Refractory focal epilepsy in a patient with methylmalonic aciduria: case report on positive and long-lasting effect of rufinamide.

We report on a 5-year-old boy with methylmalonic aciduria, an autosomal recessive inborn error of metabolism leading to accumulation of methylmalonic-CoA and thereby causing intoxication with leading symptoms of hyperammonaemia and metabolic acidosis. Hyperammonemia itself causes brain oedema. In our patient, this led to a vast metabolic stroke of the left hemisphere and subsequent pharmacoresistant epilepsy. Guided by his main seizures--drop attacks--the orphan drug rufinamide (RUF) was introduced as "off-label use" and led to freedom of drop attacks and tonic-clonic seizures over a period of 14 months as well as normalisation of the electroencephalogramm. Only once during an episode of fever and diarrhoea with reduced level of RUF did some provoked seizures with focal complex semiology for the time period of infection occur. In the 16 months follow-up, the patient also improved in his development, showing a more stable gait with the hemiparesis and understanding more complex sentences.