This accumulation of microscopic lesions to the point that it achieves macroscopic expression in the organism is a metaphor for something. I can't think for what right now. All I know is that it jumps some barrier, like quantitative to qualitative, across levels of meaning. A metaphor for metaphor perhaps.

People with progressive MS will notice cognitive changes. Loss of short-term memory, inability to find the right word or name on command, increasing difficulty absorbing new information, disorientation in space and time. Cognitive scars. Multiple cognitive scars. Tremors in extremities become increasingly noticeable and problematic. The feet or legs may display clonus and the entire body shows hyper-reflex reactions. Hitting the knee can produce an involuntarily powerful reflex kick. Placing a sharp object at the soft point of the sole of the foot can send the leg into uncontrollable rhythmic spasms. Muscles cramp and fatigue easily. The motivation to sustain long exposition and the kind of planning required to support a complex narrative decline. Synonyms disappear with the subsidence of the available lexicon.

Ironically, another symptom of multiple sclerosis is a form of vertigo, known as acute labyrinthitis.