Lack of Visual Habituation in Multiple Sclerosis: An Electrophysiological Study

In this study, we aimed to investigate habituation of pattern-reversal visually evoked potentials (VEPs) in patients with relapsing remitting (RR) multiple sclerosis (MS). Twenty-one patients with this diagnosis and with a history of optic neuritis (ON), 29 such patients without a history of ON, and 25 normal controls were enrolled to study. One eye of each patient in the group with a history of ON and one eye of each subject in the control group was randomly selected. In the group with a past history of ON, the affected eye of the patients was selected in unilateral cases and the eye in which showed the greater latency delay of the P100 component in bilateral cases. P100 amplitudes were determined by visual inspection in 10 blocks of 512 responses and habituation was analysed as the percentage amplitude change between the 1st and 2nd-10th blocks. Amplitude of the P100 component of the VEP showed a significant clear-cut habituation after the first block in the control group but neither patient group showed a significant decrease in P100 amplitude. We conclude that our electrophysiological study has shown a lack of habituation in patients suffering from RR MS. This result could be important for the evaluation of visual system involvement in patients with MS, with or without a previous history of ON.