An Acoustic Neuroma also known as Vestibular Schwannoma is a slow growing tumor that develops on the cranial nerve that connects the ear to the brain. Cranial nerves are those nerves that arise directly from the brain. An acoustic Neuroma is a benign (non-cancerous) growth that forms on the sheath covering of the eighth cranial nerve called vestibulocochlear nerve. The eighth cranial nerve has two divisions, the vestibular nerve that controls the balance and the cochlear nerve that takes care of the hearing function. These two nerves are lined by Schwann cells and acoustic neuroma occurs when there is a large production of Schwann cells forming into a tumor.
Schwannoma that occurs in other peripheral nerves are largely benign unless it is a Neurofibrosarcoma - a malignant form of cancer.
Symptoms of acoustic neuroma
Diagnosis and Treatment
Diagnosing acoustic neuroma is a daunting task as the symptoms explained above are associated with many other medical conditions and it could easily be mistaken for middle ear disorder. Once suspected, doctor will advise MRI, the only test conducted to prove the presence of acoustic neuroma. Few of the hearing (audiometry) and balancing (nystagmus) tests are also conducted to assess the hearing and balance functions.
There are three options available to treat acoustic neuroma. The choice of treatment depends upon the size of the tumor, it's location and patient's age and fitness.
Micro surgery involves removing the tumor either partially or totally through surgery. Partial removal is considered when the tumor is large and the total removal leads to the damage of the facial nerve. In case of partial removal, the patient has to undergo repeated MRI scans at regular intervals to ensure that tumor is not growing again. When the tumor does not pose a risk to the adjacent nerves, one can opt for a total removal of the tumor. Though surgery is the most preferred choice of addressing the acoustic neuroma, utmost care should be taken to preserve the hearing function and the facial nerve of the patient.
Radiation is the second best option for treating acoustic neuroma. Radiation is a non-invasive treatment that uses precisely focused, narrow beams of radiation to shrink the acoustic neuroma. Currently, radiation is either delivered as single fraction stereotactic radio surgery (SRS) or as multi-session fractionated stereotactic radiotherapy (FSR). These techniques deliver high doses of radiation to the tumor and also ensure that surrounding areas and organs like brain, skull and skin receive minimum or no radiation.
SRS involves a single dose of radiation wherein multitude of radiation beams are delivered to the tumor in one single sitting. Patient need not return for treatment except for a follow up. Though SRS is very effective, it may not preserve the hearing function in most cases.
In FSR, smaller doses of radiation are given every day, over a period of three to four weeks. FSR method has better chances of preserving the hearing function compared to SRS method.
Sometimes doctors may just ask the patient to wait and watch than begin a treatment for acoustic neuroma. Holding back the treatment is most ideal when the tumor is not producing any symptoms and is small in size (less than 2 cm). Acoustic Neuroma does not require any medical intervention if the tumor is not growing rapidly. The growth of the tumor is normally observed by going for repeated MRI on a regular basis for few years. Wait and watch approach also best suits older patients with small tumors that have stopped growing. They will only be monitored periodically with the help of diagnostic tests.
When there is abnormal growth of the bone of the middle ear, otosclerosis is said to occur. This disease of ear bone degeneration is usually noticed during early adult years. The bones of the ear turn into spongy bone tissue and lead to excessive buildup of bone tissue. This impairs the hearing process since there is a barrier to sound being conducted to the inner ear. The bones are then unable to vibrate and pass the sound into the inner ear. Usually the outer and middle ear are affected, leading to conductive hearing loss. Nerves of the ears may also get affected, leading to senso-neural hearing loss. Otosclerosis is noticed to occur in persons with family history of hearing loss. Hearing may be impaired in one or both ears. This condition affects nearly 10% of the American population. Pregnancy is known to trigger this condition in some women.
One of the most common symptoms of otosclerosis is tinnitus (noise originating inside the ear). Hearing loss may be gradual, which is why this condition is not often diagnosed at the early stage. Other accompanying symptoms are dizziness and balance problems. In many cases, persons suffering from otosclerosis are not even aware of their condition and do not seek medical help. An otologist (ear physician) will need to conduct a physical examination and study the history of hearing loss This condition can be diagnosed with the help of audiometric examination and special x-rays. A CT scan of the temporal bone can help in ruling out other causes of hearing loss. The hearing and balance functions will be assessed with various tests and procedures. Audiometry, tympanometry and tuning fork tests are conducted to test the extent of hearing loss.
A hearing aid is used to treat this condition when the hearing loss is mild. You can take the help of an audiologist to choose the one that fits your specific needs best. Doses of oral sodium fluoride are known to improve otosclerosis. Sodium fluoride aids calcification of new bone and checks further otoscelerotic damage. Fluoride medication along with calcium and Vitamin D are prescribed. A surgical procedure known as stapedectomy is performed to replace the fixed stapes bone in the ear with a prosthesis. This device allows sounds waves to pass to the inner ear. The stapes bone is either completely or partially removed. The laser stapedectomy surgery is usually performed under local anaesthesia and is an outpatient procedure. Only one year is operated at a time. In most of the cases, stapedectomy benefits the patient suffering from otosclerosis. After surgery, a patient must avoid loud noises and sudden changes in pressure for a few weeks. Rarely are there complications with this surgery leading to total deafness or formation of blood clots in the ear.
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Bibliography / Reference
Collection of Pages - Last revised Date: May 28, 2022