The Department of Otolaryngology/Head and Neck Surgery

Otology/Neurotology/Skull Base Surgery
Acoustic Neuroma Glossary

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  • ACCESSORY NERVE - see spinal accessory nerve

  • ACOUSTIC NERVE - see cochlear nerve

  • AUDIOLOGY - testing of hearing function; usually divided into two parts: (1) tone recognition, in which the ability to hear high- and low-pitched sounds is quantified, and (2) speech discrimination, in which the ability to recognize spoken sounds is tested. Hearing loss can be quantified in high and low registers, as well as in the ability to recognize spoken words.

  • AUDITORY EVOKED POTENTIAL TESTING - the recording of brain waves elicited by auditory stimuli. When a sound is heard, distinct waves are generated by the cochlea, the cochlear nerve, and the brainstem; these waves can be recorded during an operation to determine whether any additional stress is being placed upon these structures.

  • ACOUSTIC NEUROMA - a benign tumor derived from the schwann cells lining the acoustic nerve (or vestibulocochlear nerve); more accurately known as "vestibular schwannoma" since the tumor is most often derived from schwann cells of the vestibular portion of this nerve. The vestibular nerve is the most common site of schwannoma formation in the entire body; these tumors are also known as "neurinomas" or "nerve sheath tumors."
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  • BRAINSTEM - the lowest section of the brain, connecting the rest of the brain to the spinal cord, also the site at which many of the important nerves controlling structures in the head and face originate; damage to the brainstem may cause coma, paralysis, and problems in a variety of structures.

  • BRAINSTEM AUDITORY EVOKED POTENTIAL TESTING - see auditory evoked potential testing.
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  • CEREBELLOPONTINE ANGLE (CPA) - the area at which the facial and vestibulocochlear nerves traverse from the brainstem to the internal auditory canal; the site at which acoustic neuromas grow and compress the brainstem; the CPA is formed by the borders of the cerebellum, pons, and temporal bone.

  • CEREBELLUM - a structure in the back of the brain important in helping to control coordination. It is attached to the brainstem and may be compressed by an acoustic neuroma; the cerebellum must be retracted in order to perform resection of an acoustic neuroma via the suboccipital approach.

  • CEREBROSPINAL FLUID (CSF) - the fluid created by the brain that then circulates around it, cushioning it and the spinal cord; blockage of flow of CSF anywhere along its usual course of flow may lead to hydrocephalus; the CSF may leak following any operation on the brain, and repair of structures to prevent continued leakage is necessary in order to prevent meningitis.

  • COCHLEAR NERVE - the division of the vestibulocochlear nerve that relays information about sound from the inner ear to the brainstem.

  • COMPUTERIZED TOMOGRAPHY (CT) - an x-ray imaging technique by which a computer is used to analyze x-ray images in order to see the brain or other parts of the body as if cut into slices.

  • CRANIAL NERVE - any one of twelve nerves, which are numbered, originating in the brain or brainstem and conveying information to or from structures in the head, neck, shoulders, or internal organs; the facial nerve is the seventh cranial nerve and the vestibulocochlear nerve is the eighth cranial nerve.

  • CRANIECTOMY - the removal of a portion of skull in order to access the brain in the performance of an operation, the bone of the skull is not replaced.

  • CRANIOPLASTY - repair of a defect of the skull using material from elsewhere; cranioplasty may be done using metal mesh or plates, molded plastic, bone from elsewhere in the body, or other materials.

  • CRANIOTOMY - the removal of a portion of the skull in order to access the brain in the performance of an operation with replacement of the same piece of bone at the end of the operation.

  • CT - see computerized tomography.
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  • EIGHTH CRANIAL NERVE - see vestibulocochlear nerve.

  • ELEVENTH CRANIAL NERVE - see spinal accessory nerve.
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  • FACIAL NERVE - the seventh cranial nerve, controlling motion of the face, the tear glands and taste on the tip of the tongue, as well as several other functions; the facial nerve travels together with the vestibulocochlear nerve in the internal auditory canal and may be compressed or damaged by an acoustic neuroma or an operation.

  • FIFTH CRANIAL NERVE - see trigeminal nerve.
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  • GAMMA KNIFE - a device for performing radiosurgery using radioactive Cobalt sources of irradiation. The patient's head is placed in a frame screwed to the skull using local anesthetic, and radiation is given in a single treatment using several hundred radioactive sources configured in a dome shape and focused on a single point (the tumor).

  • GLOSSOPHARYNGEAL NERVE - the ninth cranial nerve, it controls sensation and the movement of several muscles in the throat; problems with this nerve can lead to swallowing difficulties.
    • H

  • HYDROCEPHALUS - build-up of fluid and pressure in the brain caused by the blockage of flow of cerebrospinal fluid, either in the fluid canals within the brain or at the site of fluid absorption along the veins of the head; hydrocephalus must often be treated by drainage of cerebrospinal fluid to the outside or shunting to another space within the body, such as the abdominal cavity.
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  • INNER EAR - the sensory organs of hearing (cochlea) and balance (vestibular canals) located within the temporal bone.

  • INTERNAL AUDITORY CANAL - the canal extending through the temporal bone between the inside of the skull and the inner ear; the facial and vestibulocochlear nerves are located within this canal, and acoustic neuromas originate in this location.

