Seizure outcome following primary motor cortex-sparing resective surgery for perirolandic focal cortical dysplasia

Abstract

Objectives: We present a case series of patients who underwent perirolandic resection for medically refractory focal epilepsy due to focal cortical dysplasia (FCD). Our aim was to specifically evaluate the outcome of a surgical strategy intended for seizure freedom while preserving primary motor cortex function.

Materials and methods: Thirteen patients undergoing perirolandic resection for pharmacoresistant focal epilepsy between 2010 and 2015 who demonstrated histological evidence of FCD were selected from a prospectively maintained database. Presurgical evaluation included video EEG telemetry and 3T MRI brain for all patients. Eight patients underwent interictal FDG PET scan. Intracranial EEG monitoring was done for 8 patients - six by conventional subdural grid and depth electrodes and two by Stereo EEG. Additional techniques included extraoperative cortical stimulation mapping, intraoperative electrocorticography (ECoG), intraoperative motor cortex mapping and awake surgery in various combinations. In all cases (lesional and nonlesional), resection was intentionally limited for anatomic preservation of the primary motor cortex.

Results: Amongst the thirteen patients with age ranging 14-44 years (mean 26.8 ± 9.2) 62% of them had daily seizures. MRI abnormalities were identified in 8 patients (62%), PET showed concordant findings in 7 patients (88%). When utilized, the mean duration of intracranial EEG recordings was 8.0 ± 7.2 days (range 2-23 days). All patients underwent a primary motor cortex-sparing resection of the suspected epileptogenic cortex. The mean postoperative follow up period was 23 months (range 7.5-62 months). Twelve out of 13 (92%) were seizure free (Engel 1) outcome at the last follow-up assessment; one patient had Engel 2a outcome at 28 months. Six patients (46%) had immediate new focal neurological deficits, however all six patients had recovered completely within three months.

Conclusion: The surgical strategy of a primary motor cortex-sparing resective surgery for perirolandic FCD is associated with an excellent early seizure-freedom rate and no permanent neurological deficits. Since the ultimate goal of resective epilepsy surgery is seizure freedom with simultaneous functional preservation, similar long term outcome studies should ultimately guide the resection strategy.

Keywords: Epilepsy surgery; Epilepsy surgery outcome; Focal cortical dysplasia; Perirolandic epilepsy.