Neurological Deficits Following the Hot Bath Test in Multiple Sclerosis

To the Editor.— In their article entitled "Persistent Neurological Deficit Precipitated by Hot Bath Test in Multiple Sclerosis," Berger and Sheremata1conclude that hyperthermia can provoke an exacerbation in multiple sclerosis (MS). This is in contradistinction to the well-known reversible worsening of signs and symptoms in MS induced by hyperthermia, which is the result of a reversible block of impulse conduction caused by a critical decrease in action current available for conduction.2,3 We have never observed persistent neurological deficits in more than 20 years' experience with the hot bath test; however, unlike Berger and Sheremata, we have rarely studied patients already in an exacerbation, and then only in a single experimental protocol.4I don't believe the authors have demonstrated what they conclude. They have, I believe, shown that in patients already in acute exacerbation, hyperthermia effects on signs and symptoms may not always reverse. The mechanism, however,