Clinical implications of scalp ictal EEG pattern in patients with temporal lobe epilepsy

To determine the clinical implications of scalp ictal EEG pattern in patients with temporal lobe epilepsy (TLE).

Scalp EEG ictal patterns were retrospectively determined in 27 consecutive patients with medically refractory temporal lobe epilepsy who underwent phase-1 scalp video-EEG and phase-2 simultaneous scalp and intracranial video-EEG recordings for pre-surgical evaluation.

Of the 192 temporal lobe seizures recorded during phase-1 and phase-2 scalp video-EEG studies, 124 (65%) seizures were associated with theta/alpha (5-9 Hz) ictal onset pattern, and 68 (35%) seizures were associated with delta (2-5 Hz) ictal onset pattern. Fourteen (52%) patients had exclusively theta/alpha ictal onset, 3 (11%) patients had exclusively delta ictal onset, and 10 (37%) patients had mixed theta/alpha and delta ictal onsets. MTLE was observed in 26 patients who had 124 seizures with theta/alpha ictal onset and 59 seizures with delta ictal onset. LTLE was observed in one patient who had 9 seizures with delta ictal onset. Scalp ictal EEG pattern was not significantly correlated with postsurgical seizure outcomes.

Both scalp delta and theta/alpha ictal onset patterns can be commonly found in patients with MTLE.

Scalp delta ictal onset is not a unique EEG pattern for LTLE as commonly believed.