Epilepsy and argininosuccinic aciduria

We have reviewed the occurrence of epilepsy in our patients with argininosuccinic aciduria (ASA) (OMIM 207900) and the possible relationship of late epilepsy to symptomatic seizures in the neonatal period, hyperammonaemia and treatments.

We retrospectively analysed 11 ASA patients (8 neonatal onset and 3 late onset), 6 of whom had developed epilepsy.

Epilepsy in our sample was frequent (55 %). It developed after a seizure-free period from the onset of the metabolic disease and seizures were responsive to treatment in all cases. Arginine plasma levels were kept in the same range for the 2 groups of patients with and without epilepsy.

Although epilepsy is reported to be common among patients with ASA, very few long-term follow-up studies are available. The pathophysiological mechanism of epileptogenesis remains unclear. Neither hyperammonaemia nor acute symptomatic seizures at birth seem to be predictive of late epilepsy. Excessive arginine dosages as a cause of epilepsy could be reasonably excluded since our 3 late onset patients developed epilepsy before the diagnosis of ASA, at a time when they were likely to be arginine deficient. Arginine deficiency may not be excluded as cause of epilepsy, but further studies are needed to define its role.