Treatment Options for Acoustic Neuroma

The obvious goal of treatment of any benign brain tumor is to eradicate the tumor while preserving neurologic function. There are many factors which come to bear in terms of the success of treatment for these tumors. Acoustic neuromas, because of their location in proximity to delicate brain structures and cranial nerves, are a complicated treatment problem.

The treatment of these tumors is best left in the hands of professionals who have a significant and on-going experience with their treatment. An acoustic neuroma is one of a small number of brain tumors that, in order to obtain the best outcome, surgeons who frequently treat this problem must direct the patient's care. Experience in dealing with all aspects of treatment is important in order to maximize success and take advantage of all therapeutic options.

There are three treatment options available to a patient.These options are 1) Observation; 2) Microsurgical Removal; and 3) Radiation (“radiosurgery” or “radiotherapy”).

Choosing the best option is a decision that must be made by the patient and physician after careful review of the patient’s age, physical health, tumor size and location.  The skill and experience of the treating physician are also factors to be considered, and an open discussion should occur.

Observation:

Acoustic neuromas may be discovered incidentally in the course of evaluating another problem, or when the tumor is very small and there are few symptoms.  Since acoustic neuromas are benign tumors and produce symptoms by pressure on surrounding nerves, careful observation over a period of time may be appropriate for some patients.  When a small tumor is discovered in an older patient, observation to determine the growth rate of the tumor may be indicated if serious symptoms are not present.  If it appears that the tumor will not need to be treated during the patient’s normal life expectancy, treatment and its potential complications may be avoided.  In this case, MRI’s are performed periodically, and if the tumor does not show significant growth, observation is continued.  On the other hand, if the tumor shows progressive increase in size, treatment may become necessary.

Another group of patients for whom observation is indicated includes patients with a tumor in their only hearing or better hearing ear, particularly when the tumor is of a size that hearing preservation with removal would be unlikely.  In this group of patients, MRI is used to follow the growth pattern.  Treatment is recommended if either the hearing is lost or the tumor size becomes life threatening, thus allowing the patient to retain hearing for as long as possible.

Source :

 

-          Web Site- www.hei.org  

- Web Site – www.anausa.org

Microsurgical Tumor Removal

 

A - Partial Tumor Removal:

Partial removal of an acoustic neuroma may be indicated in some patients in order to reduce the risk of complications, with the realization that further surgery may be needed in the future.  Older patients with large tumors causing a threat to life may elect to have their surgeon subtotally remove their tumor.  Partial tumor removal has also been advocated in some patients who have large tumors in their only hearing ear.  This surgical management will reduce the tumor in size, so that it may cause no threat to the patient’s health during his or her life expectancy.  This approach may greatly reduce the probability of any facial nerve dysfunction as a result of the surgery, but there is still a risk for hearing loss with partial removal.  Periodic MRI studies are important to follow the potential growth rate of residual tumor.

B - Total Tumor Removal:

Many tumors can be entirely removed by surgery.   Microsurgical technique and instruments, along with the operating microscope, have reduced the surgical risks of total tumor removal.  Preservation of the facial nerve is the primary task for the experienced acoustic neuroma surgeon to prevent permanent facial paralysis.  Preservation of hearing in the affected ear is also an important goal in patients who present with functional hearing.

Facial nerve function is electrically monitored during surgery.  This is a valuable aid for the surgeon while the tumor is being removed from the facial nerve during surgery.  Cochlear nerve electrical monitoring is also employed during operations when preservation of hearing is a goal.

There are several surgical approaches used for removal of acoustic neuromas.  The approach is based on several factors such as tumor size, location, skill and experience of the surgeon, and whether or not hearing preservation is a goal.

C - Surgical Approaches

The choice of surgical approach depends upon the size of the tumor and the level of residual hearing detected on the audiogram. Again, the larger the tumor the lower the chances of saving hearing. The three most common surgical approaches for acoustic neuromas are the translabyrinthine, middle fossa and retrosigmoid approach. All of these procedures are performed under general anesthesia. Patients in general spend 5 days in the hospital, including the day of surgery.

