Acoustic neuroma, also known as vestibular schwannoma, can happen to anyone, and some of the causes appear sporadic. Often experts can't pinpoint what causes acoustic neuroma. Still, there are two known main acoustic neuroma risk factors:
A rare genetic disorder that disrupts normal cell growth in the nervous system, neurofibromatosis can cause tumors to grow. In these cases, acoustic neuroma tends to develop bilaterally.
If a patient has received high dose cranial radiation therapy for the treatment of cancer, they may be at risk of developing an acoustic neuroma. Procedures such as dental X-rays do not predispose a person to this disease.
Acoustic neuroma symptoms are often ear-related, causing problems with hearing and balance. These symptoms may be difficult to detect early on and can develop as the tumor grows. The canal in the skull is only large enough for the seventh and eighth cranial nerves. The eighth crania nerve travels from inside the brain stem out through a small piece of bone into the hearing apparatus, or the vestibular apparatus. As the mass grows, it can compress on both nerves, leading to the following symptoms of acoustic neuroma:
If left untreated, signs of acoustic neuroma can worsen and make swallowing, speaking, eye function (and tear production) irregular or difficult. Fluid—or even a growing tumor—can potentially build on the brain and prove life-threatening in rare, untreated cases.
An acoustic neuroma diagnosis is often difficult to make early because symptoms may be minor and appear similar to other inner ear problems. Diagnosing acoustic neuroma begins with a physician examining the patient. An acoustic neuroma hearing test, usually an audiogram, assesses the hearing in each ear. If diminished hearing is found, a patient may undergo an MRI for acoustic neuroma, CT scan or other diagnostic imaging procedure to determine if a mass is present.
Once an acoustic neuroma is diagnosed, the patient is seen by a neuro-otologist, a doctor who specializes in the ears, nose and throat (otolaryngology or ENT). Patients commonly also visit a neurosurgeon. Here at the Neurosciences Center at Brigham and Women’s Hospital, we have the Skull Base Surgery program, which is a multi-disciplinary program. This program coordinates care so the patient can see the neuro-otologist and the neurosurgeon together in the same clinic.
Acoustic neuroma treatment depends on the size and growth speed of the acoustic neuroma, severity of the patient's symptoms, and overall age and health of the patient. Doctors may choose to monitor the acoustic neuroma if the patient isn't a good candidate for surgery because of other conditions. Surgeries and radiation therapy are key treatment options.
If a patient has a relatively minor tumor with no symptoms or is of an age or has a health condition that makes surgery less appropriate, doctors may choose to monitor the benign tumor. During observation, the patient will undergo scans or MRIs to track the potential growth of the tumor and take regular hearing tests to log symptom changes.
Advanced focused radiation, known as Gamma Knife radiosurgery, shows a great success rate in acoustic neuroma. Focused radiation can be an optimal treatment choice, especially for older patients or someone not healthy enough to undergo surgery. Even though it is called radiosurgery and “knife” is in the title, the goal of focused radiation is not to remove the acoustic neuroma. The goal of targeted radiation is to hit the acoustic neuroma hard enough to stunt it into submission and stop it from growing. Some patients may also benefit from tumor shrinkage through this procedure.
Two other types of radiation therapy:
Acoustic neuroma surgery may be recommended based on the size and progression of the acoustic neuroma, the symptoms associated with the tumor and the overall health of the patient.
The advantages of the surgical removal of acoustic neuromas are twofold. The first benefit to surgery is pathologic diagnosis. By removing the tumor, neuropathologists can examine and conduct genetic tests on the tumor tissue to determine the variant of the tumor and learn more about its origin. The other advantage of surgery is that the acoustic neuroma is completely removed. Once taken out, the chances of an acoustic neuroma recurring are greatly diminished.
There are three approaches to the surgical removal of an acoustic neuroma. The best option will be determined by several factors, including the patient’s overall health.
This procedure is frequently done by our expert fellowship-trained skull base neurosurgeons in the Department of Neurosurgery and often in conjunction with experienced neuro-otologists (ENT) in a multidisciplinary team-based approach. Neurosurgeons routinely operate with neuro-otologists because they are experts in neurological disorders of the ear. Through this procedure, the team has clear access to the sides of the brain, where the seventh and eighth cranial nerve disappears into the canal. For masses outside of the canal, it is really the only approach to surgery because the middle fossa and translabyrinthine approaches don’t allow you to access the brain easily.
The procedure begins with a line incision behind the mastoid, where there is a large blood vessel called the sigmoid sinus. The procedure’s name refers to "behind" the sigmoid sinus. The neuro-otologists remove a piece of bone from the canal, which gives the neurosurgeon access to the rest of the tumor.
During surgery, the neurosurgeon attempts to peel and free the tumor from the nerves, which may have become damaged due to pressure from the mass.
