[Long-lasting and isolated Uhthoff's phenomenon after effort preceding multiple sclerosis]

Abstract

Introduction: Described in 1890, Uhthoff's symptom corresponds to a transient blurred vision provoked by physical exercise or an increase of temperature. It is a frequent symptom occurring during the course of multiple sclerosis.

Patients and method: We report here four cases of patients presenting isolated Uhthoff phenomenon preceding multiple sclerosis by several years.

Results: These four patients presented transient neurological symptoms induced by intensive sporting activity for 1 to 6 years before diagnosis of multiple sclerosis. These symptoms were often visual but sometimes motor or sensorial. All symptoms appeared above a certain threshold specific to each patient, after 15 to 30minutes of intense physical exercise (bike, running or handball) and all disappeared after a few minutes to one hour rest with full recovery to baseline.

Discussion: Uhthoff's phenomenon is explained by a conduction block. It is due to axonal demyelization that provokes a reorganization of sodium channels induced by a decrease in a safety factor highly sensitive to temperature, or by release of soluble blocking substances (oxide nitric or cytokines).

Conclusion: Without being specific, this symptom is strongly suggestive of this disease. Our case reports confirm the existence of "infraclinic multiple sclerosis".