The contribution of oculography to early diagnosis of myasthenia gravis

Summary

Saccadic eye movements were examined by infrared reflection oculography in 22 patients with suspected myasthenia gravis. In all of them the diagnosis was confirmed either by electromyography, by the presence of acetylcholinereceptor antibodies (15 cases), by a positive clinical Tensilon test (4 cases), or by the course of the disease (3 cases). The aim of the study was to find out which of the saccade disorders described in myasthenic patients can be found in the early stage of the disease, and to discover their diagnostic value. Typically, saccade abnormalities were also seen in clinically uninvolved eyes. Intrasaccadic disorders mainly consisted of “decrescendo” of the velocity profiles (two-thirds of the cases) and “hypometria” (half of the cases). Postsaccadic “waver” was present in about two-thirds of the patients. The most frequent finding was “intersaccadic variation” (i.e., variation between repeated corresponding saccades) which occurred in 18 of the 22 patients, and particularly affected the velocity profiles. A standardized fatigue test proved to be useful in accentuating mild, or provoking latent pathology in most of the patients. A standardized combined examination of saccades with Tensilon yielded pathological results less frequently than hitherto described in the literature. In 4 of the 9 patients with purely ocular myasthenia gravis oculography led to the diagnosis. The problems in attempting to delimit the observed saccade abnormalities from those found in other eye movement disorders are discussed.