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Meningioma (A Patient Information Service) The term Meningioma is a name for a tumor, arising from cells that form the covering of the brain. The covering layer is called "meninges". The vast majority of these tumors are benign. Meningiomas are generally well defined, discrete lesions, in sizes that vary from a few millimeters, to many centimeters in diameter. Symptoms are caused by compression of brain or spinal cord.Meningiomas account for approximately 15% of all intracranial tumors. They commonly occur in the fourth through sixth decades of life. Meningiomas are a little more common in females and are rare in children (only 1.5% of all Meningiomas occur in childhood). Ninety (90%) percent of Meningiomas are intracranial while ten (10%) percent occur within the spinal canal, most of which are in thorax portion of the spinal column. As with almost all other types of brain tumors, the cause of Meningiomas is unknown. It is generally accepted that these tumors arise from a "misguided" "CAP CELL" which is the embryonic cell of origin that ultimately makes for the development of the "meninges" (the covering of the brain and spinal cord.) Radiation therapy to the brain and/or spinal cord/canal, for some other disease process, has been implicated in subsequent Meningioma formation, especially in children. While trauma is unusual as a cause, there are cases of Meningiomas forming under a fracture, occurring in an area of scarred dura, or around a foreign body. Patients with von Recklinghausen's Disease (Neurofibromatosis), tend to develop multiple Meningiomas at a young age. In these cases chromosomal aberrations are regularly seen. Finally, hormonal factors may play a role in the genesis of Meningiomas; both estrogen and progesterone receptors have been found in Meningioma preparations. The clinical symptoms and signs of Meningiomas are related to those of an intracranial mass lesion, or seizure. The tumor has a predilection for certain regions and produces symptoms and signs specific to the tumor's location. The clinical course of a Meningioma characteristically spans a period of years. CT scanning (done with and without "contrast agent") can be a definitive diagnostic method since it may show the tumor as a homogeneously contrast-enhancing mass with well defined borders. MRI scanning usually accurately identifies the presence of a Meningioma when used with "contrast" enhancement (an agent known as "Gadolinium"). MRI can superbly demonstrate the Meningioma and its relationship to adjacent neural and vascular structures. Finally, catheter angiography is used in some cases, when it is necessary to demonstrate the tumor's vascularity and its blood supply. This may be important in some cases of very vascular tumors where pre-operative embolization, to obstruct the tumor's blood supply, is done to facilitate surgical removal. Meningiomas have variable neurological signs and symptoms, depending on their location, within the nervous system. Convexity Meningioma More than 70% of Convexity Meningiomas (tumors occurring over the top surface of the brain) are in the frontal region. If located in this region, they may remain asymptomatic, while growing to a very large size. Epilepsy and focal neurological signs are common. These Meningiomas have the best potential for total removal.Parasagittal Meningioma These Meningiomas arise in association with the superior saggital sinus (a major draining vein structure of the brain) and are located in the midline. They often cause focal epilepsy, and later, paralysis, especially of the lower extremities.Falcine Meningiomas Tumors arising from the falx (the rigid midline membrane lying between the left and right cerebral hemispheres) are located in the midline and often extend to both sides of the brain. These tumors, while presenting some technical challenges, are very amenable to complete resection.Olfactory Groove Olfactory Groove Meningiomas arise from the cribriform plate which lies under the Frontal Lobe at the base of the anterior portion of the skull. This tumor can grow bilaterally and may become large without causing significant neurological deficits, or evidence of increased intracranial pressure. Loss of smell can often be the only symptom. Changes in mental status are not apparent, until the tumor has reached a large size. Once the tumor becomes large, it impinges on the optic nerves and chiasm, resulting in visual loss.Tuberculum Sellae Meningioma These Meningiomas are also at the base of the skull, lying underneath the Frontal Lobes of the Brain, arise from the planum sphenoidale, tuberculum sellae or the diaphragm sellae (all anatomical structures at the base of the skull beneath the frontal lobes of the brain). They characteristically cause early visual failure which typically involves loss of visual acuity and progressive and asymmetric visual field deficit. Rarely is visual loss sudden.Sphenoid Ridge Meningioma Meningiomas of the sphenoid ridge (a skull bone structure) are traditionally divided into three types: outer, middle, and inner sphenoid ridge tumors. The Outer (or Lateral) Sphenoid Ridge Meningiomas are usually accompanied by epilepsy, focal weakness, and trouble with language function, when present on the left side. The tumors of the inner (or Medial) sphenoid ridge usually compress the optic nerve and present with early unilateral visual loss. They also may involve the cavernous sinus to cause double vision and numbness of the face.Posterior Cranial Fossa Meningioma These constitute about 10% of all Meningiomas. The neurological findings in these tumors can be a combination of posterior cranial fossa and supratentorial symptoms. These can be headache, speech disturbance, visual changes, nausea/vomiting, and balance difficulties. These tumors can also cause extensive cranial nerve findings, including facial weakness, hearing loss, swallowing difficulty, and facial numbness. Depending on the specific location of the tumor they may cause weakness and spasticity. Some of these symptoms may mimic the usual symptoms seen with Acoustic Neuromas, Epidermoid Tumors or Arachnoid Cysts.TREATMENT The treatment options include observation, surgery and radiation. Small tumors in older patients that do not cause symptoms can be followed with yearly MRI scans. Since these tumors are benign and slow growing, they may not cause any problems during the life span of some patients.Surgery However, in young patients, in critical locations, and when these tumors cause symptoms (including seizures), surgical removal is the best treatment option. Meningiomas are generally thought to be slow growing and benign, and every effort is aimed at total removal. Certain tumors, however, present a formidable technical challenge because they adhere to vital neural and vascular structures at the base of the brain. This is an area of Neurosurgical Special Interest called SKULL BASE TUMOR SURGERY which requires a dedicated multi-disciplinary team of specialists such as a Skull Base/Microvascular Neurosurgeon, Craniofacial Plastic Surgery, Neuro-otologic Surgeon, Surgical Neuro-ophthalmology among others. In addition, MINIMALLY INVASIVE MICROENDOSCOPIC NEUROSURGICAL TECHNIQUES may be applicable for some of these tumors.Radiation Therapy Radiation therapy is an option for some patients with recurrent skull base tumors, or in patients who are considered to be very poor risks for surgery (or in the very unusual case of a tumor, in an area where surgery is very likely to produce disastrous consequences). Radiation is best given as stereotactic radiosurgery.Finally, hormonal therapy with anti-estrogen agents is a possible alternative. The long term results and effects of these agents remain to be determined. Tumor Recurrence Meningiomas are known to recur. Many factors relate to recurrence, the most important of which, is the extent of the original removal. Complete resection, including removal of the dural margin, is associated with a low rate of recurrence. Of course, Meningiomas that are more aggressive (or the rare metastatic Meningiomas), are associated with an increased rate of recurrence based on the biology of their cellular components.
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All content ©2024 by Neurosurgical Consultants, P.A. Author, Martin L. Lazar, MD, FACS All Rights Reserved. See Usage Notices. |