  • INTRACANALICULAR - within the (internal auditory) canal. A small acoustic neuroma limited to the area within the canal may be called "intracanalicular," or the part of a larger tumor in this area may be called "the intracanalicular portion."
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  • LINEAR ACCELERATOR - a device for performing radiosurgery using a high-powered x-ray tube as the source of irradiation; the patient's head is placed in a frame screwed to the skull using local anesthetic, and radiation is given in a single treatment using a rotating x-ray tube that is moved along several arcs around the patient's head. The x-rays are focused on a single point (the tumor).
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  • MAGNETIC RESONANCE IMAGING (MRI) - type of imaging of the brain or other parts of the body using strong magnetic fields; the imaging machine is able to detect the response of tissues to the magnetic fields and a very detailed image is generated. This is the highest resolution type of imaging of the brain and cranial nerves within the skull, and x-rays are not used.

  • MENINGITIS - infection of the lining of the brain (by bacteria or other organisms); among other causes, may be a complication of surgery or may occur due to leakage of cerebrospinal fluid.

  • MRI - see magnetic resonance imaging.
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  • NERVE SHEATH TUMOR - see schwannoma.

  • NEURINOMA - see schwannoma.

  • NEUROFIBROMATOSIS - a genetic disease which predisposes patients toward brain tumors, along with other problems. Type I neurofibromatosis involves skin abnormalities and numerous types of brain tumors. Type 2 neurofibromatosis (which is much rarer) causes a strong propensity toward acoustic neuromas and several other types of brain tumors early in life. Overall in the population only a small number of acoustic neuromas are caused by neurofibromatosis.

  • NEUROMA - general term for any benign tumor derived from nerve tissue.

  • NINTH CRANIAL NERVE - see glossopharyngeal nerve.
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  • PONS - the middle portion of the brainstem. It also form a border of the cerebellopontine angle. The fifth through the eighth cranial nerves originate from the pons.
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  • RADIOSURGERY - Treatment of abnormalities (usually brain tumors or vascular malformation) using focused radiation. The head is held still using a "stereotactic" headframe, and information from x-ray, CT or MRI images is used to choose a specific target to receive high-dose radiation treatment. The two most popular devices for performing radiosurgery are "linear accelerator" and "gamma knife," also called "stereotactic radiosurgery."
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  • SCHWANN CELL - the cell that creates insulating material of nerves. Acoustic neuromas (or, more properly, vestibular schwannomas) are made up of abnormally growing schwann cells.

  • SCHWANNOMA - benign tumor derived from "schwann cells," or the cells forming the lining and insultation of the nerve; the most common type of schwannoma is the "vestibular schwannoma," also known as "acoustic neuroma."

  • SENSORINEURAL HEARING LOSS - Hearing loss due to injury of the inner ear or cochlear nerve, characterized by inability to hear high-frequency sounds. Acoustic neuromas cause sensorineural hearing loss.

  • SEVENTH CRANIAL NERVE - see facial nerve.

  • SIGMOID SINUS - the large vein that runs within the lining of the brain and drains blood from much of the brain into the jugular vein below the skull. In acoustic neuroma surgery, the sigmoid sinus must be exposed (suboccipital approach goes behind the sigmoid sinus and translabyrinthine approach goes in front of the sigmoid sinus).

  • SPINAL ACCESSORY NERVE - the eleventh cranial nerve; controls motion of neck and shoulder muscles.

  • STEROTACTIC - the use of a frame attached to the head as a frame of reference to allow imaging information (usually CT or MRI) to directly guide treatment to a specific point within the head. Radiation treatment (radiosurgery) or surgery may be stereotactically guided.

  • SUBOCCIPITAL APPROACH - approach used for surgery of acoustic neuromas or other abnormalities. The surgeon goes behind the sigmoid sinus, and the cerebellum must be retracted in order to get to the cerebellopontine angle. The inner ear structures are not disturbed using the suboccipital approach.
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  • TEMPORAL BONE - the bone of the skull at the temple within which are the inner and middle ear structures. The facial and vestibulocochlear nerves travel through canals in the temporal bone, and removal of portions of the temporal bone is necessary for acoustic neuroma surgery.

  • TENTH CRANIAL NERVE - See vagus nerve.

  • TRANSLABYRINTHINE APPROACH - approach used for surgery of acoustic neuromas or other abnormalities. The surgeon goes in front of the sigmoid sinus and through the temporal bone. The inner ear structures are damaged via this approach and hearing is totally lost, but there is no need to retract the cerebellum or any other brain structures.

  • TRIGEMINAL NERVE - the fifth cranial nerve, controlling sensation of the face and the muscles of chewing, along with several other functions. The trigeminal nerve may be involved with large acoustic neuromas.
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  • VAGUS NERVE - the tenth cranial nerve. It controls, among other things, the muscles of the throat, larynx, and esophagus and relays information between the brain and many internal organs. Injury to the vagus nerve may cause problems with swallowing and hoarseness.

  • VESTIBULAR NERVE - the portion of the vestibulocochlear nerve relaying information about balance from the inner ear to the brainstem. There are actually two parts to this nerve, the superior and inferior vestibular nerves, and most acoustic neuromas (more properly called vestibular schwannomas) originate from the superior vestibular nerve.

  • VESTIBULAR SCHWANNOMA - see acoustic neuroma.

  • VESTIBULOCOCHLEAR NERVE - the eighth cranial nerve. It relays information about hearing and balance from the inner ear to the brainstem. There are actually three parts to this nerve - the "cochlear (or auditory) nerve" and two "vestibular nerves." The vestibulocochlear nerve travels within the "internal auditory canal."

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