How does demyelinating disease affect the brain stem?
Multiple sclerosis often results in demyelination of the fast-conducting, heavily myelinated nerve fibers traveling along the brain stem.
These include the cerebellar–vestibular pathways, medial longitudinal fasciculus, and pyramidal pathways.
Bilateral INO is almost pathognomonic of multiple sclerosis.
Another hallmark of brain stem multiple sclerosis is the combination of bilateral cerebellar and pyramidal signs producing ataxia and pathologically brisk reflexes.