Abstracts

Pyridoxine dependency is a rare autosomal recessive disorder, usually presenting in children under 1 year of age with therapy-resistant seizures (defined as seizures unresponsive to at least 2 first-line anti-epileptic drugs). The pyridoxine dependent seizures have been ascribed to low concentrations of the co-factor pyridoxal phosphate leading to glutamate accumulation and gamma amino-butyric acid (GABA) depletion. The diagnosis pyridoxine dependency is empirically assessed when seizures stop after intravenous (IV) pyridoxine administration and recur after pyridoxine withdrawal. It is therefore recommended to administer an empirical IV dose of pyridoxine to infants with therapy-resistant seizures. However, the general electro-encephalographic (EEG) effect of pyridoxine administration in infants with therapy resistant seizures is still unknown. This information may help to discriminate whether or not altered EEG characteristics in individual patients are attributable to pyridoxine dependency. In infants under 1 year of age with therapy-resistant seizures, we aimed to determine the effect of empirical IV pyridoxine administration on EEG activity. In 10 infants with therapy-resistant seizures (median age 2 months; range 0-11 months), the effect of pyridoxine administration (100 mg IV) on the simultaneously registered EEG was digitally assessed. Before and after IV pyridoxine administration, EEG segments of identical vigilance/behavioral states were digitally compared for amplitude, magnitude per frequency band (total power), and percentage of the frequency band within the total spectrum (relative power). In infants with therapy-resistant seizures, intravenous (IV) pyridoxine administration significantly reduced the EEG amplitude over the frontal (-21%, p[lt]0.05) and central (-11%, p[lt]0.05) area. In the central area, IV pyridoxine decreased total power in all frequency bands studied (delta -7%, p[lt]0.05, theta -7%, p[lt]0.05, and beta -10%, p[lt]0.05). IV pyridoxine did not affect relative power. The reduction in amplitude and total power after IV pyridoxine administration was observed in both pyridoxine responsive (2 of 10) and irresponsive (8 of 10) infants. In infants under 1 year of age with therapy resistant seizures, IV pyridoxine affects EEG background activity. The reduction in amplitude and total power after IV pyridoxine seems to be a non-specific effect, which is independent of pyridoxine-responsiveness.