Diagnosis: Meningioma
Meningioma is the most common extraaxial tumor of the CNS and represents up to 1/5 of all intracranial neoplasms. They occur in women twice as often as men and have a peak incidence of 45 years of age. Meningioma is associated with neurofibromatosis 2. In NF 2 they are often multiple and may occur in children. They are hyperdense on CT and intensely enhance. Most have some surrounding vasogenic edema and up to 1/4 may calcify. 15% may have a cystic component. Hyperostosis of the adjacent bone is present in approximately 1/5. A dural tail is characteristic but not always seen. The additional imaging planes on MR are helpful in characterizing the extraaxial location of meningiomas. On T1, they are typically isointense to gray matter. T2 signal is variable however they are often dark which is helpful in differentiating from an astrocytoma or a metastasis both of which are usually bright on T2. Enhancement with gadolinium is intense and homogeneous unless there is a cystic component. Hemorrhage is unusual in meningioma. The most common location is parasagittal along the falx followed by the convexities and the sphenoid wings. Meningiomas may also be present in the cavernous sinus, the cerebellopontine angle, attached to the optic nerve sheath or intraventricular. The trigone of the lateral ventricle is the most common location for intraventricular meningiomas.
The differential diagnosis of meningioma is straight forward as long as you can be certain the mass is extraaxial or identify a dural tail. A dural based metastasis may mimic meningioma. An ICA aneurysm may also mimic a parasellar meningioma. In this case, it can be seen that the supraclinoid ICA is separate from the mass. Due to the characteristic appearance on this CT scan, this patient was diagnosed with a presumed meningioma and six month follow-up was elected. A prior non-con CT showed that the high attenuation was mostly enhancement with some calcification. Related Cases
