The skull is divided into the anterior, middle and posterior fossa. The base of the skull in the anterior fossa has the olfactory nerves that pass to the nose for the sense of smell. The junction of the middle fossa and the anterior fossa has the carotid arteries entering the brain, the cavernous sinuses draining blood back to the heart and multiple cranial nerves supplying the vision, movement of the eyes and sensation of the face. The posterior fossa has the remaining cranial nerves passing through the skull. They supply hearing, balance, facial movement, swallowing, the vocal cords, the tongue and the trapezius muscle. Also nerves pass through that influence the heart, lungs and gastrointestinal tract. The major arteries that supply the posterior fossa are also immediately adjacent to the skull. These include the vertebral and basilar arteries. Tumors that arise along the skull base can damage or destroy any of these structures. They may also damage or destroy the skull and the dura. Cerebrospinal fluid leaks may develop. They may be malignant or benign tumors. In addition, pituitary gland tumors grown in the skull base in their own compartment called the pituitary fossa. They can affect a vast array of metabolic activities, sexual activities and growth. The optic nerves may become damaged.
Causes of Skull Based Tumors
The majority of skull based tumors are benign. They include meningiomas, that are tumors arising from linings of the brain. Acoustic neuromas are also common. They usually develop from the vestibular nerves. Their earliest symptom is usually hearing loss, especially in a crowded room. Pituitary tumors are quite common. Often they remain asymptomatic. They may produce hormones. These can interfere with fertility, growth and metabolism. Chordomas are rare tumors that arise from the notochord or fetal remnant. They occur along the base of the posterior fossa. Other malignant tumors that affect the skull base include metastatic cancer and lesions that directly spread from such areas as the nasal cavity. The latter included tumors such as nasopharyngeal carcinoma. Tumors of the sinuses or mucoceles, which are localized cysts enlargements of the linings of the sinuses, may enlarge and destroy a portion of the skull base.
Signs and Symptoms of Skull Based Tumors
The symptoms that occur depend on where the tumor arises. This will dictate which components of the central nervous system will be affected. The rapidly with which the tumor enlarges is also of great significance. Rapidly growing tumors are much more likely to produce symptoms that slowly growing benign tumors. The latter may grow to enormous size before symptoms become apparent. Symptoms may also occur from a generalized increased in pressure within the skull. Tumors of the anterior fossa produce loss of smell, change in personality, problems with memory, problems with controlling urination and sometimes behavioral problems. Middle fossa tumors can produce seizures, they can affect vision and produce double vision. Posterior fossa tumors can produce problems with balance, incoordination, loss of facial movement, loss of hearing, dizziness and vertigo. Occasionally, weakness or atrophy of the tongue may occur. Swallowing problems may develop. All these tumors can produce headache and at times nausea and vomiting. They can all produce increased intracranial pressure which can also compromise vision. Some of them, particularly those of the posterior fossa, can produce hydrocephalus. Here, spinal fluid which is constantly formed and circulated through the brain begins to accumulate. There can be severe headache, nausea, vomiting, coma and death.
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Medical Content Last Updated on 07/12/2008
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