Why should people with MS be concerned with heat and temperature?
Many people with multiple sclerosis (MS) are sensitive to the heat, which often increases their symptoms. The video below is Dr. Daniel Kantor, MD, Past President of the Florida Society of Neurology, discussing heat sensitivity and MS:
A rise in temperature does not affect everyone with multiple sclerosis, but for many people with MS at least some of their symptoms get worse when they get hotter. This temperature effect is sometimes described as Uhthoff's phenomenon, after Dr. Wilhelm Uhthoff, who first described it in 1890. The worsening of symptoms due to heat is widely recognized and very common. Studies have shown that nerves with damaged myelin are sensitive to changes in temperatures. Researchers note that a rise in temperature may cause a failure in the effective transmission of signals from the brain to the body (nerve conduction), and a reduction in temperature may allow more signals to be transmitted across the damaged nerve.
Symptoms may include: blurred vision after exercise, fatigue, dizziness or a weakness in one or both legs. Prolonged exposure to heat might make fatigue worse, which might in turn make other symptoms feel worse. Although this temporary worsening of symptoms (known as pseudo-exacerbation) may feel like a real MS attack, the symptoms will usually improve as the body temperature returns to normal.
Heat or exercise related symptoms may be brought on by activity, sunbathing, hot baths, emotion, exercise, fever or other things associated with an increase in body temperature. Many people with MS find hot weather difficult, but even in cooler weather, hot showers, or even daily activities like cooking in the kitchen or using a hair dryer can sometimes be a problem.
Why does temperature affect people with MS?
Heat appears to stop nerve fibers from working properly " if the fibers or their protective outer layer (myelin) have already been damaged by MS. Nerve fibers allow messages controlling different parts of the body to move around the brain and spinal cord, in the form of electrical impulses. This is known as "nerve conduction". In the brain or spinal cord, a nerve damaged by MS finds it harder to conduct these electrical impulses. Messages may get through at normal temperatures, but they are on the verge of failure. Body warming makes conduction weaker still, so some damaged nerve fibers stop working entirely, until they are cooled down. Listen to your body and take measures to cool down if you are feeling overheated.
What can be done to manage heat sensitivity?
Studies have shown that cooling the body can help lessen the negative effects of heat and improve the quality of life of people with MS.
According to a 2010 research study, Dr. George Kraft found that "...after body temperature had dropped about one degree... participants improved on tests of coordination, balance, and in the ability to sustain physical activity. We concluded that cooling is an appropriate therapy for people with MS heat sensitivity."(Kraft, George. "Rehab News: Beat the Heat!" Momentum 3.4 (2010).www.nationalmssociety.org/magazine. National Multiple Sclerosis Society. Web. July-Aug. 2010.)
"Cooling therapy is generally well-tolerated, and limited research studies have shown possible benefits for some MS-associated symptoms. The symptoms that may improve from cooling include weakness, spasticity, tremor, incoordination, walking difficulties, fatigue, visual difficulties, speech disorders, cognitive difficulty, urinary difficulties, and sexual difficulties."
(Bowling AC. Complementary and Alternative Medicine and Multiple Sclerosis. New York: Demos, 2007, pp. 76-79).