Acoustic Neuroma Tumors
ACOUSTIC NEUROMA (also known as vestibular schwannoma) is a benign tumor that forms on the vestibular nerve which is the predominant nerve of the inner ear. The vestibular nerve travels from the ear to the brain and regulates balance and hearing. Usually an acoustic neuroma is slow growing, and gradually causes a loss of hearing, perhaps a ringing in the ears and balance difficulties. If you or someone you know is experiencing these symptoms, the next step is to speak with board-certified neurosurgeons of Centers for Neurosurgery, Spine & Orthopedics in New Jersey.
Symptoms
Acoustic neuromas commonly occur within the age range of 30 to 60 years of age but can occur at younger ages. Individuals may be asymptomatic if the acoustic neuroma is small and not compressing the cochlear nerve and its tributary blood supply which, if compressed, cause a loss of hearing.
Ninety percent of patients with acoustic neuroma experience gradual hearing loss in one ear not both. Rarely does an acoustic neuroma cause sudden, total loss of hearing on one side. Additional common symptoms include:
- Fluctuating hearing loss (hearing that worsens, improves, then worsens again) in one ear
- A feeling of “fullness” in one ear
- Ringing (tinnitus) in one ear
- Loss of balance or unsteadiness (ataxia)
- Nystagmus
- Dizziness (vertigo)
- Facial numbness or weakness
- Loss of facial muscle movement
Although an acoustic neuroma is typically a slow-growing tumor, the tumor can cause severe symptoms as its size increases. Large acoustic neuroma can cause facial muscle paralysis in addition to hearing loss. With further growth, these vestibular schwannomas press against the brainstem and prevent the flow of cerebrospinal fluid between the brain and spinal cord. This leads to increased pressure on brain tissue which causes headaches and confusion.
Causes & Risk Factors
An acoustic neuroma develops from the sheath of Schwann cells of the vestibular nerve. Schwann cells are a type of glial cells found in the peripheral nervous system. The formation of an acoustic neuroma is sometimes linked to mutations of a gene on chromosome 22. This chromosomal abnormality increases the production of Schwann cells on the vestibular nerve by allowing for the overproduction of a protein called merlin. The overproduction of the merlin protein may also be caused by environmental factors.
Those with the rare, genetic disorder neurofibromatosis type II are also more likely to develop an acoustic neuroma. Neurofibromatosis type II (NF2) is a disorder that causes noncancerous tumor growths throughout the nervous system. Of all genetic disorders, it is the one most associated with acoustic neuroma.
There is no known cause for the autosomal dominant genetic disorder neurofibromatosis type II. In most cases, it’s inherited. Autosomal dominant means it can be passed on to the offspring by just one parent with the gene. The chances of a child inheriting neurofibromatosis if only one parent has the NF2 gene is 50 percent.
Those with neurofibromatosis type II are more likely to develop acoustic neuromas in both ears (bilaterally) and they’re more likely to develop an acoustic neuroma earlier in life (typically by or around the age of 30-years-old).
Diagnosis
Once symptoms become apparent to family members or the patient, hopefully they will seek answers. The most common symptoms, such as hearing difficulties, tinnitus, and loss of balance are associated with other inner and middle ear conditions so often a primary care doctor, neurologist, neurosurgeon, or an ears, nose, and throat doctor initiates a work up.
After first describing symptoms to the physician, they will conduct a physical examination and if no ear wax or infection is detected, but other signs and symptoms are present, they will either order a hearing test or specialized imaging to rule in or out the presents of a brain tumor. Diagnostic testing choses are outlined below:
- Hearing test (audiometry): During the hearing test, the audiologist will measure your ability to hear sounds played at various tones. The tones are repeated at faint levels to evaluate the scope of your hearing. The audiologist may also present you with different words in an auditory format to test your hearing capabilities. This testing option would be selected if there was a low index of suspicion for a tumor.
- CAT Scan (computerized tomography): A CAT (computerized tomography) scan uses computers with rotating x-ray machine technology to take cross-sectional images of the anatomy. These images will allow your physician to evaluate the bony structures and detect any calcifications of a tumor. It will also show if tissue anatomy has been distorted but it does not show quality details of brain, muscle, or organ tissue.
- MRI Scan (magnetic resonance imaging): An MRI (magnetic resonance imaging) scan uses strong magnets and radio waves to create more detailed images of the brain, nerve, muscle, and organ tissues. MRI scans are particularly useful for analyzing the structure and specific location of brain tumors. MRI scans do not expose the patient to radiation.
- Balance testing (electronystagmography): An electronystagmography assesses your balance by checking for involuntary, rapid eye movements (nystagmus). Nystagmus can occur as the result of inner ear conditions, including the presence of an acoustic neuroma.
- BAER Exam (brainstem auditory evoked response): A BAER (brainstorm auditory evoked response) exam records the brain’s response to certain sounds to evaluate your hearing and neurological function related to your hearing. A positive BAER exam may indicate the presence of an acoustic neuroma since these tumors can disrupt the pathway that sends auditory information from your ear to your brain. However, BAER exams are often not used as the main diagnostic tool, since they can miss early cases of acoustic neuroma and/or smaller tumors.
Treatment
The treatment options for acoustic neuroma depend on the stage of the tumor and the rate at which it’s growing. If the tumor is small and not causing any symptoms, observation may be the best route. Observation is also preferred for those who are elderly and have multiple, comorbidities. Otherwise, specialized micro-surgery may be done to remove the tumor and/or radiotherapy to stop the acoustic neuroma from growing.
- Microsurgery: As its name implies, microsurgery allows surgeons to operate using very small incisions and a microscope to visualize the small structures. There are three different surgical approaches to removing the acoustic neuroma, depending on the size and location of the tumor. The translabyrinthine approach is immediately behind the ear on the affected side. The retrosigmoid approach is a bit further behind the ear than the translabyrithine approach. The middle cranial fossa approach accesses the vestibular nerve tumor just in front of the ear.
During microsurgery, the neurosurgeon may either completely remove the tumor or remove the majority of the tumor. A partial removal is done to minimize disturbing any vitals structures that the tumor may have grown into and thus reduces the risk of unnecessary postoperative neurologic deficits.
- Radiotherapy: A radio oncologist may be able to shrink or stop the growth of the tumor using radiotherapy. Due to recent technological advancements, there may be a need for only one session of radiotherapy. Otherwise, smaller doses can be administered to the acoustic neuroma across multiple sessions. Tumors treated with radiotherapy that aren’t surgically removed may begin to grow again in the future.
Regardless of the treatment plan chosen, there will be necessary MRI follow ups to evaluate how much of the tumor was removed.
CNSO’s New Jersey Team Can Help
An acoustic neuroma is just one type of brain tumor the Centers for Neurosurgery, Spine, and Orthopedics team in Northern New Jersey treats. The CNSO team includes surgeons each with over 10 years of experience successfully removing brain tumors and spine tumors along with providing an individualized and comprehensive care plan with specialists necessary to support their recovery. Contact Us today at one of our six New Jersey locations to schedule your evaluation and treatment.
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