General Principles

The Department of Otolaryngology/Head and Neck Surgery

Otology/Neurotology/Skull Base Surgery

General Principles of Acoustic Neuroma Treatment

(information regarding Microsurgery, Serial MRI scans, and Radiosurgery.)

We prefer an individualized treatment strategy for the treatment of acoustic neuromas. When a patient is diagnosed with an acoustic neuroma, there are three possible options for treatment: (1) microsurgical removal of the tumor; (2) watchful waiting; and (3) radiation therapy.

The best course of treatment is determined only after consultation with all key members of the acoustic neuroma treatment team and after detailed discussion with the patient and his or her family.

The goals of treatment are as follows:

The total removal of tumor, or the prevention of tumor growth.
Normal facial nerve function.
Preservation of hearing whenver possible.

The Treatment Options

Microsurgery - At the current time, we feel that microsurgical excision of acoustic neuromas is the best way to meet the goals listed above for most patients. The National Institute of Health feels microsurgical removal is the treatment of choice. With the use of the operating microscope and modern surgical techniques, the risk to the facial nerve and the chance of preserving hearing are both superior to radiosurgery. With microsurgery, the entire tumor can be removed, thus effecting a cure. Radiation treatment retards growth but does not cure.

We use several operative approaches to acoustic neuromas depending upon the size of the tumor and the amount of hearing present preoperatively:

The suboccipital approach is used for patients with good hearing since the auditory organs are preserved. It is also used for some larger tumors since the area of access to the tumor is greatest. This approach involves going along the side of the cerebellum to reach the tumor. The advantages of this approach are the large area seen and the preservation of the inner-ear structures in order to preserve hearing.
The translabyrinthine approach is used for most patients who already have absent or very poor hearing at the time they are first seen. This approach involves going through the temporal bone and the inner ear, to expose the tumor and nerves without the need to directly expose and retract the cerebellum. The advantage of this approach is that the brain is not manipulated and that the facial nerve may be easier to identify. The disadvantage is that hearing must be sacrificed using this approach.
The middle fossa approach is sometimes used as one of the approaches when attempting to preserve hearing.
Combined approaches may be used for especially large or difficult tumors. These are individualized for each case and utilize our extensive experience using a large variety of approaches to the skull base.

We use a number of technological aids and monitoring devices while performing these procedures, including the following:

Operating Microscope: The operating microscope allows magnification and improved lighting for the procedure. It is standard of care at all centers performing these operations.

Facial Nerve Monitoring: Using electrodes attached to the face muscles, we are able to fully monitor the functioning of the facial nerve throughout the operation. The facial nerve monitor is able to detect any manipulation of the nerve, and, using a nerve stimulator, we are able to search for the nerve and identify it prior to performing tumor removal. Due to pressure created by the tumor, the facial nerve may be distorted and flattened, making visual identification of it difficult. We use facial nerve monitoring for all patients undergoing operation for acoustic neuroma. Pioneering research concerning the use of the facial nerve monitor has been carried out by Drs. McMenomey and Delashaw.

Auditory Evoked Potential Monitoring: (ABR monitoring) During surgery, we are able to monitor hearing in all patients with good preoperative hearing. A small earphone is used to make clicking sounds and the brainwaves created as this signal is carried along the auditory nerve to the brainstem are recorded. In this way, we can detect any manipulation of the auditory nerve. This type of monitoring is used in all patients in whom we are attempting to preserve hearing, and its use has been helpful in successfully preserving hearing.

Operating Laser: We use a KTP laser to vaporize tumor cells in a manner that requires only minimal manipulation of tissue. It is especially useful for removing tumor close to the nerves.

Ultrasonic Aspirator: The ultrasonic aspirator uses high-frequency sound waves to remove the tumor. We use this device to more quickly and safely resect the tumor, especially with larger tumors.
Using the above techniques, the facial nerve can be anatomically preserved over 99% of the time. While temporary facial weakness may be a problem, over 90% of patients are left with normal facial function or only mild weakness after a period of recovery. The risk to the facial nerve is proportional to the size of the tumor, so that the odds for patients with small tumors are actually much better than this. Preservation of useful hearing is an obtainable goal in selected patients.
Of course, operative treatment has additional risks, which are small but possible. These risks are thoroughly discussed with patients and their families at the time of consultation.
Following with Serial MRI Scans - Although slow-growing, acoustic neuromas generally continue to grow. Since treatment of small acoustic neuromas has a better prognosis than treatment of larger ones, the option of waiting and following is usually not preferred for most patients. There are, however, several exceptions to this:

Elderly patients: Patients who are diagnosed after age 75 or 80 may be more likely to have slower-growing tumors (that have taken a very long time to show up in the first place). Therefore, the best course of action may be to simply follow the tumor to be certain that it is growing at a pace that is unlikely to cause problems during the patient's lifetime.
Patient with very small tumors who are reluctant to proceed with surgery: Patients with very small tumors can be followed in order to prove that the tumor is growing. A scan after a 6-month or 1-year interval is likely to show tumor growth, and additional treatment can be planned at that time. This option can be done with the understanding that treatment of a larger tumor is less desirable.
Patients with other serious medical problems: Often these patients are at more risk with a surgical option and thus following these with serial scans is appropriate.

Radiosurgery - Radiosurgery is a form of local radiation that has recently been used to treat acoustic neuromas. This treatment is generally reserved for patients unable to undergo surgery. Radiation is generally held in reserve as results with microsurgical techniques for facial function and hearing are superior to radiation.
We would recommend radiosurgery for patients with other medical problems that would increase the risk for surgery, for elderly patients, or for patients adverse to undergoing an operation.
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