Case presentation

An 18-year-old woman was admitted with recurrent seizures. These began focally in the left leg and rapidly generalised. She had complained of a mild generalised headache for the preceding 4 weeks, associated with rainbow-coloured lights in her central vision. On admission, she reported formed visual hallucinations, which included animals and vehicles. She had been previously well, she drank little alcohol, did not smoke, took only an oral contraceptive pill and had no significant family history.

On examination, she was apyrexial. There was continuous myoclonic jerking of the left arm and neck, left homonymous hemianopia, left hemiataxia and left hemisensory loss.

The myoclonus continued despite aggressive antiepileptic treatment with sodium valproate, levetiracetam and clobazam. She was intubated in a thiopentone-induced coma for 24 h.

Investigations included normal routine haematology, biochemistry, haematinics and serum lactate dehydrogenase; tests for diabetes mellitus, pregnancy, syphilis and HIV were negative. CT scan of the head showed a right occipital hypodense area, reported as a possible infarct (figure 1A). A CT cerebral venogram was normal. MR scan of the brain showed right occipital and parietal cortical foci of T2 hyperintensity with gyral swelling (figure 1B, C). There was no contrast enhancement or restricted diffusion. Cerebrospinal fluid (CSF) protein was 1.04 g/L (normal ≤0.4) and CSF lactate was 2.5 mmol/L (normal ≤3). The opening pressure, cell count, cytology, glucose, oligoclonal bands, lactate dehydrogenase, viral PCR and cultures were normal or negative. Electroencephalogram (EEG) showed continuous right posterior spike-and-wave activity. MR angiography showed no vertebral artery dissection. Transthoracic echocardiogram was normal. Peripheral neurophysiology showed an axonal sensorimotor neuropathy and myopathic changes.