[Optokinetic nystagmus and the Tensilon test in myasthenia]

Horizontal optokinetic nystagmus was measured before and after the intravenous administration of 10 mg of Tensilon in 12 patients with myasthenia gravis; 11 patients showed an increase of amplitude; this measure seems to be a reliable test for the diagnosis of myasthenia but the increase of frequency of optokinetic nystagmus is less specific. The increases of amplitude in the same patient may show important variations between the two eyes and depending on the direction of nystagmus; however, the greatest response is often observed in the optokinetic nystagmus which was initially the weakest.