Skull Base Surgery

What is the skull base?

Skull base is the term used to describe the area of the skull that provides the base on which the brain rests. Contained within the skull base are the eye orbits, ear canals, two carotid arteries, two vertebral arteries, 12 cranial nerves and the blood drainage system of the brain. These many intricate structures make the skull base one of the most complex areas on which to operate.

What are the cranial nerves and why are they so important?

There are 12 pairs of cranial nerves. Each pair of nerves is responsible for a specific, basic function such as blinking, swallowing or focusing the eyes. One of each pair of cranial nerves provides feeling and function or innervates, the right side of the body and the other nerve in the pair innervates the left. Many tumors of the skull base can affect the cranial nerves, both by their presence and by the steps the surgeon must take to remove the tumor. The result may be a permanent or temporary loss of function of one or more of the cranial nerves. Dr. Klotch will be able to discuss your specific situation with you as well as your risks of damage to the cranial nerves.

First Cranial Nerve (olfactory nerve) - this nerve is responsible for smell. If injured by tumor or surgery for tumor removal, food taste is also altered.

Second Cranial Nerve (optic nerve)- this nerve is responsible for vision. A partial injury to this nerve may result of partial vision loss.

Third, forth, and sixth Cranial Nerves (oculomotor, trochlear, and abducens) - these nerves are used to control movement of the eyeball. Injury can cause double vision. The third also controls pupil dilation.

Fifth Cranial Nerve (trigeminal nerve) - this nerve controls both function and sensation of the face and if damaged can result in difficulty chewing and diminished facial sensation or facial numbness.

Seventh Cranial Nerve (facial nerve) - this nerve controls facial movements. An injury can result in a facial droop.

Eight Cranial Nerve (auditory or acoustic nerve) - this nerve is responsible for hearing. Skull-base surgery can sometimes leave hearing intact once a tumor on this nerve is removed.

Ninth Cranial Nerve(glossopharyngeal) - this nerve is responsible for sensation to the back of the throat.

Tenth Cranial Nerve (vagus nerve) - this nerve protects against choking and allows for normal swallowing and speech.

Eleventh Cranial Nerve (spinal accessory nerve) - this nerve responsible for shrugging shoulders.

Twelfth Cranial Nerve (hypoglossal nerve) - this nerve is responsible for tongue movement.

Which types of diseases are treated with skull base surgery?

A variety of benign tumors are treated with skull base surgery. These include acoustic neuroma, meningioma, schwannoma, glomus jugulare and vagale, epidermoid, pituitary tumors and many others. Malignant tumors managed with skull base surgery include squamous cell carcinoma, esthesioneuroblastoma, chondrosarcoma, chordoma, and endolymphatic sac tumors. Skull base surgical techniques are also sometimes employed to repair fractures of the skull base, to treat cerebral aneurysms, as well as to remove deep-seated infections of the skull base bone.

What is skull base surgery?

The basic concept of skull base surgery is to approach the tumor from underneath or from the side by removing specific areas of the skull base bone. Thus, the tumor can be exposed with little to no brain retraction.

What type of symptoms do patients with skull base tumors have?

Tumors arising within the skull base are rare and usually cause few symptoms until they grow to a size where they begin to affect neurologic function. These symptoms may manifest as double vision, facial pain or twitching, hearing loss, loss of balance or dizziness, hoarseness or tongue weakness. Occasionally, an asymptomatic tumor may be diagnosed when a middle ear mass is noted during routine examination of the ears.

How is a skull base tumor diagnosed?

An MRI of the brain and/or skull base with and without gadolinium contrast is extremely sensitive at diagnosing these rare tumors with little risk to the patient. A CT scan of the skull base or temporal bone may also be needed to evaluate the condition of the surrounding skull base bone. Occasionally, a MRA or MRV are useful to study how the blood vessels to the brain are affected by the tumor. For large or very vascular tumors, an angiogram with embolization may be performed prior to surgical resection in order to plug the arteries that feed the tumor. This reduces blood loss during surgery.