September 1, 2016
A 46-year-old patient presents with a history of epilepsy, but otherwise no other relevant past medical history.
Extraventricular Neurocytoma
- Background:
- Neurocytomas are uncommon neoplasms. Most neurocytomas present as intraventricular masses near the foramen of Monro. Extraventricular neurocytoma (EVN) by definition are located within the brain parenchyma. Children and young adults are more frequently affected (median age 34 years). EVNs show no obvious sex predilection.
- EVNs are mainly found in the frontal (46%) and parietal (23%) regions, but can be located anywhere along the neuroaxis.
- Clinical Presentation:
- Symptoms are non-specific. They can present with headache, dizziness, visual impairment, seizures, or focal defictis, depending on the size and localization of the tumor.
- Key Radiologic Features:
- These tumors frequently present as a well-circumscribed (75%) mass, with cystic degeneration (58%), mild or moderate perilesional edema (51%), calcification, and hemorrhage. Enhancement is common (92%), but the degree and pattern of enhancement are variable.
- MRS shows increased Cho/Cr ratio and decreased NAA/Cr ratio, and PWI demonstrates elevated cerebral blood volume (CVB), as other enhancing brain neoplasms.
- The imaging characteristics of EVNs have significant overlap with oligodendrogliomas. Both present similar morphologic features and perfusion patterns (elevated CVB even in low grade lesions, and Choline/Cr ratio).
- Therefore the diagnosis requires biopsy.
- Histopathologic Features:
- Positive antibody reaction to synaptophysin, glial fibrillary acidic protein (GFAP), neurofilament and NeuN.
- Differential Diagnoses:
- Oligodendroglioma, astrocytoma, dysembryoplastic neuroepithelial tumor: As stated before, the imaging characteristics are non-specific for EVNs, as there is significant overlap with other CNS tumors.
- Treatment:
- After complete resection most neurocytomas do not recur. Subtotal resection is associated with an increased likelihood of recurrence.
