|
|
|
|
|
 |
Acoustic
Neuroma PATIENT
INFORMATION |
|
|
|
Acoustic neuromas are benign growths that occur on the 8th cranial nerve. This nerve is divided into three parts. The hearing part, called the cochlear nerve, travels from the brain through the internal ear canal into the cochlea, or hearing portion of the inner ear. There are two balance nerves known as vestibular nerves, which also travel along with the hearing nerve from the brain through the internal ear canal to the balance portion of the inner ear. The acoustic neuroma arises from the covering of one of the two vestibular nerves. These tumors grow slowly, usually one tenth of an inch each year. As they grow, they will first cause some
hearing loss and ringing in the ear, or
tinnitus. This can be very mild or it can be sudden and severe. There are usually no other symptoms from these growths until the tumor gets fairly large. As the tumor gets larger, it presses against the 5th cranial nerve, or the trigeminal nerve. This nerve provides sensation to the face. If the tumor gets very large, it will grow into the brain and eventually cause some imbalance and headaches with blurred vision. If the tumor is allowed to grow to a giant size, it eventually causes death due to pressure on the brain. Fortunately, this rarely happens in the present day due to our methods to detect these tumors earlier.
(Diagram D)
Because these tumors can get very large without causing many symptoms, it is important to have a high index of suspicion regarding these tumors in the case of asymmetric hearing loss. The gold standard test to identify these tumors is an MRI scan. The MRI scan can identify even tiny tumors. Other tests that are useful in identifying the tumor and telling more about the tumor are brain stem audiometry and electronystagmography. These tests measure the integrity of the hearing and balance nerves.
Treatment of these tumors depends a lot on the size of the tumor, the hearing that remains, and the general health of the individual. The small tumors, those confined to the internal ear canal or internal auditory canal, are found with increasing frequency due to advantages of the MRI scan. A medium sized tumor is classified as one that has extended beyond the internal ear canal or internal auditory canal (IAC) and into the space between the ear bone or temporal bone and the brain. This space is filled with a fluid called cerebrospinal fluid. The medium sized tumors extend into the spinal fluid but not into the brain. Large tumors are those that extend from the internal auditory canal through the spinal fluid and into the brain. The giant sized tumor is one that extends deeply into the brain.
There are three treatment possibilities for the acoustic neuroma. The first option is observation. These tumors grow slowly and, in some cases, it is warranted to watch the tumor and see if it is growing. This is particularly true in elderly patients with small tumors.
The second treatment option is radiation therapy. These tumors are sensitive to radiation treatment. There is a radiation treatment in which the radiation beams are focused on the tumor itself with little radiation to the surrounding tissues. This treatment is known as stereotactic radiation. Evidence suggests that this treatment keeps many smaller tumors from growing. There have been cases in which this radiation treatment has caused benign tumors to turn into malignant tumors. We know from our experience with radiation treatment in other parts of the body that it can cause or induce cancerous growth. Also, the changes and complications from radiation treatment and tissue destruction usually occur several years after the treatment. In the past, radiation treatment was used to treat benign conditions such as recurrent tonsillitis and enlarged adenoids. This treatment worked well. However, years down the line, these patients developed cancer in the surrounding area, and this treatment is no longer used. In fact, radiation treatment for this type of tumor, a benign neuroma, in any other part of the body would be considered very poor medicine. However, in the case of elderly patients that have growing tumors in which it is not likely that they will live long enough to see the side effects of radiation treatment, this is a reasonable option.
The third option is surgery. The goals in removal of acoustic neuromas surgically are tiered. The first goal is to ensure total removal of the tumor with no damage to the surrounding brain. The second goal is to preserve the facial nerve or 7th cranial nerve, which travels along with the hearing and balance nerves through the internal auditory canal. The third goal is to preserve hearing. Preservation of hearing is usually not possible with large tumors. It is possible with some smaller tumors.
There are three surgical approaches for removal of acoustic neuroma. In small tumors in which the hearing is good, the middle fossa approach is a good option. This approach involves going through the bone above the ear and gently lifting the temporal lobe of the brain and drilling the bone over the internal ear canal. This provides exposure to the tumor and it can be removed. The main advantage of this approach is preservation of hearing. The disadvantage of this approach is that it can result in some pressure on the temporal lobe of the brain and possible injury to this area and is often accompanied by some headaches postoperatively. There is a slightly greater chance of injury to the facial nerve in removing tumors with the middle fossa approach versus the next approach mentioned, the translabyrinthine approach. With small tumors, there is still only about a 50-60% chance of saving the hearing. There are some tests that can be used such as the brain stem audiometry and the electronystagmography that can help give a more accurate appraisal regarding the chances of hearing preservation.
The second surgical option is the translabyrinthine approach. This involves making an incision in the crease behind the ear and going through the ear bone directly to the tumor. The advantages of this approach include identification of the facial nerve on both sides of the tumor, as well as most of the approach to the tumor occurs outside of the area of the brain. Most of the approach is through the ear, and there is very little manipulation of the brain in removal of a tumor in this fashion. The disadvantage of the translabyrinthine approach is that it ensures total hearing loss. There is no chance to save the hearing with this approach.
The third approach is the retrosigmoid or suboccipital approach. An incision is made two inches behind the ear, and a window of bone is removed. This approach involves gently retracting the cerebellum or bottom portion of the brain out of the way to get to the tumor. In this approach, the back portion of the IAC has to be drilled out to remove the extension of the tumor into the IAC. This approach is useful in tumors that are located primarily out of the IAC that are small to medium size in which there is still good hearing. This approach does allow the possibility of hearing preservation. The disadvantage of this approach is that the facial nerve is not identified on the end of the tumor closest to the ear and it does require some pressure on the cerebellum or brain as well. This approach has also been associated with postoperative headaches.
Surgical removal of acoustic neuromas is a team effort. The neuro-otologic surgeon and the neurosurgeon work together combining their areas of expertise to work both through the ear and in and around the brain to remove these tumors and ensure optimal outcome. Although the acoustic neuroma is a benign tumor, it is in a difficult location. For this reason, the treatment of this neuroma can result in some difficulties including paralysis of the face. Other problems with removal of the acoustic neuroma besides the usual hearing loss in that affected ear include spinal fluid leak, which could necessitate another surgery, and an infection of the spinal fluid known as meningitis. Fortunately, these complications are unusual. The worst thing that can happen in removal of acoustic neuroma would be a stroke or even death. These complications are extremely rare and happen less than 1% of the time.
This surgery usually takes from 4-6 hours and involves an overnight stay in the Intensive Care Unit. The patient can expect to stay in the hospital for about five days. After the surgery, there is usually imbalance that improves over the next few days. It is recommended that the patient plan to take one month off work. There can be no lifting or straining for one month after surgery. The patient's balance should return within two weeks such that usual every day activities can be accomplished without difficulty. It usually takes about 2-3 months before the patient's balance is good enough to play tennis and perform other such activities. Many times in medium and larger size tumors, after the tumor is removed, the facial nerve works well, but there is a delayed weakness. This could require some special eye care. Long term, the facial nerve function returns within several months in most cases.
The acoustic neuroma is a condition that can be frightening at first. Fortunately, we now have very good methods through microsurgical techniques to take care of these tumors. If you have any questions, please write them down and the surgical team will answer these questions and reassure you about your recovery with this condition.
|
|
The
content of this site is intended for information purposes only; it
is not meant to take the place of seeing a healthcare
professional. If you have any concerns regarding your own or
someone else's health, we strongly encourage you to consult a
physician. |
|
