MRI, Magnetoencephalography, and Surgical Outcome of Oligodendrocytosis versus Focal Cortical Dysplasia Type I

Abstract

BACKGROUND AND PURPOSE:Abnormalities of oligodendrocytes have been reported in surgical specimens of patients with medically intractable epilepsy. The aim of this study was to compare the MR imaging, magnetoencephalography, and surgical outcome of children with oligodendrocytosis relative to focal cortical dysplasia I. MATERIALS AND METHODS:Oligodendrocytosis included oligodendroglial hyperplasia, oligodendrogliosis, and oligodendroglial-like cells in the white matter, gray matter, or both from children with medically intractable epilepsy. Focal cortical dysplasia I included radial and tangential cortical dyslamination. The MR imaging, magnetoencephalography, type of operation, location, and seizure outcome of oligodendrocytosis, focal cortical dysplasia I, and oligodendrocytosis ϩ focal cortical dysplasia I were compared. RESULTS:Eighteen subjects (39.1%) had oligodendrocytosis, 21 (45.7%) had focal cortical dysplasia I, and 7 (15.2%) had oligodendrocytosis ϩ focal cortical dysplasia I. There were no significant differences in the type of seizures, focal or nonfocal epileptiform discharges, magnetoencephalography, and MR imaging features, including high T1 signal in the cortex, high T2/FLAIR signal in the cortex or subcortical white matter, increased cortical thickness, blurring of the gray-white junction, or abnormal sulcation and gyration among those with oligodendrocytosis, focal cortical dysplasia I, or oligodendrocytosis ϩ focal cortical dysplasia I (P Ͼ .01). There were no significant differences in the extent of resection (unilobar versus multilobar versus hemispherectomy), location of the operation (temporal versus extratemporal versus both), or seizure-free outcome of oligodendrocytosis, focal cortical dysplasia I, and oligodendrocytosis ϩ focal cortical dysplasia I (P Ͼ .05). CONCLUSIONS:Oligodendrocytosis shared MR imaging and magnetoencephalography features with focal cortical dysplasia I, and multilobar resection was frequently required to achieve seizure freedom. In 15% of cases, concurrent oligodendrocytosis and focal cortical dysplasia I were identified. The findings suggest that oligodendrocytosis may represent a mild spectrum of malformations of cortical development.ABBREVIATIONS: EEG ϭ electroencephalography; FCD ϭ focal cortical dysplasia; ILAE ϭ International League Against Epilepsy; MEG ϭ magnetoencephalography;MEGSS ϭ MEG spike sources; MOGHE ϭ mild malformation of cortical development with oligodendroglial hyperplasia; PD ϭ proton density; ST ϭ slice thickness

Multilobar unilateral hypoplasia with emphasis on the posterior quadrant and severe epilepsy in children with FCD ILAE Type 1A

“…Surgical resection and/or disconnection procedures successfully controlled seizures in 47% of the children over a median follow‐up period of 4.2 years, that is, Engel class I. This figure is in line with other studies reporting seizure‐freedom rates between 21% and 57.1% in children with isolated FCD Type 1 32,35,40,45,46,52 . Notwithstanding, surgical resection borders were often very difficult to determine in these children.…”

“…56,57 An age at seizure onset younger than age 3 months is reported in only three of the many recent reports about patients with FCD ILAE Type 1, yet without further FCD1 subtype specification. 35,46,52 The observation that the affected children do not present with seizures during the first weeks of life might be helpful in the differential diagnosis of various epileptic and developmental encephalopathies, in which very early seizure onset is common and genetic causes are increasingly recognized. 2,3 The high percentage of patients in our series being severely mentally retarded is outstanding compared to children with other epileptogenic lesions restricted to one hemisphere, for example,.…”

“…Three FCD1 subtypes have been defined therein when assessing architectural patterns of either vertical (FCD 1A), horizontal (FCD 1B), or mixed vertical and horizontal (FCD 1C) abnormalities of the neocortex 16 . Currently published patient cohorts assembled all three FCD1 subtypes together 31–47 . The rare number of patients with a histopathologically defined FCD1 subtype might be a major reason.…”

Definitions and classification of malformations of cortical development: practical guidelines

“…Finally, an asymmetric lack of subcortical myelination is a rather specific finding for FCD type Ia ( Barkovich and Raybaud, 2019 ). Remarkably, the differential diagnosis includes low grade tumours, such as gangliogliomas, as well as new histological entities, such as ‘oligodendrocytosis’ ( Mata-Mbemba et al , 2018 ) and ‘mild malformation of cortical development with oligodendroglial hyperplasia (MOGHE)’( Schurr et al , 2017 ), characterized on MRI by abnormal signal intensities within the anatomical region of seizure onset.…”

Narrative review of epilepsy: getting the most out of your neuroimaging

“…Main neuroimaging features of FCD:  Thickening of the cortex;  Blurring of white-grey matter junction with abnormal architecture of subcortical layer;  White matter hyperintensity in T2/FLAIR sequences;  T1 or T2 hyperintensity of the cortex;  "Transmantle sign" (characteristic of the FCD type II-B) (Figure 7). The most used classification of FCD is represented by Blumcke classification (45).…”