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Myasthenic crisis — SCE Neurology MCQ

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EasyNeuromuscularMyasthenic crisisSCE Neurology

A 31-year-old woman presented with known myasthenia with increasing dysphagia and breathlessness after infection. On examination, single-breath count was low and neck flexion was weak. Initial investigations showed: FVC was falling and arterial blood gas showed rising carbon dioxide. What is the most likely underlying mechanism?

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Correct answer: C — failure of neuromuscular transmission

failure of neuromuscular transmission is the best answer because the vignette describes Myasthenic crisis: bulbar and respiratory weakness in MG is myasthenic crisis requiring urgent ventilatory planning. Small-vessel lipohyalinosis is plausible in a neighbouring presentation, but the chronology, examination or investigation pattern does not match the key discriminator here. JC virus infection of oligodendrocytes and Alpha-synuclein neurodegeneration are less appropriate because they would require different localisation, timing or test findings; Functional abnormality of motor prediction networks would fit a different syndrome. Clinical pearl: increasing pyridostigmine alone is insufficient and may worsen secretions.

Reference: NICE NG42; ABN myasthenia gravis guidance; EAN/PNS GBS-CIDP guidance