Middle Fossa Approach

This approach is used for small tumors and is utilized in cases when hearing is to be conserved. An incision is made beginning just in front of the ear and extends upward in a curved fashion. A small opening in the bone is made above the ear, and the membrane that covers the brain is elevated away from the bone and gently held away from the bony floor of the skull. Bone is then removed over the top of the internal auditory canal to expose the tumor. Tumor removal is complete in the vast majority of cases. Every effort is made to preserve hearing and still completely remove the tumor.

The middle fossa approach is a treatment that House Ear Clinic surgeons developed and currently utilize more than any other center in the world.

The surgeon and the patient should thoroughly discuss the reasons for a selected approach.  Each of the surgical approaches has advantages and disadvantages, and excellent results have been achieved using any of the above approaches.

Translabyrinthine Approach

The translabyrinthine approach may be preferred by the surgical team when the patient has no useful hearing, or when an attempt to preserve hearing would be impractical.  The incision for this approach is located behind the ear.  It involves removing the mastoid bone and some bone in the inner ear, allowing excellent exposure of the internal auditory canal and tumor site.  This approach facilitates the identification of the facial nerve in the temporal bone prior to any removal of the tumor.  The surgeon, therefore, has the advantage of knowing the location of the facial nerve prior to tumor dissection and removal.

Retrosigmoid/Sub-occipital Approach

An incision is made behind the ear and an opening in the skull is made behind the mastoid bone. The portion of the brain called the cerebellum is retracted away in order to expose the tumor.The surgeon observes the tumor from its posterior surface, thereby seeing the tumor in relation to the brainstem.  When removing large tumors through this approach, the facial nerve can be exposed by early opening of the internal auditory canal.  Small tumors can be removed with hope of preserving hearing in some patients through this approach.

In most cases the tumor can be completely removed. Every effort is made in this approach to preserve hearing and still completely remove the acoustic neuroma. In some cases, because of invasion of the auditory nerve by the tumor, it is necessary to sacrifice hearing in order to completely remove the neuroma. The success of hearing preservation in these cases is largely dependent upon the size of the tumor and the condition of the auditory nerve in relation to the tumor.

Source :

 

-          Web Site- www.hei.org  

- Web Site – www.anausa.org

 

Radiosurgery

Stereotactic radiation therapy, referred to as “radiosurgery” or “radiotherapy”, is a technique based on the principle that radiation delivered precisely to the tumor will arrest its growth while minimizing injury to surrounding nerves and brain tissue.  This non-invasive procedure can be performed in a one-dose treatment on an outpatient basis, or in a multi-dose treatment ranging from several days to over several weeks.

In single dose treatments, many hundreds of small beams of radiation are aimed at the acoustic neuroma.  This results in a high dose of radiation to the tumor and very little to any surrounding brain structures. Radiosurgery is delivered as a one-time, outpatient treatment.  Many patients have been treated this way with high success rates.  Facial weakness or numbness, in the hands of experienced radiosurgeons, occurs in only a small percent of cases and is usually temporary.  Hearing can be preserved in many cases.

The multi-dose treatment, fractionated stereotactic radiosurgery (FSR), delivers smaller doses of radiation over a period of time, requiring the patient to return to the treatment location on a daily basis, sometimes over several weeks.  Each visit only takes a few minutes and most patients are free to go about their daily business before and after each treatment session.  FSR may become a more effective treatment as greater experience is gained with this technique.

Obvious advantages of radiosurgery are its non-invasive nature, its shortened immediate recovery time, its preservation of hearing in many cases, and its value as an alternative for patients unable or unwilling to undergo surgery. On the other hand, radiosurgery is limited to small or medium tumors. The long-term results for radiosurgery in its present form are not available, and the potential for yet undiscovered problems may exist.  The patient should be aware that radiosurgical treatment is a means to seek to control the tumor’s growth without removing it.

The source of radiation used in radiosurgery is either radioactive cobalt or a linear accelerator. The radiation is called a gamma ray when it comes from a cobalt source (such as the gamma knife) and an x-ray when is comes from a linear accelerator (LINAC). Both devices can equally produce the desired therapeutic radiation. The treatment team usually consists of surgeon, radiophysicist, and a radiation oncologist working together to develop a treatment plan based on the size and shape of the tumor.  Their experience and expertise is far more important than the machine producing the radiation.
 

Picture 1 – LINAC

Picture 2 – Gamma Knife
 

Source :

- Web Site – www.anausa.org

ACOUSTIC NEUROMA

Treatment Options
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