Demyelinating disorders: Pathology review

At the neurology department, a 23 year old male, named Charles, is brought by his parents because of weakness in his feet that started 2 days ago and worsened over time. During clinical examination, the deep tendon reflexes in his lower extremities are decreased but sensation is intact. Past medical history reveals a case of gastroenteritis about three weeks ago. Next to Charles, there’s a 26 year old female, named Maria, that came in because of an episode of blurring in her left eye and pain during eye movement. She had a similar episode a few months ago that lasted about a week and resolved without any treatment. She also describes an episode where she felt an electric shock-like sensation through her body after having a hot shower.

Alright, so both of them have a demyelinating disorder. This occurs when myelin, the protective sheath that surrounds the axons of neurons, is destroyed. Now, myelin is produced by oligodendrocytes in the central nervous system, or CNS, which includes the brain and the spinal cord, while in the peripheral nervous system, or PNS, which includes all of the neurons that extend beyond the brain and the spinal cord, it is produced by Schwann cells. Myelin helps the neurons to quickly send electrical impulses. As a result, the destruction of myelin, or demyelination, makes communication between neurons difficult, ultimately leading to all sorts of sensory, motor, and cognitive problems. Okay, now demyelinating disorders can be classified into two groups. The first one includes disorders that affect the myelin in the CNS, such as multiple sclerosis, acute disseminated encephalomyelitis, progressive multifocal encephalopathy and central pontine myelinolysis. The second group includes diseases that affect the myelin in the PNS, like Guillain-Barre syndrome and Charcot-Marie-Tooth. Now, other less high yield demyelinating disorders include Krabbe disease, metachromatic leukodystrophy and adrenoleukodystrophy.