MS-4065

A 32-year-old female patient, who has a medical history of optic neuritis, visits the neurology clinic complaining of numbness and weakness in her left leg for the past few days. She mentions having experienced similar symptoms in her right arm about 7 months ago, which resolved spontaneously over a few days. Her symptoms worsen in hot weather. Upon neurological examination, weakness is observed in her left leg movements, but the rest of the examination is normal. What is the probable underlying pathophysiology of her condition?