Acoustic neuroma is a benign (noncancerous) brain tumor that develops along the vestibular nerve's path from the inner ear to the brainstem. It is one of the most prevalent benign brain tumor forms. Typically, the first indicator of one is hearing loss.
The cochleovestibular nerve (alternatively referred to as the eighth cranial nerve) is composed of three nerves that connect the inner ear to the brain. One branch — the cochlear nerve — is responsible for hearing. The inferior and superior vestibular nerves send balance signals to the brain via the other two branches. The nerves are encased in a layer of Schwann cells. An auditory neuroma, alternatively referred to as a vestibular schwannoma, is a tumor of these cells. If an auditory neuroma is not detected or treated promptly, it can grow large enough to push on critical brainstem structures, posing serious life-threatening complications.
Hearing loss and tinnitus are the primary symptoms of an acoustic neuroma (ringing in the ears). They occur as a result of the tumor pressing against the auditory nerve. Despite the fact that the tumor grows on the balance nerve, the imbalance is typically moderate or absent. Due to the fact that we have two balance systems, the opposing side can compensate for the tumor's slow progressive loss.
These cancers are associated with a mutation in a protein involved in tumor suppression. The tumor often develops on one side of the head and is diagnosed between the ages of 30 and 50. Acoustic neuromas are quite uncommon in children. Individuals with neurofibromatosis type 2 develop bilateral auditory neuromas due to a deficiency of the tumor suppressor protein merlin. Around 10% of all auditory neuromas occur in individuals who have neurofibromatosis.
Symptoms of Acoustic Neuroma
Acoustic neuromas often grow slowly, which results in the gradual onset of symptoms that are easy to miss or misinterpret. The following are the initial and most prevalent symptoms of an acoustic neuroma:
Hearing loss in one ear – This is often gradual, but can occur suddenly in 10% of instances.
Tinnitus is a ringing, buzzing, or loud sound in the ear that occurs in the absence of external sound.
Symptoms that are less common include the following:
Disorientation or lack of equilibriumFace numbness
Headache
Weakness of the face
Confusion in the mind
Diagnosis
Acoustic neuroma symptoms are frequently mild and sluggish to develop, making them easily neglected in their early stages. Gradual hearing loss, particularly if it happens in only one ear, should always be evaluated by a physician.
If your doctor suspects you have an acoustic neuroma, he or she will evaluate you to rule out other possible diagnoses. Typically, this evaluation will involve the following:
Examining your ears using a magnifying lens that has been illuminated
Testing your hearing using tuning forks
Performing a nose, throat, and neck examination
Examining the nerve endings in your face
Balancing your account
Additionally, your physician may offer a formal hearing test (audiogram) to ascertain the kind and extent of your hearing loss.
Your doctor may occasionally recommend an auditory brain-stem response test, also referred to as evoked potentials or evoked responses. Electrodes are implanted on the scalp to record the brain's electrical responses to various noises throughout this test. The test determines the rate at which sound travels through the brain. If a tumor is pressing on the nerve that transmits information from the ear to the brain, this test will be abnormal and will reveal a delay in transmission (the cochlear nerve).
If your examination and hearing tests indicate that you may have an acoustic neuroma, your doctor may request additional tests to confirm the diagnosis. He or she will almost always propose a magnetic resonance imaging (MRI) scan. Magnetic resonance imaging (MRI) creates images of internal body components using magnetic waves. These images can help determine whether you have an acoustic neuroma, the size of the tumor, and its location. Magnetic resonance imaging (MRI) can identify cancers as small as 2mm in diameter.
Duration Estimated
The majority of auditory neuromas grow slowly, taking years to reach a size that causes symptoms. The average annual growth rate is 2 mm. Certain auditory neuromas do grow more rapidly. At least 10% of all auditory neuromas that are discovered do not continue to grow. There is no method to determine a tumor's growth rate except through repeated MRI scans.
Prevention
Acoustic neuromas have no known cure.
Treatment
Acoustic neuromas are treated in three ways: observation, radiotherapy, and surgery.
At least 10% of auditory neuromas do not develop once they are discovered. Due to the tumor's moderate growth rate and benign nature, a follow-up MRI scan and audiogram in six to twelve months is a safe option for rapid action. If no changes are discovered, yearly examinations are sufficient to monitor the tumor. If the tumor does not demonstrate evidence of growth, no action is required. This technique carries the danger of more irreversible hearing loss occurring during the observation period.
Radiation or surgery may be necessary if the tumor exhibits signs of growth or is pressing on the brainstem. The decision between the two is complex and should be explored in detail with your surgeon and radiation oncologist. Consideration should be given to the tumor's size and location, associated health problems, age, and hearing loss.
If surgery is required, it is often performed by a neurosurgeon and an otologist. The neurosurgeon excises the tumor from the brain, while the otologist excises the tumor from the ear. Hospitalization is typically required for 4–7 days following surgery. Surgical consequences may include hearing loss and impairment to the facial nerve, which supplies motion to the face.
Radiation is a non-invasive procedure that can be used in place of surgery. It does not cure the tumor, but it frequently has the effect of halting tumor development or causing the tumor to shrink. Radiation can be administered in a variety of ways, including gamma knife surgery, stereotactic radiosurgery, proton beam radiation, and fractionated stereotactic surgery. After consultation with the radiation oncologist, a decision is taken. Radiation-related problems include hearing loss, facial nerve injury, and tumor growth.
When Should You Consult A Doctor
Consult your physician if you experience new hearing loss or tinnitus, especially if the loss of hearing or tinnitus is unilateral.
Prognosis
Acoustic neuromas are not malignant (cancerous) tumors that spread to other areas of the body. Appropriate diagnosis and treatment can help limit the losses they cause and prevent a person's lifespan from being shortened.
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