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.