Phone: 518-439-4326 Fax: 518-439-6143
Disease & Treatment
Acoustic Neuroma
Vestibular Schwanomma, also known as Acoustic Neuroma, is a benign non-cancerous tumor that develops on the nerve that connects the ear to the brain. This area lies between the cerebellum and pons of the brain and is commonly referred to as the cerebello-pontine angle. The tumor develops from the insulating support cells that surround the vestibular (balance) nerve. The incidence of symptomatic acoustic neuroma has been found to be about 1 per 100,000. Several studies have shown that asymptomatic tumors may be found in as many as 2.4% of the general population by the age of 60.
Ninety percent of all cerebello-pontine angle tumors are vestibular schwanommas. The other ten percent are mostly meningiomas. Schwanommas and Meningiomas can sometimes be very difficult to differentiate radiologically. Their treatment and clinical course is, however, very similar.
Cerebellar-pontine angle tumors are treated by Neurotologists and Neurosurgeons. A Neurotologist is an Ear, Nose, and Throat doctor who has subspecialty fellowship training in the treatment of these tumors and other ear disorders.
Signs and symptoms
The tumor usually grows slowly. As it grows, it presses against the hearing and balance nerves. At first, the person may have no symptoms or mild symptoms. The most common first symptom is hearing loss in one ear. Any person that develops hearing loss on one side or a difference in the hearing between the two ears should obtain a hearing test by a qualified audiologist.
If the tumor is allowed to grow further symptoms can develop. These include dizziness and disequilibrium, numbness of the face, paralysis of one side of the face. The average growth rate of these tumors is 2mm per year but there is a very large variation. Some tumors have been shown to not grow for decades and suddenly rapidly enlarge in some individuals. This unpredictable growth rate must be cosidered when recommending treatment.
Diagnosis
Acoustic neuromas are most often diagnosed on Magnetic Resonance Imaging (MRI) scanning that is done as a workup of asymmetric hearing loss. MRI is considered the gold standard for diagnosis of these tumors. Your doctor may order a screening test called an Auditory Brainstem Response (ABR). This test has much lower sensitivity and specificity than the MRI and is quickly becoming obsolite for the diagnosis of these tumors. The ABR is still performed in some centers to predict tumor position if tumor removal surgery with hearing preservation in contemplated.
Treatment
There are three basic options for the treatment of acoustic neuromas: observation, radiation, and surgical removal.
- The first option is to simply "observe" the tumor with annual MRI scans. This approach carries the risk that the tumor may suddenly enlarge within the interval that the scans are performed since the tumor growth can be variable and non-predictable. The most important question the physician must consider is: what are the chances that the patient will have complications (hearing loss, facial nerve paralysis, death) caused by the tumor in the patient's lifetime. For elderly patients or patients in very poor general health observation of the tumor may be the safest and best course of action. For younger patients (less than 65) the risk that they will at some point in their lives have to deal with a large tumor makes the prospect of removing the tumor early when it is still small very appealing.
- Radiation therapy is another treatment option. There are various types of radiation that have been used on acoustic neuromas, including conventional radiation, fractionated radiation, and gamma knife. Radiation in general medicine is usually used for rapidly growing tumors such as carcinomas. This is because radiation works by disrupting the DNA of rapidly dividing cells thereby causing death to the cancer cell. Since acoustic tumors are slowly growing benign growths, we do not routinely advise radiation treatment. Radiation therapy is not risk-free and does not result in disappearance of the tumor. Hearing loss, facial paralysis, and serious complications have also occurred after radiation therapy. After this treatment, some patients have experienced continued tumor growth and have required surgical removal, which is much more difficult due to the effects of the radiation. If surgery is required after radiation therapy is performed the results are almost always poorer than if surgery had been done prior to radiation. This is because of the extensive scar tissue formation in the tumor area as a result of the radiation.
At the Capital Region Ear Institute tumor observation and radiation therapy are most commonly recommended in individuals over the age of 65 that have small to medium size tumors (less than 1.5cm). Larger tumors have been observed or irradiated in elderly patients and in patients in poor general health where the risk of surgery is great.
