| Uhthoff noted in 1890 while studying multiple sclerosis patients
that their symptoms worsened after exercise.
This was later discovered to be related to the rise of body temperature
caused by exercising and eventually led to the 'hot bath test'
in the 1950's.
This was to remain the principal diagnostic tool used to determine
whether a patient had multiple sclerosis for over thirty years,
with the practice ending in the 1980's when more accurate and safer
testing methods became available.
What Causes Uhthoff's Phenomenon?
The simple answer is that no-one knows.
There are various proposals put forward. It may be that it is a multifactorial
event.
These proposals include heat itself, effects of serum calcium,
circulatory changes, heat shock proteins, and unidentified
humoral substances or, probably the most popular, the blockade of
ion channels.
What is known, is that heat does play a significant role
in how people with multiple sclerosis feel, and can often worsen their
symptoms, sometimes quite dramatically.
While Uhthoff's phenomenon is particularly associated with a temporary
worsening of optic neuritis, fatigue and other symptoms can also be
made considerably worse in some patients.
To avoid, or at least, minimize the effects of heat, many
people with multiple sclerosis use a cooling vest during the summer
months.
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