Sylvian meningioma without dural attachment in an adult.

This paper presents a rare case of a sylvian meningioma in a 35-year-old male. The patient visited our hospital because of a 10-year history of simple partial seizures. Magnetic resonance imaging revealed a 3.5-cm, well-circumscribed, homogenously enhanced, circular mass without dural attachments in the left insular region. The tumor was not stained on angiogram. The tumor was located in the extra-axial space of the sylvian fissure without any dural attachment, and was strongly attached to the middle cerebral artery. The tumor was excised, and a histological diagnosis of a transitional meningioma without a malignancy was made. A Sylvian meningioma without dural attachment is quite rare, and a preoperative differentiation of this lesion is generally difficult. This paper discusses the characteristics and possible pathogenesis of meningiomas without a dural detachment.