[Standard electromyography for the diagnosis and prognosis of laryngeal neuromuscular disorders].

The clinical use of the laryngeal electromyography is still scanty; nevertheless, in our experience it has been shown to be an efficient and objective test in the study of the neurological disorders of the larynx and in the prognosis of recovery after vocal cord paralysis. We have performed conventional electromyography of the thyroarytenoid and cricothyroid muscles in 25 patients with laryngoscopically--confirmed vocal cord paralysis of different etiology. Positive sharp waves, fibrillation potentials and decreased or absent activity on maximal voluntary effort provided enough evidence of denervation in those cases of neurogenic origin. An increased number of polyphasic potentials and increased length of the motor unit potentials recruited in reduced interference patterns were considered suggestive of reinervation, which has an outstanding prognostic value on laryngeal neuropathy. Voluntary motor units, even in some clinically non-mobile vocal cords, were identified in recruitment patterns. Laryngeal electromyography can be done as an office procedure with a minimum of discomfort. It gives objective evaluation of the neuromuscular status, and shows direct evidence of cord function, being useful to distinguish from supranuclear and mechanical disorders of the larynx. It has also shown to be efficient as recovery predictor after vocal cord paralysis.