LAUSR

A 45-year-old woman was referred to our hospital with the complaints of dizziness, blurring vision and subsequent syncope. Diffusion and conventional magnetic resonance imaging (MRI) were performed to the patient. The patient’s MRI showed an extra-axial mass of 4 9 2.5 cm in size in the left frontoparietal region. The mass was starting from centrum semiovale level and continuing through the vertex. The mass was hypointense on T1-weighted (W) images, hyperintense on T2W images containing pointwise hypointense areas. It was having microcystic components and minimal peritumoral edema (Fig. 1). After contrast injection, central mild enhancement with reticular appearance and peripheral thin enhancement was revealed (Fig. 2). Diffusion-weighted (DW) imaging showed increased diffusion (Fig. 3). Pathological examination of totally excised lesion was reported as microcystic meningioma. Meningiomas are common intracranial tumors. However, as a very rare subtype of meningiomas, microcystic meningiomas constitute for 1.6% of all intracranial meningioma cases. Typical, atypical or anaplastic meningiomas should be regarded in differential diagnosis of microcystic meningiomas. Computed tomography (CT), conventional MRI, DW images and ADC maps are useful in diagnosis and differential diagnosis of microcystic meningiomas. Typically meningiomas are defined as extraaxially located lesions, having dural tail, and showing strongly homogeneous contrast enhancement without edema around brain parenchyma. The microcystic meningiomas are reported as low-density lesions at CT examinations. They usually show high-contrast enhancement. Half of the cases may show hyperostosis. Microcystic meningiomas are reported as hypointense on T1W images, and as hyperintense on T2W images of MRI and very often they show signal intensity compatible with peritumoral edema. The serious peritumoral edema findings are more frequent and more characteristic MRI findings of microcystic meningiomas compared with the classical meningiomas [1, 2]. However, in the recent studies, more aggressive atypical and anaplastic meningiomas were reported to have similar findings. In the study of Avetis et al. [3], ADC maps were shown to be more effective in differentiation of microcystic meningiomas from more aggressive atypical or anaplastic meningiomas. Tumors with high grade and cellularity show significantly lower ADC values compared with normal brain tissue. In addition, Terada et al. [4] described that a reticular appearance on gadolinium-enhanced T1-weighted MRI and DW imaging and relatively low ADC values might be the diagnostic markers of microcystic meningiomas. These findings are important for the accurate diagnosis and surgery planning. In conclusion, microcystic meningiomas must be kept in mind in the differential diagnosis of extra-axially located tumors showing contrast enhancement with reticular appearance, containing pointwise hypointense areas at T2W images and displaying increased diffusion with peritumoral edema. & Mustafa Koplay [email protected]