Clinical manifestations, MRI abnormalities, learning disabilities, and effect of pyridoxine dose on intelligence quotients were studied in 6 definite and 3 possible cases of pyridoxine dependent seizures in children, ages 2.5 to 14 years, seen at Newcastle General Hospital, Newcastle upon Tyne, UK. Additional presenting features included jitteriness, encephalopathy, neonatal dystonia, hepatomegaly, and abdominal distension with bilious vomiting. Abnormal fetal movements, a hammering sensation, were noted in 4. Later complications included break-through seizures with fever, visual agnosia, squint, articulatory apraxia, motor delay and dyspraxia, macrocephaly, and hydrocephalus. MRI showed focal thinning of the posterior third of the corpus callosum, cerebellar hypoplasia, and mild cerebral atrophy. Psychometric tests revealed specific impairments of expressive language with relative preservation of receptive verbal comprehension. IQ scores were below average (Full scale 50 to 73), but showed improvements after pyridoxine dose increases, particularly in the performance subscale. EEG abnormalities disappeared following pyridoxine therapy. 
COMMENT. The diagnosis of pyridoxine-dependent seizures is based on clinical features and an absolute response to pyridoxine, recurrence after pyridoxine withdrawal, and immediate control after re-introduction. Language and cognitive disabilities may be partially reversible with optimal dosage.