Epidemiology of pyridoxine dependent and pyridoxine responsive seizures in the UK.

OBJECTIVE To study the epidemiology of pyridoxine dependent seizures and other forms of pyridoxine responsive seizures. DESIGN Monthly notifications to the British Paediatric Surveillance Unit over two years. Questionnaire follow up. SETTING UK and the Republic of Ireland. PATIENTS Children aged 15 years or younger whose seizures respond to pyridoxine. INTERVENTIONS None. MAIN OUTCOME MEASURES Numbers of children with definite, probable, and possible pyridoxine dependent seizures or other seizures responsive to pyridoxine. RESULTS Point prevalence and birth incidence: 1/687 000 and 1/783 000, respectively (definite and probable cases); 1/317 000 and 1/157 000, respectively (all types of pyridoxine responsiveness). NOTIFICATIONS: Pyridoxine dependency: 14 definite, 9 probable, and 10 possible cases; neonatal seizures not meeting case definitions: 7; infantile spasms: 5. Eight of 18 families of definite/probable cases had 2 affected siblings. Just over a third had atypical presentations and just under a third had features and/or initial diagnoses of birth asphyxia and neonatal hypoxic ischaemic encephalopathy. CONCLUSIONS Pyridoxine dependency is rare. Atypical presentations are relatively frequent. A trial of pyridoxine is justified in all cases of early onset intractable seizures or status epilepticus, whatever the suspected cause.