skip to main content

Myasthenia gravis electrophysiology — SCE Neurology MCQ

Instant feedback + full explanation. One question, done properly.

HardNeurophysiologyMyasthenia gravis electrophysiologySCE Neurology

A patient has fluctuating ptosis and diplopia that worsen late in the day. AChR and MuSK antibodies are negative, repetitive nerve stimulation is normal, MRI orbits is unrevealing and examination still strongly suggests ocular myasthenia. Which test has the greatest diagnostic sensitivity now?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Single-fibre EMG of a symptomatic facial muscle

The best answer is “Single-fibre EMG of a symptomatic facial muscle”. Single-fibre EMG detects increased jitter and blocking and is the most sensitive neurophysiological test when antibody testing and routine repetitive stimulation are unrevealing in suspected ocular myasthenia. “Sural-nerve biopsy for a length-dependent neuropathy” is less appropriate because peripheral sensory-nerve tissue does not assess the neuromuscular junction “Visual-evoked potentials as a test of neuromuscular transmission” is less appropriate because visual-evoked potentials assess afferent optic pathways rather than fatigable extraocular weakness “Dopamine-transporter SPECT for fatigable ptosis” is less appropriate because dopaminergic imaging has no role in this junctional phenotype “Lumbar puncture for isolated oligoclonal bands” is less appropriate because CSF oligoclonal bands do not establish impaired neuromuscular transmission

Reference: Neuromuscular junction disorders: mimics and chameleons. https://pn.bmj.com/content/24/6/467