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Non-Fatigable Ptosis – Myogenic Differential — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularNon-Fatigable Ptosis – Myogenic DifferentialSCE Neurology

A 50-year-old man presents with unilateral ptosis that varies throughout the day. He has no diplopia. Ice pack test is negative. Examination shows fixed ptosis of 4 mm that does not improve with rest. There is no lid twitch. AChR and MuSK antibodies are negative. CK is normal. CT chest shows no thymoma. What should be considered?

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Correct answer: B — Myogenic ptosis — consider CPEO, myotonic dystrophy, or oculopharyngeal muscular dystrophy

Fixed, non-fatigable ptosis with a negative ice pack test and negative MG antibodies should prompt consideration of myogenic causes (CPEO — mitochondrial; myotonic dystrophy — DMPK mutation; OPMD — PABPN1 mutation), aponeurotic ptosis (involutional — common in the elderly), or neurogenic causes (CN III palsy, Horner syndrome). Myogenic ptosis tends to be bilateral and progressive. CK may be normal in some myopathies. Muscle biopsy and genetic testing may be needed. A: MG antibody retesting may be considered but the fixed, non-fatigable pattern argues against it. C: Horner syndrome has miosis and is typically <2 mm ptosis. D: Aponeurotic ptosis is common in older adults but at 50, myogenic causes should be excluded. E: Not all ptosis is MG.

Reference: ABN Neuromuscular Guidelines; ABN Neuro-ophthalmology Guidelines