Cystic meningioma showing peripheral rim enhancement without mural nodule.

Abstract

A 67-year-old female patient presented complaining of headache and vomiting which were present for the last 1 year and which worsened for the last 3 months. Her medical history was remarkable for DM type II and hypertension for the last 10 years. Her neurological physical exam was nonremarkable. Magnetic resonance images (MRI) of the brain revealed a dural based extra-axially located right parietal vertex cystic lesion with a dural tail, demonstrating a peripheral rim enhancement. There was no evidence of diffusion restriction on diffusion-weighted/ apparent diffusion coefficient mapping (Fig. 1). The patient had no known cancer history and the radiological findings were suggestive for a cystic meningioma. The histopathological evaluation of the excised mass revealed a meningothelial meningioma with focal microcystic changes (Fig. 2). Meningiomas are the most frequently encountered primary non-glial intracranial tumours and are usually solid. The coincidence of a cystic lesion along with a meningioma is quite rare, of varying ratios in different reports (1.6–10 %), and more frequent in males, children and along with malignant meningiomas [1, 2]. The classical radiological finding of cystic meningioma is a contrastenhancing solid component accompanied by a cyst [3]. The absence of the solid component leads to confusions in terms of radiologically differential diagnosis. The differential diagnosis of an extra-axially located cystic lesion includes arachnoid cyst, epidermoid cyst, dermoid cyst, cystic-necrotic metastasis, cystic schwannoma, and cystic meningioma. Epidermoid cysts are mostly located in the cerebello-pontine angle, and a diffusion restriction is typical. Arachnoid cysts do not demonstrate contrast enhancement. MRI findings of dermoid cysts are generally of high-signal intensity, due to their fat content. Schwannomas are located along cranial nerves and may contain cystic-necrotic components. However, nearly complete cystic schwannoma is rare. Nauta et al. classified cystic meningiomas into four types depending on the cavity location [4]. Type I: centrally located intratumoral cyst. Type II: peripherally located intratumoral cyst. Type III: peritumoral cyst surrounded by a glial reaction in the neighbouring parenchyma. Type IV: A peritumoral cyst due to arachnoid evagination between the tumour and the neighbouring parenchyma. The Type I and II cysts are intratumoral and surrounded by meningothelial cells. The Type III and IV cysts are peritumoral and are not surrounded by meningothelial cells. Cystic meningiomas are most frequently located in the cerebral convexity followed by the parasagittal area. The preferred imaging modality or diagnosis is MRI. The Nauta Type I cystic meningiomas appear as a non-enhancing cystic area centrally within an enhancing solid mass. The Nauta Type II cases appear as a solid component peripherally located within a peripherally enhancing cystic mass. Peritumoral cystic meningiomas (Type III and IV) appear T. Ergun E. Torun H. Lakadamyali Departments of Radiology, Alanya Teaching and Medical Research Center, Baskent University, Alanya, Turkey