and notes no alteration in nerve conduction velocity but does observe facilitation in the compound action potential with repetitive 50-Hz stimulation. This indicates a defect at the prejunctional side of the neuromuscular junction. Which of the following is a possible cause ... 

Rodrequez, A.A., Agre, J.C., et al.(1993) Acoustic myography compared to electromyography during isometric fatigue and recovery. Muscle and Nerve 16 188-192... 

Electromyography and saccadic velocity studies demonstrated that the mechanical restriction of the eye is caused by interstitial edema and fibrosis of the muscles rather than by myopathy. However, in the acute phases of Graves orbitopathy saccadic velocity testing demonstrates a neuropathic state, which resolves on fibrosis. 

Dermatomyositis, with typical clinical effects, biochemical tests, electromyography, and muscle biopsy, occurred in a 75-year-old man who had taken alfuzosin for 1 year (7). There was no mahgnancy and he recovered fully after alfuzosin withdrawal (timing not given). 

Amiodarone-induced neuromyopathy has been studied in three patients by a review of their records, electromyography, and histopathology of muscle and nerve (95). Two patients had a slightly asymmetric, mixed, but primarily... 

A 34-year-old man with scleromyxedema had flu-like symptoms and muscle pain after the first injection of interferon alfa 6 MU (312). After three additional injections at 2-day intervals, his muscle symptoms worsened and were associated with mild quadriparesis, reduced deep tendon reflexes, dark urine, confusion, and agitation. Biological findings were consistent with acute rhabdomyolysis, and electromyography showed rare denervation potentials. His symptoms resolved and the laboratory findings normalized within 15 days. 

Confirmatory tests for IMS include persistent inhibition of AChE, decreasing response on electromyography, and necrotizing myopathy on muscle biopsy. In most instances, recovery from IMS is complete, though a few deaths have been reported due to severe respiratory insufficiency. Only a few IMS patients have developed delayed neuropathy. The risk of death in IMS is as dangerous as it is in the cholinergic crisis phase. Due to development of severe respiratory distress, tracheostomy is recommended for ventilatory support. Patients may remain on a respirator for 7 days or more. In conclusion, prolonged inhibition of... 

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