Meningiomas are the most common benign brain tumor although up to 10% can exhibit more aggressive growth patterns. Meningiomas are classified by the World Health Organization into 3 grades based on their growth pattern and histology: Grade I (typical – 90%), Grade II (atypical – 6-9%) and Grade III (anaplastic 1-3%). These tumors arise from arachnoidal cap cells in the brain coverings (meninges). They are more common in women than men and can occur in all ages but are typically seen in middle-aged and older adults. They may arise from any meningeal surface and are typically attached to the dura (outer layer of the meninges) but can also occur in the cerebral ventricles. Common locations include the convexity of the calvarium, frontal fossa (olfactory groove), tuberculum sella, sphenoid wing and the area around the jugular foramen in the posterior fossa.
Meningiomas may produce a variety of symptoms depending upon their location.
Meningiomas that arise in the midline from the area above and in front of the pituitary gland and sella (the tuberculum sella and planum sphenoidale), typically cause progressive visual loss from optic nerve and chiasm compression. They may also cause headache, double vision and loss of pituitary function.
Meningiomas that arise in the midline under the frontal lobe in the area called the olfactory groove typically cause headache, seizures and/or personality changes.
Meningiomas that arise over the surface of the frontal, temporal, parietal or occipital lobes may cause a variety of symptoms including headache, seizures, visual loss, double vision, weakness, fatigue, difficulty walking, confusion and personality changes.
Meningiomas that arise in the posterior fossa along the side of the cerebellum or brainstem (so-called petro-clival meningiomas) or at the skull base where the spinal cord begins, may cause difficulty walking, in-coordination, numbness, hearing loss, double vision, difficulty swallowing, urinary incontinence, headache and neck pain.
Meningiomas are best diagnosed by an MRI of the brain with gadolinium, or by a CT scan of the brain with contrast. Depending upon the location, a focused MRI of the pituitary region, temporal bones, internal auditory canals or orbits may be indicated to obtain better anatomical detail of a meningioma. Other tests may also be needed such as angiography (a CT angiogram or an MR angiogram), visual field tests, an audiogram or hormonal tests.
Symptomatic meningiomas are typically treated by surgical removal. The approach used depends upon the tumor location and may include a craniotomy (convexity, temporal, supra-orbital or retro-mastoid) or an endonasal transsphenoidal tumor removal. Minimally Invasive Removal of many meningiomas is now possible either by an Endonasal Route, Supraorbital (Eyebrow) Craniotomy or Retromastoid Craniotomy or the route.
The advantage of the endonasal approach over a transcranial approach is that brain retraction is not necessary and manipulation of the optic nerves and chiasm is minimized. However, for larger tumors (over 3 or 4 cms) or those that extend far off the midline, the supraorbital eyebrow craniotomy is an excellent minimally invasive approach. With either approach, vision typically improves and pituitary hormonal function is usually preserved.
Meningiomas cannot be completely removed in up to 20-25% of cases. With incomplete removal or if a tumor re-grows stereotactic radiotherapy (SRT) or Stereotactic Radiosurgery (SRS), are often needed to halt further tumor growth. The tumor control rate with SRS or SRT is quite high with over 90% of patients having no further tumor growth. Complications of SRS or SRT such as visual loss or brain injury are rare.