Abstracts

Rationale: Disconnection epilepsy surgery has been evolving as a replacement for lobar-multilobar resection surgery in patients with intractable posterior quadrant (PQ) epilepsy with varied seizure outcomes between 57-90%. The aim of this study is to evaluate effectiveness of tailored posterior quadrant disconnection (PQD) for medically refractory posterior quadrant epilepsy.

Methods: The authors conducted a retrospective analysis of clinical, electroencephalography, structural and functional brain imaging, histopathological, surgical and seizure outcome data of patients undergoing PDQ at our epilepsy center between 2012 and 2019.

Results: 19 consecutive patients included 12 adults and 7 children. Seizure started between the ages of 3 weeks to 74 years with median epilepsy duration of 12.1 years. PQD was performed between the ages of 4 to 74.5 years including in 6 patients (31.5%) with prior failed surgery. 12/19 (63.1%) patients had more than one seizure type with focal impaired awareness seizure as the most common seizure type. Etiologies included malformation of cortical development (n=8), acquired hemorrhagic brain injury (n=3), unknown (n=3), primitive neuro-ectodermal tumor (n=1), perinatal hypoxic ischemic injury (n=1), perinatal stroke (n=1), venous stroke/cerebral venous thrombosis (n=1) and CHRNA4 gene mutation (n=1). Ictal findings localized to unilateral temporo-parietal-occipital region in 15 patients (78.9%), unilateral frontal region and non-lateralizing in 2 patients each. Unilateral PQ epileptogenic lesion on brain MRI was seen in 7 patients (36.8%), bilateral MRI pathology in 5 (26.3%) and ipsilateral frontal region in 6 patients (31.5%). PET hypometabolism in the ipsilateral PQ was noted in 13 (68.4%), unilateral hemispheric hypometabolism in 2 and ipsilateral frontal hypometabolism in 1 patient. Ictal hyperperfusion showed concordant ipsilateral PQ data in 7 (36.8%) and beyond PQ in 4 patients (21%). Magnetoencephalography source localization to ipsilateral PQ was in 12 (63.1%) and contralateral frontal region in 1 patient. All patients underwent invasive EEG with unilateral subdural electrodes (n=18), stereotactic depth electrodes (n=3) and bilateral stereo EEG (n=1). Isolated PQD was performed in 6 patients (31.5%), combined with tailored resection of adjacent lobe in 10 (52.6%), combined with frontal disconnection in 2 (10.5%) and tuberectomy in 1 patient. Transient perioperative complications occurred in 7 patients (36.8%). Overall, 82.3% patients (14/17; 2 lost to follow up) became completely seizure free at 2-year follow up and 52.9% remained seizure-free since surgery. Histopathology showed focal cortical dysplasia in 7 patients (36.8%). Neurological deficits included contralateral homonymous hemianopsia (n=12, 66.6% ), contralateral hemiparesis (n=3, 16.6%) and right facial paresis (n=1, 5.5%) which remained stable over time. There was no statistical difference in seizure outcome between developmental versus acquired pathology.

Conclusions: PQD with customized extent of surgery is an effective and reasonably safe procedure in selected patients with complex PQ epilepsy involving heterogenous anatamo-electro-clinical data.

Funding: Please list any funding that was received in support of this abstract.: None.