Definition: The brain stem is considered the most primitive part of the brain, as it controls the involuntary functions crucial to survival, such as breathing, digestion, heart rate and blood circulation. It also controls sexual function and physical growth. It is the part of the brain closest to the spinal cord and is comprised of the the medulla oblongata, the pons, the midbrain, and the reticular formation.
Multiple sclerosis lesions on the brain stem can cause symptoms such as vertigo, double vision (diplopia), facial pain and paralyis and ataxia (unsteady movements and coordination problems).

