Uhthoff's symptom in optic neuritis: relationship to magnetic resonance imaging and development of multiple sclerosis.

Eighty-one patients with a first attack of isolated optic neuritis, 40 with Uhthoff's symptom (Group 1) and 41 without (Group 2), were studied. All had a neurovisual examination, 74 of 81 patients had the pattern visual evoked potential recorded at rest, and 43 had magnetic resonance imaging brain scans. The pattern visual evoked potential P100 latency was prolonged, Group 1 with a mean of 136 +/- 19 msec. Group 2 with a mean of 131 +/- 19 msec (control subjects, 102 +/- 5 msec; n = 84), and the P100 amplitude was reduced, without significant difference between the groups. Abnormal magnetic resonance imaging scans were present in significantly more patients in Group 1 (p less than 0.025). Treatment of optic neuritis with corticosteroids had no effect on the evolution or duration of Uhthoff's symptom. Overall, 35 of 81 (43%) patients, followed for a mean of 3.5 years, developed multiple sclerosis. The incidence was significantly greater in Group 1 (p less than 0.01). Uhthoff's symptom also correlated with a higher incidence of recurrent optic neuritis. We conclude that Uhthoff's symptom is a prognostic indicator for the early development of multiple sclerosis.