Acoustic neuroma,or vestibular schwannoma, is a rare tumor in the brain. Usually, it will grow in size, but will not spread to other areas of the body, which means it is benign. Only thirteen people in one million are diagnosed every year with an acoustic neuroma. And it usually accounts for around eight in one hundred primary brain tumors. They are rare in children and more commonly seen in middle-aged adults, and seem to be more common in women than men.
What Is Acoustic Neuroma?
An acoustic neuroma grows from a kind of cell called Schwann cell, which covers nerve cells. This is the reason why the tumor is also known as a vestibular schwannoma. Acoustic neuromas usually grow quite slowly and they do not spread to far parts of the body. They are too small sometimes to create any symptoms or problems, but larger acoustic neuromas can interfere with the vestibulocochlear nerve.
What Causes Acoustic Neuroma?
Most of the time it is not known what causes acoustic neuromas while around 7 out of each 100 acoustic neuromas are caused by NF2, or neurofibromatosis type 2. NF2 is a very rare genetic disorder which can cause benign tumors of the nervous system. It affects around 1 in every 350,000 people. Almost all people with NF2 develop an acoustic neuroma on both acoustic nerves, and they can also cause benign tumors on the coverings of the brain and the spinal cord.
What Are the Symptoms of Acoustic Neuroma?
Often, acoustic neuroma symptoms early are subtle. A lot of people think these symptoms are the signs of aging, so it could be a while before they are diagnosed properly.
Usually, the first symptom will be a loss of hearing in one ear, followed by tinnitus or ringing in the ear, or a full feeling in the ear. Acoustic neuromas less commonly could cause hearing loss which is sudden. Additional symptoms that could happen over time include:
- A feeling that the world is spinning, or vertigo
- Balance problems
- Weakness in the face
- Tingling and numbness in the face constantly or occasionally
- Changes in taste
- Headaches
- Problems swallowing and hoarseness
- Confusion
- Unsteadiness and clumsiness
If you are experiencing any of these symptoms, see your doctor right away. Symptoms such as mental confusion and clumsiness could be a signal of a serious problem which needs treatment right away.
How Is Acoustic Neuroma Diagnosed?
Since the symptoms and signs of acoustic neuroma are likely to slowly develop and since symptoms like hearing loss are indicators of inner and middle ear problems, it can be hard for your doctor to find the tumor early on.
After talking to you about your symptoms, your doctor will ask you to take tests below:
- Audiometry or hearing test. A hearing specialist or audiologist will conduct this test, and you will hear sounds in one ear at a time. The doctor will give a range of sounds or different tones and will ask you to let them know each time you hear something. Each tone is played again at low levels to learn when you can barely hear. The audiologist could also give you different words to figure out your ability to hear.
- Scans. MRI (contrasted magnetic resonance imaging) or CT scans of your head will give you images which will confirm if there is an acoustic neuroma present.
How Is Acoustic NeuromaTreated?
There are three main types of treatment for acoustic neuromas which include monitoring, surgery and stereotactic radiosurgery.
1. Monitoring
Monitoring or watchful waiting should be the first step since acoustic neuromas are not cancerous and take time to grow, so it is not necessary to do treatment right away. Many times doctors will watch the tumor with MRI scans periodically and will suggest treatment only if the tumor grows larger or you experience serious symptoms because of it.
2. Surgery
This can involve taking out all or part of the tumor. There are four different types of surgical approaches available:
- Translabyrinthine. This involves making a cut behind the ear and taking out the bone behind the ear plus some part of the middle ear. The good thing about doing this is that it lets the surgeon see a cranial nerve that is very important before taking out the tumor. The bad thing about this is that it will cause hearing loss that is permanent.
- Retrosigmoid/sub-occipital. This involves exposing the back of the tumor by opening the skull in the back of the head. This is used to remove larger tumors and gives the possibility of keeping hearing intact.
- Middle fossa. This aims to take out a small piece of bone over the ear canal and take out small tumors which are only in the internal auditory canal, the narrow passageway between the brain and the middle and inner ear. Doing this could let patients preserve hearing.
- Total endoscopic resection. This procedure is newer and less invasive, letting surgeons takeout acoustic neuromas with a small camera put through a hole in the skull. It is offered only at major medical centers with surgeons who are specially trained.
3. Stereotactic Radiosurgery
Radiation therapy has been recommended for some cases of acoustic neuromas. This technique is state-of-the-art and makes it possible to send big doses of radiation to the tumor while lessening the exposure and damage to surrounding tissue. It is delivered in one of two ways:
- Single fraction stereotactic radiosurgery. In the procedure, several hundred small beams of radiation are aimed in a single session at the tumor.
- Multi-session fractionated stereotactic radiotherapy. In the procedure, smaller doses of radiation are given daily, which usually last over a number of weeks. This could help to preserve hearing better than the previous method.
What Is the Prognosis with an Acoustic Neuroma?
An acoustic neuroma prognosis is generally pretty good since it is a benign tumor. Usually it is very treatable and any complications are rare. However, there is generally some hearing lossafter treatment in the affected ear.