As the heat rages on, patients with multiple sclerosis (MS) are left worse for wear as hotter temperatures may be worsening their symptoms, particular when it comes to thinking and memory problems. Numbness, limb weakness, and problems with balance and vision are among the most widely known symptoms of the disease, but problems with thinking and memory are also very common.

Researchers had tested the memories and information processing abilities of MS patients and people without the disease at different points during the year. They found that when exposed to the heat during warmer seasons, the MS patients performed worse on the cognitive tests. No seasonal difference was seen in test performance among people without multiple sclerosis:
Neurologist Barbara Giesser, MD, says the link between hot weather and worsening MS symptoms has been recognized for more than 100 years.

"At the turn of the 20th century, long before we had MRIs and fancy diagnostics, one way of diagnosing MS was the 'hot bath' test," she says. "They would put the patient in a tub of very hot water and if their symptoms worsened, the diagnosis was confirmed."

A brain imaging study published last summer by researchers at Harvard University showed that MS-associated brain lesions actually occur more often in warmer months than in colder ones.

Heat appears to slow down nerve impulses that are already impaired by the disease, Giesser says.

"Basically nerves are electrical cables," she says. "MS damages the insulation and short circuits the nerves so that they don't conduct signals as efficiently. If you heat up a damaged nerve, that causes further problems."
The study was presented Thursday at the 63rd annual meeting of the American Academy of Neurology in Honolulu.

via WebMD