For a half century, the hot bath test has been used as a “diagnostic test” in multiple sclerosis. The appearance of new neurological signs or aggravation of preexisting signs generally is transient, with resolution on return of body temperature to normal. These investigators observed four MSers, however, with considerable and prolonged neurological debilitation after hot bath testing. They suggest caution in the application of such testing.
“This observation has been disputed by others.”
To the Editor.— In their article entitled “Persistent Neurological Deficit Precipitated by Hot Bath Test in Multiple Sclerosis,” Berger and Sheremata1 conclude 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. 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. I 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.