Uhthoff's symptom is a condition most commonly observed multiple sclerosis and particularly in Optic Neuritis where small increases in body temperature (hyperthermia) caused by exercise, hot baths or showers or otherwise, cause a worsening of symptoms.

The Uhthoff induced symptoms tend to go away as the body returns to its correct temperature after anything from several minutes to a few hours has passed. A very few cases have been reported where new symptoms have been induced by hyperthermia that have not eased away as the hyperthermia passes.

In one study, patients presenting with Optic Neuritis with associated Uhthoff's symptom were found to be more likely to convert to multiple sclerosis than those presenting with Optic Neuritis without any associated Uhthoff's symptom [McDonald WI and Sears TA, 1970].

One explanation of Uhthoff's symptom is that hyperthermia induces a heat-linked neuro-blockade of partially demyelinated axons. Other theories suggest that heat itself, effects of serum calcium, blockade of ion channels, circulatory changes, heat shock proteins and unidentified humoral substances.
 
 

Factors provoking Uhthoff's symptom [Scholl et al, 1991]

Factor	No. of Patients	Per cent %
Physical exertion	21	52.5
Hot bath or shower	11	27.5
Hot weather	11	27.5
Stress, anxiety, anger	5	12.5
Tired, end of day	4	10.0
Hot food or drink	3	7.5
Cooking	2	5.0
Other	3	7.5

See Optic Neuritis

Uhthoff's Symptom Links
Uhthoff and his symptom
Influence of temperature changes on multiple sclerosis
Uhthoff's symptom in optic neuritis
MSCenter - The Effects of Heat on MS

MS Glossary
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