Abstracts

Malformations of cortical development (MCD) are a significant cause of chronic epilepsy. Inconsistent histopathologic classification of MCD has created diagnostic confusion and, at times, obscured clinical relevance. This study attempts to mitigate ongoing confusion and offer clinical correlation by utilizing a practical immunohistochemical protocol that allows reproducible histopathologic description within a contemporary MCD classification system. Searching the Mayo Clinic pathology database from 1/1987 to 1/2003, a cohort of 54 patients (34 male) with a previous histologic diagnosis of MCD was identified. The cohort[rsquo]s medical records were reviewed and relevant clinical data was abstracted. Available tissue from each patient was resectioned, stained with H[amp]E and Luxol Fast Blue, and immunostained for neurofilament and glial fibrillary acidic proteins. A blinded neuropathologist reviewed each specimen and classified the findings as either: architectural dysplasia, cytoarchitectural dysplasia without balloon cells, cytoarchitectural dysplasia with balloon cells, or polymicrogyria. A MCD was identified in 49/54 patient specimens. Ten patients exhibited architectural dysplasia only; eleven patients exhibited cytoarchitectural dysplasia characterized by large dysmorphic neurons in addition to altered cortical lamination; and nineteen patients possessed cytoarchitectural dysplasia characterized by large dysmorphic neurons and balloon cells. Balloon cells demonstrated varied neuronal and/or glial immunoreactivity. Nine patients had findings consistent with polymicrogyria. Gliosis, [ldquo]no pathology[rdquo], or mesial temporal sclerosis was found in five patients with a previous histologic diagnosis of MCD. The overall concordance between original diagnosis and diagnosis utilizing a contemporary MCD classification scheme was 90%. Patients possessing polymicrogyria demonstrated earlier seizure onset and increased seizure frequency, while, those with architectural dysplasia developed later onset epilepsy. Malformations of cortical development characterized by cytoarchitectural dysplasia (with or without balloon cells) had similar pre-surgical clinical presentations in terms of seizure onset and frequency. This study examines a relatively large epilepsy surgical cohort and presents a practical yet systematic pathologic approach to malformations of cortical development. Using standard immunohistochemistry and a recently published classification scheme, consistent description of MCD is achieved and, notably, offers improved diagnostic precision. As seen in previous studies, patients with polymicrogyria present with more severe epilepsy than patients with architectural or cytoarchitectural dysplasia. Historical features alone cannot accurately differentiate patients who possess balloon cells from those patients with cytoarchitectural dysplasia alone.