Mild malformation of cortical development with oligodendroglial hyperplasia and epilepsy (MOGHE)

Mild malformation of cortical development with oligodendroglial hyperplasia and epilepsy (MOGHE) is a histopathological entity primarily associated with drug-resistant frontal lobe epilepsy. MOGHE is characterized by a distinct histological phenotype that includes blurred gray-white matter boundaries, heterotopic neurons in the white matter, and increased numbers of subcortical oligodendroglial cells ^1,2.

Epidemiology

MOGHE is rare and has been primarily identified in patients with severe, drug-resistant epilepsy, especially those with frontal lobe involvement ¹. Patients are typically children or young adults ^1,2,4.

Clinical presentation

Patients with MOGHE typically present with drug-resistant epilepsy, which may include various seizure types such as atonic, tonic, and focal seizures. Cognitive impairment is also common, with a decline in intellectual abilities over time ¹.

Pathology

Histologically, MOGHE is characterized by blurred gray-white matter boundaries, and patchy multifocal increase in the number of subcortical oligodendroglial cells within the white matter. These cells show increased proliferative activity, indicated by nuclear Ki-67 labeling , compared to focal cortical dysplasia, similar to that seen in DNETs, but far lower than oligodendrogliomas ¹.

Although some heterotopic neurons are present, these are confined in the superficial subcortical white matter, and not present more deeply ¹.

Importantly, the cortex demonstrates preserved six-layered architecture of with no radial microcolumns, horizontal dyslamination, dysmorphic neurons or balloon cells, thus not fulfilling criteria for focal cortical dysplasia ¹.

Areas of hypomyelination are also present, that influence MRI features ^1,2,4.

Classification

MOGHE has been added as an entry in the 2022 updated International League Against Epilepsy (ILAE) consensus (Blumcke) classification of focal cortical dysplasia under the subheading "white matter" ³.

Radiographic features

MRI

MRI is crucial for the diagnosis of MOGHE. Although generally similar to focal cortical dysplasia Type IIa, there are some differences. MOGHE typically demonstrates the following features ¹:

• blurred gray-white matter boundary

• increased FLAIR signal

• absence of transmantle sign

• frontal lobe location

• multifocal distribution

Additionally, MRI features appear to vary with age, possibly due to changes in myelination, and have been divided into two subtypes ²:

• subtype I

  • younger patients (<5 years of age)

  • laminar subcortical hyperintensities on T2 and FLAIR

• subtype II

  • older patients

  • reduced corticomedullary differentiation secondary to reduced T2/FLAIR subcortical signal

Treatment and prognosis

The primary treatment for MOGHE is surgical resection of the affected brain tissue ¹. If complete resection is achieved, this generally results in significant improvement in regards to epilepsy ⁴.

History and etymology

The acronym MOGHE was first introduced in 2017, originally for "mild malformation of cortical development with oligodendroglial hyperplasia" ¹. Subsequent literature attributes the final "E" to an appended "and epilepsy" although, in fairness, it is difficult to understand how exactly the acronym MOGHE was derived.

Differential diagnosis

The primary differential diagnosis is that of focal cortical dysplasia (particularly type IIa) ⁴.

• very similar MRI features

• MOGHE more common in the frontal lobes

• MOGHE more likely multifocal