Demyelinating disorders: Pathology review

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Demyelinating disorders: Pathology review


Autonomic nervous system disorders

Horner syndrome

Orthostatic hypotension


Demyelinating disorders: Pathology review

USMLE® Step 1 questions

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USMLE® Step 1 style questions USMLE

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A 19-year-old football player is brought to the emergency department by his roommate after he complained of lower extremity weakness. He initially had “tingling” of the toes, but he attributed it to an “intense practice” several days ago. The patient also reports he has not voided urine in the last 5 days. Four weeks ago, the patient had a febrile diarrheal illness that resolved after several days. Temperature is 37.0°C (98.6°F), pulse is 44/min, respirations are 14/min, and blood pressure is 128/74 mmHg. Physical examination reveals absent ankle and knee reflexes but intact sensation to light touch and pain. A lumbar puncture is performed. Which of the following cerebrospinal fluid findings is most likely to be seen in this patient?  


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.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Adams and Victor's Principles of Neurology 11th Edition" McGraw-Hill Education / Medical (2019)
  4. "Multiple Sclerosis and Demyelinating Diseases" Lippincott Williams & Wilkins (2006)
  5. "Multiple sclerosis is primarily a neurodegenerative disease" Journal of Neural Transmission (2013)
  6. "Acute disseminated encephalomyelitis" Seminars in Pediatric Infectious Diseases (2003)

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