- The third option is surgery. Surgical removal of acoustic neuromas is accomplished by a team of physicians, nurses, audiologist and ancillary personnel. This team includes an internist, an anesthesiologist, a specially trained surgical nurse, a neurosurgeon and a neurotologist (ear specialist). The neurosurgeon is co-surgeon with the neurotologist. Each team member supplies his or her expertise so that the tumor may be completely excised with minimal chance of complications. Total removal of an acoustic tumor, without complications, is the goal of the management of these tumors.
Surgical Approaches
Translabyrinthine approach
This involves an incision behind the ear. The mastoid and inner ear structures are removed to expose the tumor. The great advantage of this approach is that it allows the surgeon to identify the facial nerve it its normal position where no distortion of the nerve by the tumor has occurred. The tumor is totally removed. Rarely, only partial removal is accomplished. The mastoid defect is closed with fat taken from the abdomen.
The translabyrinthine approach sacrifices the hearing and balance mechanism of the inner ear. Consequently the ear is made permanently deaf. Although the balance mechanism has been removed on the operated ear, the balance mechanism in the opposite ear usually provides stabilization for the patient in one to four months.
Middle fossa approach
An incision is made above the ear, and the brain is elevated to expose the tumor- it is totally removed in most cases . Every effort is made to preserve the hearing and still remove the tumor. In about 50% of cases, the tumor involves the hearing nerve or the artery leading to the inner ear and total loss of hearing results in the operated ear.
Suboccipital (Retrosigmoid) approach
An incision is made behind the ear and the brain is elevated to expose the tumor. The tumor is totally removed in most cases. Every effort is made to preserve the hearing and still remove the tumor. In some cases it was necessary to sacrifice the hearing to achieve tumor removal. In about 50% of cases, the tumor involves the hearing nerve or the artery leading to the inner ear and total loss of hearing results in the operated ear. Following this approach, some patients may experience persistent headaches.
What to expect if surgery is recommended:
Surgery is performed starting early in the morning.. Depending on many factors such as tumor size and location the procedure may take anywhere from a few hours to twnty hours. For extremely lage tumors it has been our practice to break the surgery into two separate procedures.
State-of-the-art facilities
Our operating rooms are dedicated to this very exacting and sub-specialized surgery. The latest technology in nerve and brain monitoring is available and routinely used. This includes:
Continuous Cranial Nerve Monitoring
Many of the major nerves that travel near the tumor can me monitored in real time. This is done with specialized sensors that are themselves monitored by a neurologist and neurophysicists. If the surgeon approaches the nerve they can be warned before serious injury results.
The Stealth™ Neuronavigation system allows the surgeion to see in real time the position of the instruments within a complicated surgical field. This is used for moderate to large tumors, or for tumors in unusual and complicated positions.
Dedicated Neurosurgical Anesthesiology
The typical hospital stay is four to five days. On the first postoperative day the patient is typically admitted to the intensive care unit. A spinal drain may or may not have been placed at the time of surgery. If a drain is placed it is usually removed by the second or third postoperative day. Patients are routinely encouraged to start walking a few days after surgery.
Recovery
Full recovery varies greatly according to the patient, type of surgical approach, and tumor size. Recovery may take several weeks to up to three months and more. Physical therapy is often recommended and greatly helps in the recovery process.
Risks and Complications of Acoustic Tumor Surgery
It is not possible to list every complication that might occur before, during or following a surgical procedure. The following discussion is included to indicate some of the risks and complications peculiar to acoustic tumor surgery.
In general, the smaller the tumor at the time of surgery, the less chance of complications. As the tumor enlarges the incidence of complication becomes increasingly greater.
Hearing Loss
In small tumors it is sometimes possible to save the hearing by removing the tumor. Most tumors are larger, however, and the hearing is lost in the involved ear as a result of the surgical procedure. Therefore, following surgery the patient hears only with the remaining good ear.
Facial Paralysis
Acoustic tumors are in intimate contact with the facial nerve which closes the eye as well as the muscles of the facial expression . Temporary paralysis of the facial nerve is common following removal of an acoustic tumor. Weakness may persist for six to twelve months. A few patients experience permanent residual weakness.
Facial paralysis may result from nerve swelling or nerve damage. Swelling of the facial nerve is common due to the fact that the nerve is usually compressed and distorted by the tumor in the internal auditory canal. Careful tumor removal, with the help of an operating microscope and facial nerve monitoring, usually results in preservation of the nerve, but nerve stretching may result in swelling of the nerve with subsequent temporary paralysis. In these instances facial function is observed for a period of months following surgery. If it becomes certain that facial nerve function will not recover (approximately 5% of cases), a second operation may be performed to connect the facial nerve to a nerve in the neck (facial hypoglossal anastomosis).
