Clinical characteristics and postoperative seizure outcome in patients with mild malformation of cortical development and oligodendroglial hyperplasia

Abstract

Objective: We describe for the first time clinical characteristics in a series of 20 pre-surgically investigated patients with mild malformation of cortical development with oligodendroglial hyperplasia (MOGHE) who were operated on in our epilepsy center. We aimed to better diagnose this entity and help surgical planning.Methods: Data on 20 patients with histologically confirmed MOGHE were retrospectively evaluated as to age at epilepsy onset and operation, seizure semiology, magnetic resonance imaging (MRI) localization, electroencephalography (EEG) patterns, extent of the operative resection, and postoperative seizure outcome.Results: Epilepsy began mainly in early childhood; however, symptoms did not manifest until adolescence or adulthood in 30% of patients. All patients had pathologic MRI findings. In 45% of patients the lesion was initially overlooked. Most commonly, the lesion was seen in the frontal lobe. Seizure semiology was characterized as follows: (1) epileptic spasms at epilepsy onset were common and (2) nocturnal hyperkinetic seizures during the course of the disease were rare. EEG always showed frequent interictal epileptic discharges. Two peculiar patterns were observed: (1) during sleep stage I-II, sub-continuous repetitive (0.5-1.5/s) unilateral plump spike/polyspike slow waves were seen and ( 2) during wakefulness, unilateral paroxysms of 2-2.5/s spike-wave complexes occurred. In total, 60% of patients were seizure-free 1 year postoperatively. Postoperative seizure outcome was positively correlated with the extent of resection, age at epilepsy onset, and age at operation. Postoperative long-term outcomes remained stable in patients undergoing larger operations.Significance: MRI, EEG, and semiology already contribute to the diagnosis of probable MOGHE preoperatively. Because postoperative seizure outcomes depend on the extent of the resection, prior knowledge of a probable MOGHE helps to plan the resection and balance the risks and benefits of such an intervention. In

The ILAE consensus classification of focal cortical dysplasia: An update proposed by an ad hoc task force of the ILAE diagnostic methods commission

“…Reported cases involve young children with frontal lobe epilepsy, or temporal plus epilepsy, with a median seizure onset at age 2 years (range 0.3–13 years) 20 . In a retrospective clinical study of 20 patients with MOGHE, postoperative seizure outcome depended largely on the extent of the resection, with a good Engel class I outcome reported for all patients with large resections 24,25 . MOGHE represents a distinct mMCD subtype, with 45%–100% of studied patients harboring SLC35A2 somatic variants 13,17 .…”

“…13,17 These results argue for the inclusion of MOGHE as a distinct pathological entity that preferentially affects the white matter of patients with early-onset epilepsy and is amenable to epilepsy surgery. 25 3.1.2 | Neurophysiology FCDII subtypes became much better characterized as clinical entities with well-defined EEG signatures in FCDIIa and IIb subtypes. The specificity of interictal patterns such as focal continuous rhythmic discharges and repetitive spiking have been suggested as possible predictors of the ictal-onset zone and of favorable postresection seizure outcome.…”

“…20 In a retrospective clinical study of 20 patients with MOGHE, postoperative seizure outcome depended largely on the extent of the resection, with a good Engel class I outcome reported for all patients with large resections. 24,25 MOGHE represents a distinct mMCD subtype, with 45%-100% of studied patients harboring SLC35A2 somatic variants. 13,17 One study also showed that SLC35A2-mutated brain tissue had an aberrant pattern of glycosylation.…”

Clinical Features, Neuropathology, and Surgical Outcome in Patients With Refractory Epilepsy and Brain Somatic Variants in the SLC35A2 Gene

“…We found a weak association between improved postoperative cognitive outcome and lower brain VAF, but this finding was not confirmed in regression analyses, possibly due to the small sample size. 8,11,17…”

“…13 In the recently updated FCD classification, MOGHE has been proposed as a new category to be included. 14 Although various series 13,[15][16][17][18] have explored the clinical, EEG, and neuroimaging features and postoperative seizure outcome in patients with MOGHE, limited information is available regarding specific brain somatic SLC35A2 variants and their associated outcomes after surgery. In this study of 47 patients with brain somatic SLC35A2 gene variants, we analyzed clinical, neuroimaging, EEG, histopathologic, and genetic findings and assessed factors influencing postoperative seizure and cognitive outcomes.…”