Multiple sclerosis, myasthenia gravis, and Guillain-Barre syndrome mechanisms and distinguishing features tested on USMLE Step 1.
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- What type of cell does multiple sclerosis primarily destroy?
- Oligodendrocytes, the myelin-producing cells of the CNS
- Which type of hypersensitivity reaction underlies multiple sclerosis?
- Type IV (T-cell mediated) hypersensitivity
- What are the three components of Charcot's classic neurologic triad, historically associated with MS?
- Nystagmus, intention tremor, and scanning (staccato) speech
- What is the most common initial presenting symptom of multiple sclerosis?
- Optic neuritis, unilateral vision loss with pain on eye movement
- Where are demyelinating plaques classically located on MRI in multiple sclerosis?
- Periventricular white matter
- What CSF finding supports a diagnosis of multiple sclerosis?
- Oligoclonal IgG bands present in CSF but not in a matched serum sample
- What demographic is most commonly affected by multiple sclerosis?
- Young women, typically between ages 20 and 40
- What is internuclear ophthalmoplegia, a classic MS eye finding?
- Impaired adduction of one eye with nystagmus of the abducting eye, caused by a medial longitudinal fasciculus lesion
- What is Uhthoff phenomenon in multiple sclerosis?
- Temporary worsening of symptoms with increased body temperature, such as a hot shower or exercise
- What is Lhermitte sign?
- An electric shock-like sensation down the spine or limbs triggered by neck flexion
- What is the most common clinical course of multiple sclerosis at the time of diagnosis?
- Relapsing-remitting
- What is the first-line treatment for an acute multiple sclerosis relapse?
- High-dose intravenous corticosteroids
- What is the target antigen of autoantibodies in myasthenia gravis?
- Postsynaptic nicotinic acetylcholine receptors at the neuromuscular junction
- Which type of hypersensitivity reaction is myasthenia gravis?
- Type II hypersensitivity
- What is the hallmark pattern of muscle weakness in myasthenia gravis?
- Fatigable weakness that worsens with repeated activity and improves with rest