In 5% of cases the facial nerve passes through the interior of the acoustic tumor. On occasion the tumor may even originate from the facial nerve (facial nerve neuroma). In either instance it is necessary to remove all or a portion of the nerve to accomplish tumor removal. When this is necessary it may be possible to immediately reconnect the facial nerve or to remove a skin sensation nerve from the upper part of the neck to replace the missing portion of the facial nerve.
When it is not possible to reconnect or replace the facial nerve, a second operation may be performed, at a later time, to reanimate the face. One option is a facial-hypoglossal anastomosis, connecting the nerve in the neck to the facial nerve. Another option is called the facial reanimation operation. The temporalis muscle (one of the chewing muscles) is attached to the muscles of the face to help move them.
Should facial paralysis develop the eye may become dry and unprotected. Care by an eye specialist may be indicated. It may be necessary to apply artificial tears, to tape the eye shut, even to sew the eyelid closed. When prolonged facial nerve paralysis is expected an eye specialist may insert a spring eyelid closing device. This keeps the eye moistened as well as providing comfort and improved appearance.
Tinnitus
Tinnitus (ear noise) remains the same as before surgery in most cases. In 10% of the patients the tinnitus may be more noticeable.
Dizziness and Balance Disturbance
In acoustic tumor surgery it is necessary to remove part or all of the balance nerve and, in most cases to remove the inner ear balance mechanism. Because the tumor usually damages the balance system, tumor removal frequently results in improvement in any preoperative unsteadiness . Dizziness is common following surgery and may be severe for a few days. Imbalance or unsteadiness on head motion is prolonged until the normal balance mechanism in the opposite ear compensates for the loss in the operated ear, usually in one to four months. A few patients may notice unsteadiness for several years, especially when they are fatigued.
Occasionally the blood supply to the portion of the brain responsible for coordination (cerebellum) is decreased by the tumor or the removal of the tumor. Difficulty in coordination in arm and leg movements (ataxia) may result. This complication is extremely rare.
Other Nerve Weaknesses
In the rare case, acoustic tumors may contact the nerves which supply the eye muscles, the face, the mouth and throat. These areas may be injured with resultant double vision, numbness of the throat, face and tongue, weakness of the shoulder, weakness of the voice and difficulty swallowing. These problems may be permanent.
Postoperative Headache
Headache following acoustic tumor removal is common in the early postoperative period. In some rare cases, headache may be prolonged. Postoperative headache is much less when the translabyrinthine route is used than with other routs such as the sub-occipital approach
Brain Complications and Death
Acoustic tumors are located adjacent to vital brain centers which control breathing, blood pressure and heart function. As the tumor enlarges it may become attached to these brain centers and usually becomes intertwined with the blood vessels supplying these areas of the brain.
Careful tumor dissection, with the help of an operating microscope, usually avoids complications. If the blood supply to vital brain centers is disturbed, serious complications may result: loss of muscle control, paralysis, even death. In our experience death occurs rarely as the result of acoustic tumor removal.
Postoperative Spinal Fluid Leak
Acoustic tumor surgery results in a temporary leak of cerebral spinal fluid (fluid surrounding the brain). This leak is closed prior to the completion of surgery with fat removed from the abdomen. Occasionally this leak reopens and further surgery may be necessary to close it.
Postoperative Bleeding and Brain Swelling
Bleeding and brain swelling may develop after acoustic tumor surgery. If this occurs a subsequent operation may be necessary to reopen the wound to arrest bleeding and allow the brain to expand. This complication can result in paralysis or death.
Postoperative Infection
Infection occurs in less than 10% of the patients following surgery. This infection is usually in the form of meningitis, an infection of the fluid and tissue surrounding the brain.
When this complication occurs, hospitalization is prolonged. Treatment with high doses of antibiotics is often indicated. Complications from antibiotic treatment are rare.
Transfusion Reaction
It may be necessary to administer blood transfusions during acoustic tumor surgery. Immediate adverse reactions to transfusion are uncommon. A late complication of transfusion is viral infections. In most cases, a unit of the patient’s own blood can be stored before surgery for later use.