Wilhelm Uhthoff (1853-1927) a German neuro-ophthalmologist described an optic neuritis patient in 1890 who would develop episodes of temporary vision loss during physical exercise.
This condition, subsequently known as Uhthoff’s phenomenon, was later found to be caused by a rise in body temperature.
More than half of all multiple sclerosis (MS) patients spontaneously report being sensitive to environmental heat.
When specifically asked, as many as 70% MS patients report that high temperatures worsened their MS.
Increased temperature blocks action potentials in compromised (demyelinated) neurons resulting in slower conduction velocities and/or temporary failure of conduction altogether (conduction block).
This explains the temporary exacerbations in neurologic dysfunction that underlie Uhthoff’s phenomenon.
So what can you do?
Drugs like Ampyra (dalfampridine or 4-aminopyridine) improve conduction across demyelinated neurons, and can improve Uhthoff’s phenomenon, but these drugs are not currently FDA approved for this indication, and used off label can cost as much as $1200/month. It might be cheaper to move to Alaska or buy a window box AC unit?