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About Acoustic Neuroma: What is it?
An acoustic neuroma (also called a vestibular schwannoma) is a benign, slow growing tumor that grows off the eighth cranial nerve, called the vestibulocochlear nerve. The eighth cranial nerves (one on the right and one on the left) are your hearing and balance nerves, which often explains the symptoms that people develop as these tumors get bigger. Acoustic neuromas are noncancerous tumors which means they do not spread or metastasize to any other parts of the body.
Because acoustic neuromas have the ability to grow slowly, they can stretch or press on any structures in their neighborhood including the balance nerves, hearing nerve and the nerve that moves the muscles of the face called the facial nerve. If an acoustic neuroma grows beyond an inch in size, the brainstem can be pushed on and other cranial nerves, like the trigeminal nerve (responsible for feeling the face), can begin to cause symptoms. In addition, because these tumors are located along the nerves that travel from the ear to the brain, they tend to be found in the inner ear canal, they can damage the function of the middle and inner ear.
Acoustic Neuroma Development
Acoustic neuromas arise from special cells called Schwann cells, which surround and insulate the vestibulocochlear nerve. They typically grow slowly and do not spread to other areas of the body, but they can lead to symptoms by pressing on the nerves or surrounding tissues in the area.
Most of the time, patients complain of hearing loss that affects only one ear. People often don’t even notice an issue for years due to the slow-growing nature of these tumors. Due to the hearing issues, many patients will seek out the help of a hearing specialist such as an ENT doctor first. Less commonly, people will complain of balance problems that also develop very slowly, if at all. Because they grow slowly, acoustic neuromas are typically diagnosed in patients between the age of 30 and 60 years old. Unless the tumor is quite large, acoustic neuromas are almost never life threatening.
Most patients will only have one nerve affected (the cranial nerves are paired, one on each side of the body), but some patients with a rare condition called Neurofibromatosis Type 2 may have tumors on both sides which affects both ears. The cause in most acoustic neuroma cases is unknown and is suspected to have to do with an issue with a gene on chromosome 22.
Symptoms and Diagnosis of Acoustic Neuroma
Symptoms of an acoustic neuroma are almost always related to hearing loss on the same side as the tumor. Remember, the symptoms can be mild and are often ignored until obvious to the patient. Balance issues, ringing in the ear, and other symptoms related to larger tumors can also occur. Below is a short list of possible symptoms from a growing acoustic neuroma:
- Hearing loss and/or ringing one ear
- Balance issues and difficulty walking
- Facial numbness and weakness
- Hydrocephalus (a buildup of fluid in the brain)
Depending on a patient’s symptoms, to confirm the diagnosis of an acoustic neuroma, a doctor will often examine the patient’s ear and perform a hearing test. If these examinations demonstrate loss of hearing on one side, most doctors will then order either a CT scan or a magnetic resonance scan (MRI) of the brain, with contrast, to see if there is anything visible around the hearing nerve.
Treatment of Acoustic Neuroma
The first thing to mention is that treating an acoustic neuroma is almost always something that is done electively. Meaning that patients and their loved-ones usually have time to educate themselves and obtain second opinions before deciding to have treatment. While patients “get smart” on their options, it is important to do know what is available.
In creating the best treatment plan for a patient, an experienced brain surgeon will review all of the tests and images before making any recommendation. Here are the main things an expert team will consider while making recommendations for a patient:
- Patient age, current medications, overall health and life goals/desires
- Hearing test results
- High-resolution MRI pictures (size of the tumor, compression of other structures, grow patterns vs no growth over time.
- Symptoms and symptom progression
After your brain surgeon walks through these key things with the patients, potential management options must be discussed. Potential acoustic neuroma treatment options include:
- Gamma Knife Treatment (aka Stereotactic Radiosurgery): With gamma knife, 192 small beams of radiation are safely, painlessly and accurately guided to treat the tumor. Using technology like the Leksell Gamma Knife®Icon, acoustic neuromas can be treated very effectively in an outpatient setting. No hospital stay. No incisions. No ventilator. In general, Gamma Knife is an excellent option for tumors that are less then 2.5 cm in maximal dimension and not causing significant pressure on the brainstem. It is a game changer for many patients who wish to resume normal life following an acoustic neuroma diagnosis.
- Traditional Acoustic Neuroma Surgery: Traditional surgery is an excellent treatment option when reducing the size of the acoustic neuroma is absolutely necessary. For younger patients with larger tumors, traditional surgery may be the preferred option. In cases where a small amount of tumor needs to be left behind, Gamma Knife treatment can be used to treat the remaining fragments.
- Conservative “watchful waiting” approach: It’s very important to mention that not every patient will require acoustic neuroma treatment (for example, those who have small, asymptomatic tumors). These patients will instead be monitored for tumor growth on a structured follow-up schedule. If, over time, a smaller acoustic neuroma grows, then Gamma Knife is a great option at some point “down the road”.
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