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?
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Oligodendrocytes, the myelin-producing cells of the CNS- Which type of hypersensitivity reaction underlies multiple sclerosis?
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Type IV (T-cell mediated) hypersensitivity- What are the three components of Charcot's classic neurologic triad, historically associated with MS?
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Nystagmus, intention tremor, and scanning (staccato) speech- What is the most common initial presenting symptom of multiple sclerosis?
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Optic neuritis, unilateral vision loss with pain on eye movement- Where are demyelinating plaques classically located on MRI in multiple sclerosis?
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Periventricular white matter- What CSF finding supports a diagnosis of multiple sclerosis?
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Oligoclonal IgG bands present in CSF but not in a matched serum sample- What demographic is most commonly affected by multiple sclerosis?
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Young women, typically between ages 20 and 40- What is internuclear ophthalmoplegia, a classic MS eye finding?
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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?
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Temporary worsening of symptoms with increased body temperature, such as a hot shower or exercise- What is Lhermitte sign?
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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?
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Relapsing-remitting- What is the first-line treatment for an acute multiple sclerosis relapse?
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High-dose intravenous corticosteroids- What is the target antigen of autoantibodies in myasthenia gravis?
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Postsynaptic nicotinic acetylcholine receptors at the neuromuscular junction- Which type of hypersensitivity reaction is myasthenia gravis?
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Type II hypersensitivity- What is the hallmark pattern of muscle weakness in myasthenia gravis?
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Fatigable weakness that worsens with repeated activity and improves with rest
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