My thoughts are for our readers with MS who are having to live through and cope with the latest heatwave. The BBC has just reported that this is the hottest late August bank holiday on record; “Temperatures had reached 33.2C (91.8F) at Heathrow by 14:16 BST, the Met Office said, beating the previous record of 28.2C set two years ago. On Sunday, the record for the hottest late August Bank Holiday weekend was broken, with a high of 33.3C”.
How are you tolerating the heat? I suspect many of you with heat sensitivity will be experiencing worsening fatigue, pseudo-relapses (heat-induced intermittent symptoms) and difficulty sleeping. Are you coping? Do you have any advice for your fellow MSers?
Please note that the main consequences of a raised body temperature in demyelinated, or remyelinated, pathways is slowed conduction. The commonest example is exercise-induced fatigue, but this summer’s heatwave will be causing symptoms without the need for exercise. Some of you will find difficulty walking difficult; your legs will begin to drag minutes into walking rather than after 20-30 minutes. Others will notice blurring of vision mid-morning when in the past this would only happen in the late afternoon. The reason for this is that the demyelinated segments in the nerve stop conducting due to conduction block induced by a slight rise in temperature affecting the functioning of the sodium channels. The latter are the molecules in the membranes of nerve cells that transmit the electrical signal down a nerve fibre, which require energy to work. These sodium channels are ion pumps, which are optimised to function at a certain temperature and explains why MSers are heat sensitive.
Most of you will have heard of Uhthoff’s phenomenon. Wilhelm Uhthoff (1853-1927) was a famous German Professor of ophthalmology who described temporary visual loss associated with optic neuritis linked to physical exercise. This was later found to be caused by a rise in body temperature. This phenomenon is now known to affect other neurological systems as well; for example, the motor system when walking, balance and sensory pathways and even the cognitive centres.
Apart from cooling, we do not had a treatment for Uhthoff’s phenomenon. The drug Fampridine has been licensed to improve walking speed in MSers. Interestingly, several MSers have said to me in the past that their heat sensitivity has improved since taking Fampridine.