Seizure outcome in drug-resistant epilepsy in the setting of polymicrogyria

Objective

We aimed to analyze seizure outcomes and define ictal onset with intracranial electroencephalography (ICEEG) in patients with polymicrogyria (PMG)-related drug-resistant epilepsy (DRE), considering surrounding cortex and extent of surgical resection.

Methods

Retrospective study of PMG-diagnosed patients (2001 to June 2018) at a single epilepsy center was performed. Primary outcome was complete seizure freedom (SF), based on Engel classification with follow-up of ≥ 1 year. Univariate analyses identified predictive clinical variables, later integrated into multivariate Cox proportional hazards models.

Results

Thirty-five patients with PMG-related DRE (19 adults/16 pediatric: 20 unilateral/15 bilateral) were studied. In surgical group (n = 23), 52 % achieved SF (mean follow-up:47 months), whereas none in non-resective treatment group (n = 12) attained SF (mean follow-up:39.3 months) (p = 0.002). In surgical group, there were no significant differences in SF, based on the laterality of the PMG [uni or bilateral,p = 0.35], involvement of perisylvian region(p = 0.714), and extent of the PMG resection [total vs. partial,p = 0.159]. Patients with ictal ICEEG onset in both PMG and non-PMG cortices, and those limited to non- PMG cortices had a greater chance of achieving SF compared to those limited to the PMG cortices.

Conclusion

Resective surgery guided by ICEEG for defining the epileptogenic zone (EZ), in DRE patients with PMG, leads to favorable seizure outcomes. ICEEG-guided focal surgical resection(s) may lead to SF in patients with bilateral or extensive unilateral PMG. ICEEG aids in EZ localization within and/or outside the MRI-identified PMG. Complete removal of PMG identified on MRI does not guarantee SF. Hence, developing preimplantation hypotheses based on epileptogenic networks evaluation during presurgical assessment is crucial in this patient population.