CHANGES IN PSYCHOPHYSIOLOGICAL PROCESSING OF VISION IN MYASTHENIA-GRAVIS

Objective. To investigate the possibility of impaired central nervous system (CNS) cholinergic transmission in myasthenia gravis (MG), and t he effect of eye movements and particularly of micromovements in the p sychophysiology of vision. Materials and Methods: Fourteen patients wi th clinical manifestations of external ophthalmoplegia due to differen t causes (nine patients with myasthenia gravis and five with ocular my opathy) were examined. Simultaneous recording of eye movements (optica l method) and pattern reversal-visual evoked potentials (PR-VEPs) were performed. Results: Eye micromovements during fixation were impaired in both groups. A statistically significant difference (P < 0.01) was found in the amplitude of P100 of PR-VEPs before and after treatment i n MG patients, and also between normal controls and MG patients before (P < 0.001) and after treatment (P < 0.01). P100 latency of the PR-VE Ps in MG patients before and after treatment was delayed compared to n ormal controls, while there were no differences between ocular myopath y patients and normal controls. Conclusion: The eye movement impairmen t observed in MG patients is not sufficient to explain abnormal PR-VEP s detected.in these patients. These results provide neurophysiological evidence of impaired cholinergic transmission in the central nervous system in patients with MG and suggest that PR-VEPs offer an easily ap plicable non-invasive method to study the central effects of MG. (C) 1 998 Published by Elsevier Science B.V. All rights reserved.