LONGITUDINAL MRI FINDINGS IN PYRIDOXINE-DEPENDENT SEIZURES

Background: Pyridoxine dependency is an uncommon familial cause of int ractable seizures in newborns and infants. Fewer than 100 patients hav e been reported, and only four reports have included examples of brain imaging findings. We report the first longitudinal MRI findings in tw o patients with this condition. Methods: Six brain MR scans, three eac h from two patients with pyridoxine-dependent seizures, were reviewed. Morphometry of selected axial images was performed to calculate the v entricle-to-brain ratio (VBR). Patients: A girl, followed for 5 years, presented with intrauterine fetal seizures and neonatal seizures, and pyridoxine dependency was confirmed at 3.5 months of age. This patien t had a subsequent history of poor compliance with pyridoxine therapy and severe developmental disability. A boy, followed for 9 years, pres ented with neonatal seizures, and pyridoxine dependency was diagnosed at 8 months of age. Results: The serial MR scans demonstrated progress ive dilation of the ventricular system and atrophy of the cortex and s ubcortical white matter together with an increase in the VER. These pr ogressive abnormalities were greater in the 5-year-old girl. Conclusio n: Pyridoxine-dependent seizures are due to an inborn abnormality in t he pyridoxine-dependent synthesis of gamma-aminobutyric acid (GABA). T he progressive MR changes may be due to chronic excitotoxicity caused by an imbalance of cerebral levels of GABA and glutamic acid.