Meningioma without dural attachment: case report, classification, and review of the literature.

ABSTRACT

BACKGROUND: The primary occurrences of meningiomas without attachment to the dura are rare. Clinical considerations and pathophysiologic mechanisms about these tumors have not been sufficiently explored, and a complete classification has not been accomplished. CASE DESCRIPTION A 16-year-old adolescent boy presented with epileptic seizure for 9 years. Neurologic deficits were not found on admission. Magnetic resonance imaging revealed a 25 x 23-mm mass lesion without dural attachment located in the parietooccipital region. The tumor was iso-intense on T1-weighted and hyperintense on T2-weighted images, and became clearly and heterogenously enhanced with gadolinium. During surgery, a right parietooccipital craniotomy revealed the tumor was completely buried in the sulcus occipitalis anterior. Total removal of the tumor was accomplished. Histologic examination indicated that the lesion was an atypical meningioma. CONCLUSION: According to sites of the tumor, supratentorial meningiomas without dural attachment are classified into 5 varieties, and posterior fossa meningiomas without dural attachment into 4 categories. Except for intraventricular ones, meningiomas without dural attachment predominantly occur in males. The average age is about 20 years younger than that of meningiomas in general. Fibroblastic meningiomas constitute the major subtype. Intraparenchymal or subcortical meningiomas should be considered as one type, which may arise from arachnoid cells of the pia mater within brain sulcus.