Mild malformation of cortical development with oligodendroglial hyperplasia: a new pathological subtype of frontal lobe epilepsy

Abstract

Objective To analyze the clinical and histology characteristics of a patient with frontal lobe epilepsy diagnosed with mild malformation of cortical development with oligodendroglial hyperplasia, and to recognize the new neuropathological entity. Methods Clinical history, seizure types, neuroimaging, electroencephalography as well as macroscope, histology and immunohistochemistry characteristics were collected from a frontal lobe epilepsy patient and were compared with cases from literature. Results It was a female patient aged 16 years with 12 years history of epilepsy. The seizures manifested as episodes of conscious loss with automatism including grope and voice lasting for seconds. About 10 episodes a day were found and sometimes with secondary generalized tonic-clonic seizures. MRI showed blurring of grey-white matter interface in left orbital frontal cortex. Video-encephalography revealed left frontal lobe origin of seizures. So left prefrontal lobe was removed. Histology showed almost normal cortex neuropil and neurons. Blurring of grey-white interface in some area with patches of proliferation of oligodendrocytes in the corresponding sub-cortical white matter was found. The density of oligodendrocytes was significantly higher in sub-cortical than in deep white matter both shown in HE and Oligo-2 staining. Obvious oligodendrocytes increase and satellite phenomenon in deep cortical layer as well as increased ectopic neurons in sub-cortical white matter were found in the lesion. In proliferation area, there were some nuclei stained with Ki-67, but not as high as tumor. Subsequent follow up for two years proved the operation efficacy and benign prognosis. Conclusions There are special and undiscovered histopathological entities in epilepsy etiology. Although known as grey matter disease, white matter pathology plays an important role in epilepsy pathophysiology which needs further research. Key words: Epilepsy, frontal lobe; Oligodendroglia; Malformation of cortical development