Case history

A 13-year-old girl, with a background of stage 4 thoracic neuroblastoma (diagnosed 2003) and residual spastic paraplegia with neuropathic bladder and irregular bowel habit, presented with increasing muscle fatigue and decreased exercise ability over the past 6 months. She reported symptoms including periodic slurring of speech, difficulty swallowing and the inability to smile or blink. These episodes were reported to last between 10 and 90 min. She also presented with ongoing nausea and a reduced appetite.

On inspection, she had an indistinct smile and loss of the left nasolabial fold. Examination of the cranial nerves elucidated a bilateral facial weakness, decrease palate movement and bilateral reduced corneal reflexes. She had normal eye movements, no ptosis and her pupils were equal and reactive to light. Neurological examination of the upper limbs demonstrated weakness in C4–5 but otherwise she had normal power in her arms and hands. Tone, reflexes, coordination and sensation were normal.

In light of her …