Meningiomas, which comprise about a third of tumors that originate in the brain, are so called because they grow from the meninges, the membranes that protect the brain and spinal cord. A fossa meningioma grows in or around a hollow area, or fossa, between bones of the skull. Most notable are the three cranial fossae at the base of the brain that accommodate the lobes: the anterior fossa at the front; the middle fossa, also known as the sides of the base; and the posterior fossa, on the underside of the brain at the back. A tumor also can occupy one of many lesser fossae, hence a possible diagnosis of meningioma involving the jugular fossa, pituitary fossa, temporal or infratemporal fossa, pterygopalatine fossa or supraclavicular fossa. The development of meningiomas is unpredictable, and while not common, it is possible for a tumor to affect more than one fossa.
As for the less-prominent sites for meningiomas, the jugular fossa is located in the jugular notch, at the base of the throat. Housing the pituitary gland, the pituitary fossa is a small pocket inside the sphenoid bone, which itself straddles the middle cranial fossa. The temporal fossae, where the jaw muscles are located, are at the sides of the skull, just above and behind the infratemporal fossae. The pterygopalatine fossa lies behind the upper jaw. Farther from the brain, the supraclavicular fossae are above the clavicle bones, which connect the breast bone to the shoulders.
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A fossa meningioma may be categorized further based on its point of origin. Often that is not in the fossa at all but rather in adjacent tissues, spaces or bones. Among the many possibilities, a tumor growing into one of the three main fossae might carry an additional label such as sphenoid wing, parasagittal, suprasellar, petrous, foramen magnum, tentorial or clival meningioma to designate its precise origin.
The impact of a fossa meningioma on an individual’s health depends on the tumor’s pattern — its rate of growth, direction of growth and whether it has grown through or around bone. Fossa meningiomas, which occur primarily in older adults, are almost always benign, with possibly more than half of them asymptomatic. Serious symptoms can occur, however, when these tumors grow large enough to put pressure on adjacent parts of the brain that control the central nervous system, the senses or critical bodily functions.
A meningioma that develops in the anterior fossa can impair the senses of smell and vision or compromise pituitary activity. A middle fossa meningioma can affect eye movements and facial sensations or put dangerous pressure on the internal carotid artery, which supplies blood to the brain. The deepest and largest of the three cranial fossae, the posterior fossa, is particularly critical in that it houses the brain stem and the cerebellum, which control all organ and mental activities. A tumor growing in this area can cause problems with breathing, swallowing and speaking, damage the senses of hearing or taste or impair balance and coordination.
The most effective remedy for a symptomatic fossa meningioma is to remove it surgically, along with the immediately adjacent brain tissue or bone. If the edges of the tumor are well defined, removal can be relatively simple. As with other kinds of tumors, however, a fossa meningioma can be complex and less defined, growing in and around bones of the skull, requiring a more intricate operation. The preferred course of treatment for an asymptomatic meningioma is to leave the tumor alone and monitor its activity, if any.