There is increasing evidence that
vitamin B6, given either as
pyridoxine or
pyridoxal 5'-phosphate, can sometimes result in improved seizure control in idiopathic
epilepsy. Whole-exome sequencing was used to identify a de novo mutation (c.629G>A; p.Arg210His) in KCNQ2 in a 7-year-old patient whose neonatal
seizures showed a response to
pyridoxine and who had a high plasma to CSF
pyridoxal 5'-phosphate ratio, usually indicative of an inborn error of
vitamin B6 metabolism. This mutation has been described in three other patients with neonatal epileptic
encephalopathy. A review of the literature was performed to assess the effectiveness of
vitamin B6 treatment in patients with a KCNQ2
channelopathy. Twenty-three patients have been reported to have been trialled with B6; in three of which B6 treatment was used alone or in combination with other
antiepileptic drugs to control
seizures. The
anticonvulsant effect of B6 vitamers may be propagated by multiple mechanisms including direct antagonist action on
ion channels,
antioxidant action on excess
reactive oxygen species generated by increased neuronal firing and replenishing the pool of
pyridoxal 5'-phosphate needed for the synthesis of some inhibitory
neurotransmitters.
Vitamin B6 may be a promising adjunctive treatment for patients with
channelopathies and the wider epileptic population. This report also demonstrates that an abnormal plasma to CSF
pyridoxal 5'-phosphate ratio may not be exclusive to inborn errors of
vitamin B6 metabolism.