Peripheral Neuroanatomy, Human Anatomy, USMLE Step 1 - Full Vignette with Extended Explanations

A 30-year-old woman with several months of recurrent painless focal neuropathies-including transient foot and wrist drops, intermittent finger numbness, and nocturnal hand paresthesias-develops gradual hand clumsiness. Family members experienced early nerve entrapment syndromes. Electrodiagnostics reveal demyelinating features, especially at compression sites, and imaging is unremarkable for systemic causes. What underlying mechanism should be considered, and which clinical findings help distinguish this pattern from other neuropathies?

VIDEO INFO
Category: Peripheral Neuroanatomy, Human Anatomy, USMLE Step 1
Difficulty: Hard - Advanced level - Challenges experienced practitioners
Question Type: Management - Clinical management decisions
Case Type: Rare Presentation

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QUESTION
A 30-year-old woman presents for evaluation of recurrent focal neuropathies. Over 18 months she has experienced: transient right foot drop after an evening seated with legs crossed; transient left wrist drop after sleeping on her arm during a red-eye flight from Asia; intermittent numbness of the right ring and small fingers when cycling; and nocturnal paresthesias in the radial three digits bilaterally....

OPTIONS
A. Institute pressure-avoidance counseling and task-specific splinting (neutral wrist splints at night and during provocative tasks; nighttime elbow extension splint on the right), order targeted PMP22 copy-number analysis (deletion/duplication by MLPA or equivalent) with genetics referral, and trea...
B. Adopt the same conservative program but add immediate prophylactic decompressions at all symptomatic entrapment sites in a single session and defer PMP22 testing in favor of later whole-exome sequencing, because early multilevel surgery prevents further demyelination regardless of genetic etiology.
C. Treat as immune-mediated multifocal demyelinating neuropathy and begin high-dose immunotherapy now (prednisone 1 mg/kg/day with a taper plus IVIG 2 g/kg over 2-5 days), postpone genetic testing, and arrange nerve biopsy if relapses occur despite therapy.
D. Start lifelong warfarin anticoagulation for antiphospholipid antibody positivity to prevent recurrent mononeuropathies and avoid splints and genetic testing, because ischemic microinfarcts are the most likely mechanism in this setting.

CORRECT ANSWER
A. Institute pressure-avoidance counseling and task-specific splinting (neutral wrist splints at night and during provocative tasks; nighttime elbow extension splint on the right), order targeted PMP22 copy-number analysis (deletion/duplication by MLPA or equivalent) with genetics referral, and treat symptoms with a neuropathic agent as needed (e.g., duloxetine 30-60 mg/day or pregabalin 50-75 mg at night), reserving focal decompression only for fixed deficits persisting after strict conservative care.

EXPLANATION
Institute pressure-avoidance counseling and task-specific splinting (neutral wrist splints at night and during provocative tasks; nighttime elbow extension splint on the right), order targeted PMP22 copy-number analysis (deletion/duplication by MLPA or equivalent) with genetics referral, and treat symptoms with a neuropathic agent as needed (e.g., duloxetine 30-60 mg/day or pregabalin 50-75 mg at night), reserving focal decompression only for fixed deficits persisting after strict conservative care. This is correct because the history of recurrent painless mononeuropathies at compression-prone sites, fa...


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