Abstracts

Rationale: Polymicrogyria (PMG) is a malformation of cortical development (MCD). It often results in medically refractory epilepsy. There is limited data on surgical outcomes, especially in setting of multifocal or diffuse bilateral polymicrogyria (DBP). Variable concordance between the epileptogenic zone and extra lesional involvement makes surgery more challenging.

Methods: Clinical data and diagnostics were reviewed retrospectively.

Results: Case1:A 2-year-old female presented with seizures since day 7 of life with epileptic spasms. After initial improvement with vigabatrin, she developed focal tonic clonic seizures with right arm flexion, head and gaze deviation to left with left arm and leg jerking. EEG showed focal right hemispheric slowing with diffuse epileptiform activity. MRI brain showed multifocal PMG in the rightfrontal and parietal lobes. A functional hemispherectomy was suggested at age one year but parents were reluctant. Seizures remained refractory despite multiple ASMs. She then developed super refractory status epilepticus in setting of adenovirus infection. EEG had now progressed to generalized bursts of paroxysmal fast activity with generalized spike wave discharges and poor organization. She developed focal weakness in left arm and leg with swallowing and breathing regression. Urgent palliative resection with intra-operative electrocorticography (ECoG) showed seizures captured from superior frontal gyrus and intraparietal sulcus, which were resected. She had focal seizures for 2 weeks in the immediate post-operative period, but since has been seizure free for over 4 months with wean of few ASMs. She now feeds by mouth, says few words, ambulates with improving left sided weakness. Case 2: A 17-year-old male with DBP, presented with seizure at age 6 years. Type I seizure is focal impaired seizure with axial tonic stiffening and Type II starts with autonomic seizure, were non localizing on scalp EEG. PET scan revealed hypermetabolic in right frontal and parietal regions. The decision was to proceed with vagal nerve stimulator (VNS), which failed to improve seizure control. Inter-ictal EEG in 2020 revealed right greater than left temporal epileptiform discharges. Ictal onset thought to be from the right temporal and frontal regions. Neuropsychology evaluation was consistent with mild global cortical dysfunction with right greater than left hemispheric dysfunction. SEEG was based on a hypothesis of right temporal-parietal occipital junction network with secondary involvement of left posterior perisylvian area. 23 habitual seizures with onset from the right angular gyrus with rapid spread to the right anterior cingulate and 8 subclinical seizures from the left dysplastic cortex were recorded. Two step resections, first of right angular gyrus resulted in 3 months freedom, then right anterior cingulate with one breakthrough seizure at 4 month follow up.

Conclusions: Our case series highlights that epileptogenic zone may be limited to only a part of PMG and SEEG helps guide a tailored resection with seizure reduction, freedom and improvement neurocognitive skills without significant clinical deficits.

Funding: Please list any funding that was received in support of this abstract.: Not funded.