Uhthoff’s Phenomenon
Uhthoff phenomenon, which can be used synonymously with Uhthoff’s symptoms describes transient temperature-dependent or loss of vision. Conduction stops in any nerve if the temperature gets too high. In a damaged nerve, e.g., by demyelination, this shutdown temperature is lowered, and may approach normal body temperature. Transient neurological dysfunction may then appear with a hot shower, exercise, or fever[i]. Uhthoff’s symptom is particularly associated with a transient loss of vision with optic neuritis[ii]. Due to the correlation of optic neuritis and multiple sclerosis- Uhthoff’s symptom is most commonly known as a feature of multiple sclerosis.
It was discovered and named after Wilheim Uhthoff[iii] (July 31, 1853 - March 21, 1927), a German opthalmologist. He began his studies in 1873, attending the universities of Tübingen, Göttingen, Rostock, and Berlin. He received his doctorate at the latter in 1877 and was licensed in 1878. He turned to eye medicine and became an assistant to Heinrich Leopold Schoeler (1844-1918). He was habilitated at Berlin in 1884, and in 1890 followed a call to Marburg as ordentlicher Professor, succeeding Hermann Schmidt-Rimpler (1838-1915). In 1896 he succeeded Carl Friedrich Richard Förster (1825-1902) at Breslau, remaining in this tenure until he was emerited in 1923. Uhthoff’s most important work concerns studies on the relationship between general diseases, particularly those of central nervous system and poisonings, to ophthalmology.
The cause of Uhthoff’s symptom is unknown. There are many theories in circulation including heat causes a blockade of partially demyelinated axons. Other theories suggest that heat itself, effects of serum calcium, blockade of ion channels, circulatory changes, and unidentified blood serum substances. One study determined that the cause was a metabolic byproduct of exercise or increases in body temperature causing a reversible conduction block in demyelinated optic...