FIRDA, refractory epilepsy, and SEEG-guided RF: A case report

We will demonstrate that FIRDA (frontal intermittent rhythmic delta activity)-otherwise related to systemic disorders and encephalopathy-has a role as an epileptic biomarker of deep-seated midline SOZ. Its abolishment following SEEG-guided radiofrequency of such SOZ correlates with clinical improvement suggesting its role as a noninvasive biomarker of otherwise inaccessible SOZs.

We report the case of AK who was admitted with "psychiatric and gastrointestinal complaints." AK's complaints were further associated with FIRDA during VEEG. His previous refractoriness to AEDs, the clinico-electroencephalographic correlation, MRI showing bilateral hippocampal atrophy (more to the left) and severe memory deficits, prompted us to suggest a left temporo-mesial SOZ, for which SEEG was done. Dual SEEG and scalp electrodes were used primarily for diagnostic purposes but taking into account an option for a therapeutic action by RF ablation.

The dual array demonstrated a clear association between left hippocampal high voltage spikes and HFOs on SEEG recordings with FIRDA on concomitant scalp EEG parallel to behavioral changes, as suspected in our preliminary hypothesis. A further RF ablation eliminated the epileptiform activity (Spikes, HFOs, and FIRDA) followed by clinical improvement.

This is the first report showing the clinical significance of FIRDA associated with behavioral changes as a marker for latent refractory mesial epilepsy. SEEG exploration has the potential to uncover deep sources, which are manifested as FIRDA on scalp EEG. These abnormalities and clinical symptoms can be eliminated by RF ablation.