Optic nerve causing optic neuritis

A 28-year-old obese, female presents today with complaints for several weeks of vision problems (blurry) and difficulty with concentration and focus. She is an administrative para-legal for a law firm and notes her symptoms have become worse over the course of the addition of more attorneys and demands for work.

Today, she noticed that her symptoms were worse and were accompanied by some fine tremors in her hands. She has been having difficulty concentrating and has difficulty voiding. She went to the optometrist who recommended reading glasses with a small prism to correct double vision. She admits to some weaknesses as well. No other complaints of fevers, chills, URI, or UTI

PMH: non-contributory
PE: CN-IV palsy. The fundoscopic exam reveals edema of the right optic nerve causing optic neuritis. Positive nystagmus on positional maneuvers. There are left visual field deficits. There was short-term memory loss with a listing of familiar objects.

DIAGNOSIS: multiple sclerosis (MS).

Question:

Describe what is MS and how did it cause the above patient’s symptoms?