The function of the seventh cranial nerve, which controls facial movement on the same side that is being operated on, is observed during surgery via a process called neuromonitoring. The nerve is stimulated electrically to monitor how the facial nerve and the cochlear apparatus are doing. Using a device that sits in the ear, the neurosurgeon can register whether a signal is being sent down the nerve and into the brain stem.
Even if the patient has no serviceable hearing at the time of surgery, the neurosurgeon will still preserve the cochlear nerve if there is a chance hearing may improve.
This surgical procedure is completed by a neuro-otologist, who approaches the surgery by entering through the hearing apparatus. With this method, there is no attempt to save hearing. Translabyrinthine is ideal if the patient has no serviceable hearing when they are diagnosed with an acoustic neuroma.
This surgical procedure doesn’t necessarily sacrifice hearing, but it is not as successful in preserving hearing as retro-sigmoid craniotomy. Middle fossa is not done very frequently.
Recovery from acoustic neuroma surgery depends on the patient’s overall health before and after surgery. Routine hospitalization usually ranges from three to five days after surgery. Immediately following surgery, acoustic neuroma surgery recovery begins with a one- to two-day stay in the Intensive Care Unit (ICU) followed by two to three days on a hospital floor with specialized neuro-trained nurses and physician assistants.
An important part of acoustic neuroma surgery is preserving the functionality of the facial nerve, which controls facial movement and the closing of the eyelid. Closing the eyelid is an important function that protects the eye—specifically the cornea. If the cornea is not protected, it can lead to a cornea ulcer and potential blindness.
After surgery, if the facial nerve is not working and the eyelid cannot close completely, a plastic surgeon may perform a temporary procedure that inserts a gold or platinum weight into the upper eyelid, giving the eyelid enough mass to fully close. Neuro-ophthalmologists—eye doctors that specialize in neurological disorders—are also a part of the multidisciplinary team approach here at the Neurosciences Center and will be part of your care after surgery to ensure the eye is cared for properly.
Depending on your age and health, the recovery period for surgical removal of the acoustic neuroma is four to eight weeks. Your dedicated skull base physician assistant will guide you through each step of the surgical process and will be available to answer any questions and concerns you may have throughout and during the follow-up process of your surgery.
It is important to note that none of the areas operated on during acoustic neuroma surgery has anything to do with personality, memory, language or movement, and you will be the same person you were prior to surgery. You will be up and walking around the day after surgery with assistance from our dedicated neuro-trained nurses during your hospitalization. Most people recover very well from cranial surgery. While you may experience pain from the incision and potentially some neck stiffness, you will get stronger each day.
An acoustic neuroma is a benign (non-cancerous) tumor near the brain, growing outside the brain on the cranial nerve. They can grow large enough to press against the brain.
Vestibular schwannoma is a common name for acoustic neuroma. The name arises because acoustic neuroma is an overgrowth of the Schwann cells that insulate the nerve of the brain and the cranial nerves. It is vestibular because it grows off the eighth cranial nerve, the vestibulocochlear nerve.
Acoustic neuroma affects about 1 in 100,000 people, most often between the ages of 30 and 60. Cases rarely develop in children.
Not all causes of acoustic neuroma are known, although a rare genetic disorder, neurofibromatosis, is one of the known causes of a small number of cases.
Acoustic neuroma can damage hearing, cause unbalance and affect facial movements. If left untreated, the benign tumor can grow and, in some cases, become life-threatening.
Acoustic neuroma treatment depends on the size and growth speed of the acoustic neuroma, severity of the patient's symptoms and overall age and health of the patient. Doctors may choose to monitor the acoustic neuroma if the patient isn't a good candidate for surgery because of other conditions. Surgeries and radiation therapy are other key treatment options.
Like all cranial surgeries, there is a risk of bleeding, infection, injury to the brain and risk of injury to one of the blood vessels in the brain that may result in a stroke, coma or even death, which is why having a well-trained and experienced care team is vital. The goal of the surgical procedure is about removing the acoustic neuroma while simultaneously preserving the facial nerve and hearing.
It takes a multidisciplinary team approach to determine the best treatment plan of each particular case of acoustic neuroma. At Brigham and Women's Hospital, our team includes specialists in neurosurgery, neuroradiology, neuro-otology, and other areas of cancer care. Our neurosurgeons are world-renowned for their expertise and advanced techniques, and they design an individualized treatment plan for each patient to provide the best possible treatment.
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Within the Department of Neurosurgery at Brigham and Women's Hospital, we have an established Skull Base Program within the Neurosciences Center that utilizes a multidisciplinary team approach for the best treatment. Our neurosurgeons commonly work with experienced neuro-otologists, neuro-oncologists, neuro-pathologists, and radiation oncologists to complete surgical procedures and determine the best method of treatment for your acoustic neuroma.
With our Neurosciences Center clinic, we have the capability to coordinate your surgeon visits with other specialists along with your specialized imaging (CT, MRI, etc.) on the same day and in the same space.
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