Voice spectrography in the evaluation of myasthenia gravis of the larynx.

Myasthenia gravis is a neuromuscular disorder that affects striated muscles especially those innervated by the cranial nerves. The standard diagnostic regimen is to find a reversal of symptoms by acetylcholine esterase administration. The permanent and objective recording of this effect is the key to an accurate assessment of this test. The voice spectrograph is a noninvasive means of evaluating the voice. It has been used successfully to make a clear and specific diagnosis of myasthenia gravis as it affects the larynx. The test can be used to distinguish myasthenia gravis from other functional, anatomical and neuromuscular laryngeal disorders.