Changes in the pattern reversal visual evoked potentials in myasthenia gravis.

To investigate the possibility of impaired cholinergic transmission in the Central Nervous System (CNS) in patients with Myasthenia Gravis (MG), the PR-VEPs in 11 newly diagnosed MG patients before and after pyridostigmine treatment compared to those recorded from 10 normal subjects tested in two different occasions one month apart. All patients, (7 female and 4 male) had a good response to treatment. The amplitude of the P100 of the PR-VEPs of the MG patients before and after treatment was significantly lower than those recorded from the normal control subjects and the latency significantly longer. In the patient group the amplitude of the P100 improved significantly after treatment. These results provide neurophysiological evidence of impaired cholinergic transmission in the CNS in patients with MG and suggest that PR-VEPs offer an easily applicable non-invasive method to study the central effects of MG and possibly a procedure to monitor the effectiveness of pyridostigmine treatment.