Work

Impact of antiseizure medication taper on electroencephalographic dynamics in focal epilepsy: A stereoelectroencephalographic study

Year: 2026

Type: article

Abstract: OBJECTIVE: Tapering of the antiseizure medication dosage in the epilepsy monitoring unit can provoke seizures, but its effects on seizure dynamics remain poorly characterized. This study addresses three questions: (1) Does antiseizure medication tapering influence spatiotemporal dynamics of seizures? (2) Does the tapering rate affect these dynamics? (3) Does tapering have a similar effect on interictal epileptic discharges as it does on seizures? METHODS: Patients with drug-resistant epilepsy undergoing stereoelectroencephalographic (stereo-EEG) presurgical evaluations at Duke University Medical Center (n = 104) and the Montreal Neurological Institute and Hospital (n = 80) were screened. We included patients in whom the antiseizure medication dosage was tapered from the highest daily dosage (high dosage) to ≤ 50% (low dosage) during stereo-EEG monitoring, and at least one seizure from the same focus was recorded in both conditions. Using an intrapatient design, we compared seizure onset-zone, onset pattern, and propagation dynamics between the two conditions. Given the intrinsic seizure variability, comparisons were made between same-dosage and cross-dosage seizure pairs. We further assessed effects of tapering rates and examined the characteristics of interictal epileptiform discharges. RESULTS: Among 30 patients, the proportion of channels in the seizure onset zone did not differ between high-dosage and low-dosage conditions (7.25% vs. 8.95%, p = .50, d = -.04). Similarly, no differences were observed in the overlap ratio of seizure-onset regions (62% vs. 64%, p = .72, d = -.01), or the cross-correlation of seizure-onset patterns (.36 vs. .35, p = .54, d = .04) when comparing same-dosage versus cross-dosage seizure pairs. Conversely, seizures at low dosage involved more channels (40.71% vs. 81.49%, p = .001, d = -.39) and lasted longer (33.36 s vs. 74.30 s, p < .01, d = -.47). Tapering rate did not affect seizure dynamics. The mean interictal epileptiform discharge rate and number of propagation channels also remained unchanged. SIGNIFICANCE: Despite seizure exacerbation during antiseizure medication tapering, seizure-onset location remained stable. This supports the robustness of seizure-based localization even under reduced medication levels and rapid tapering regimens.

Source: Epilepsia

DOI: 10.1002/epi.70149