Introduction: Pyridoxine-dependent epilepsy (PD) is defined by therapy-resistant seizures that respond to intravenous administration of pyridoxine (pyridoxine-IV). Patients are identifiable by ALDH7A1-gene mutation and/or increased urine-alpha-AASA concentration. In the present study, we aimed to investigate whether specific EEG responses during pyridoxine-IV allow instantaneous recognition of PD by ALDH7A1 gene mutation.

Method: Online EEG registrations of 50 mg pyridoxine-IV were compared between PD (ALDH7A1 gene mutation (n  =  3, six trials)) and non-PD (n  =  9, nine trials). Urine-α-AASA concentrations were >9 mmol/mmol creatine (PD) and <1 (non-PD). 5–15 minutes before and after pyridoxine-IV, EEG segments were digitally analysed for average background amplitude and total and relative power. Total power indicates the magnitude of background activity per frequency band. Relative power indicates the contribution of a frequency band to the spectrum.

Results: After pyridoxine-IV, epileptic activity persisted in three of three PD and eight of nine non-PD infants (5/6 versus 8/9 trials, respectively). Intra-individually, two PD infants showed a large variation in amplitude responses between consecutive trials (−64 to 39% and −44 to −26%, respectively). In both PD and non-PD: (1) pyridoxine-IV did not affect relative power; (2) central amplitude decreased (5/6 PD trials; −64 to 39% versus 8/9 non-PD trials; −45 to 15%) and (3) total power decreased (PD −56 to 41%; −71 to +31%; −66 to +2% and non-PD −43 to 14%; −29 to 27%; −54 to 2%; p<0.05, in delta, theta and beta frequency bands, respectively).

Conclusion and Discussion: Pyridoxine-IV causes non-specific EEG responses that prohibit instantaneous recognition of PD by ALDH7A1 gene mutation. These data imply that infants with therapy-resistant seizures should receive pyridoxine until PD is excluded by metabolic and/or DNA analysis.