Demyelinating Diseases USMLE Step 1 Practice Question
A 67-year-old man with a history of terminal ileal resection presents with progressive numbness in his feet and gait instability over 3 months. Vital signs: BP 138/82, HR 88, RR 16, Temp 37°C, SpO2 98%. Examination reveals decreased vibration sense in both feet and bilateral Babinski signs. Serum vitamin B12 level is 185 pg/mL. Cranial nerves are intact. Which of the following is the most likely diagnosis?
Answer choices
- ATransverse myelitis
- BSubacute combined degenerationCorrect answer
- CGuillain Barré syndrome
- DAmyotrophic lateral sclerosis
- EMultiple sclerosis
- FCopper deficiency myelopathy from excessive zinc supplementation
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