Serial Pattern Shift Visual Evoked Potentials in Multiple Sclerosis

Abstract

Forty patients with MS initially tested in our laboratory were recalled for repeat PSVEP testing approximately two years later. Twelve normal controls were tested in a similar manner approximately two years apart. The PSVEP positive peak latency changed little in the 24 control eyes (mean 1.4 msec, range 0-6) over the study interval. Most MS patient eyes also showed little change in PSVEP latency over the two year study interval. Fifty-eight eyes changed 8 msec or less. Eighteen eyes showed a PSVEP latency increase of 10 msec or more. Six of these eighteen eyes were symptomatic (attack of clinical optic neuritis), twelve asymptomatic during the study interval. Symptomatic eyes tended to have greater latency increases during the study interval than asymptomatic eyes.Significant latency increases occurred with equal frequency in previously normal eyes (normal PSVEP on first test) and abnormal eyes (abnormal PSVEP on first test or previous clinical optic neuritis). Significant latency increases occurred with greater frequency in patients with a mixed or progressive course than in patients with a remitting-relapsing course, and in patients with greater disability ratings (Kurtzke 3-7) than in patients with lower disability ratings (Kurtzke 0-2). Bilateral latency increases occurred during the study interval more frequently than expected by chance. Patient age and disease duration did not significantly influence the number of PSVEP latency increases seen during the study interval.Four eyes decreased in latency by 10 msec or more during the study interval. All these eyes had had an episode of acute optic neuritis which began in the 5 weeks immediately preceding the 1st PSVEP test.In our MS patients, 13% of eyes per year developed latency increases of 10 msec or more. These may represent new demyelinating lesions. If so, one-third of these lesions were clincally symptomatic.