A rare spontaneous temporal meningoencephalocele with dehiscence into the pterygoid fossa.

We present an extremely rare case of basal meningoencephalocele that protruded into the left pterygoid fossa from the middle cranial fossa. After a 30-year-old woman experienced a generalized tonic-clonic seizure, computed tomography (CT) scanning showed a large bone defect of the left middle cranial base. A mass lesion with low signal intensity on T1- and high signal intensity on T2-weighted magnetic resonance imaging (MRI) was visualized in the left pterygoid fossa. A biopsy was performed through the transantral approach. Because cerebrospinal fluid (CSF) was observed to flow from the mass lesion, it was diagnosed as a meningoencephalocele. CT showed bone defects in the skull base and a well-circumscribed expansile mass lesion. MRI demonstrated that the brain parenchyma extended into a CSF-filled meningocele. These findings demonstrate that CT and MRI provide adequate information for the diagnosis of meningoencephaloceles.