Pyridoxine dependent seizures

Lead investigator

Dr P Baxter

About the study

This study was conducted from October 1995 to October 1997. During this time, Pyridoxine dependency was a rare, but treatable, recessively inherited cause of seizures starting in early childhood.

Since its description in 1954, fewer than 50 definite cases have been described in the published literature, all in case reports or small hospital-based series. No large-scale or population-based study had ever been reported and the incidence and prevalence of the condition were essentially unknown.

Up to one-third of reported cases presented atypically with, for example, an onset of convulsions after the neonatal period (up to two years) or a transient response to standard anticonvulsants.

Other clinical complications occurred, such as abdominal symptoms, early visual agnosia, structural changes in the nervous system, or seizures provoked by intercurrent infections, but their frequency was unknown. With these varied presentations, the condition was likely to be under recognised.

The outcome for psychomotor development was reputed to be poor even in cases treated early, but this was debatable as no formal study had taken place. The reported required dose of pyridoxine for individual patients varied between 10 and 1000 mg daily, but it was not changed with age, and the optimal dose was unknown. Individual case reports suggest a disorder of GABA metabolism was at fault, but neither the metabolic nor the genetic abnormality was identified.

This study aimed to:

1. Determine the prevalence of definite or possible pyridoxine-dependent seizures in children under 16 years of age.
2. Prospectively study the incidence in children under five years of age.
3. Define the clinical presentation, natural history, and clinical management of pyridoxine dependency.

Duration

October 1995 – October 1997

Published papers

Support Group

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