A 59-year-old woman presented following a transient episode of confusion. She had temporal lobe epilepsy, well controlled on sodium valproate; she had been seizure free for 14 years. She had hypertension and had a history of a subarachnoid haemorrhage 14 years before. There was no family history of epilepsy or neurological disorders, and no history of pregnancy issues or birth difficulties, childhood seizures or febrile convulsions.

She had presented with a single brief and sudden onset episode of confusion, which resolved over several minutes without loss of consciousness. Unfortunately, there was no witness account. The episode differed from her previous seizures, which had comprised visual disturbance, euphoria, speech arrest and subsequent confusion, without automatisms or secondary generalisation. These were classifiable as focal dyscognitive seizures. Her medication adherence was good and there was no history of alcohol excess. Her neurological examination was normal and her routine blood tests, ECG and MR scan of brain were normal.

Four months later, she re-presented with several further episodes of transient confusion. An eyewitness account from a relative described them as “identical to her previous seizures”. There were also several occasions where she had awoken on the floor with no recollection of how she got there, finding herself confused on waking and having been incontinent of urine. Neurological examination was again normal.

What are the potential causes for these episodes and how should they be investigated and managed?

People with epilepsy who have an initial good response to antiepileptic drugs (AEDs) are likely to remain seizure free in the long term.1 Further events despite optimal AED therapy should prompt careful reassessment. Leach has proposed the following key questions1 (box 1). In a patient with previously …