Abstract
Background: Extraventricular Neurocytoma (EVN) is a rare low grade neoplastic lesion that originates anywhere in the central nervous system, not involving the ventricular system; it usually presents itself in the frontal lobes, followed by temporal, parietal and occipital lobes, and, in rare cases, the sellar region or spinal cord. The following is a case report regarding an EVN located in the left frontal lobe, followed by a brief literature review. Case report: A 58 yo female, admitted with worsening of a chronic headache within the last 3 months, developing vertigo and frequent falls directed to her left side. During admission, she presented score 15 on the Glasgow Coma Scale (GCS), without any other change during the neurological examination. A brain Magnetic Resonance Imaging (MRI) was performed, showing a heterogeneous left frontal lesion, without contrast enhancement, with moderate to severe perilesional vasogenic edema, exerting mass effect and generating a marked midline shift. The initial diagnostic hypothesis was Glioma. A microsurgical resection of the lesion was performed, with a Soutar incision, followed by a left frontal rectangular craniotomy - the procedure was completed without any intraoperative complications. At hospital discharge, two days after surgery, the patient presented a contralateral complete and proportionate hemiparesis (grade IV+), maintaining the GCS of admission. The immunohistochemical results confirmed the diagnosis of extraventricular neurocytoma. The patient was submitted to adjuvant radiotherapy, and maintained outpatient follow-up without signs of remission. Discussion: EVN is an uncommon neoplastic lesion characterised as a neuronal and glial-mixed tumour. Because of its image and histological features, which may resemble other kinds of brain lesions (specially oligodendrogliomas), diagnostics difficulties may be present during histopathological analysis, which can include other non-related entities. It appears typically as a solitary, large (>40 mm), well-defined lesion, with moderate peritumoral edema and punctual calcifications. It usually originates in the white matter of the cerebral hemispheres, involving, most frequently, the frontal lobe. EVN is composed of small, round and uniform cells, with a clear cytoplasm and perinuclear halo and shows neuronal differentiation without atypical features, pleomorphism, proliferation or endothelial necrosis - low mitosis image counts are the norm, and a strong immune response to synaptophysin is present. Treatment for EVN is a combination of surgical resection, radiotherapy and, in some cases, chemotherapy. Conclusion: Regardless of its rarity and frequency, EVN should be remembered as a possible differential diagnosis for intracranial mass lesions. Therefore, this paper’s objective is to emphasise the role and importance of immunohistochemistry and neuronal biomarkers as means of diagnosis.
