Uhthoff's sign

A transient worsening of pre-existing neurological deficits (vision loss, fatigue, weakness, or numbness) triggered by an increase in core body temperature, resulting from heat-sensitive conduction block in demyelinated nerve fibers.

Causes

• Multiple sclerosis (classic association)

• Neuromyelitis optica spectrum disorder (less commonly)

• Heat-related triggers

  • Exercise

  • Infection

  • Fever

  • Hot showers or baths

  • Environmental heat

  • Sauna

  • Emotional stress

  • Pregnancy or hormonal heat intolerance