Acoustic Neuroma is a non-cancerous tumour occurring in the cranial nerve of the ear. It is also known as vestibular schwannoma as it occurs in the Schwann cells of the vestibule-cochlear nerve. The vestibulocochlear nerve passes through an opening in the cranium called the internal auditory canal on its way from the brain. An acoustic neuroma almost always originate in that part of the nerve before it exits the cranium. Hence an acoustic neuroma is referred to as an intracranial tumour.
About six to seven percent of all intracranial tumours are acoustic neuromas. Being a non-malignant tumour, they don’t metastases or spread to other parts of the body. Similarly, it is also a non-invasive tumour and never invades the brain. The symptoms of the tumour occur due to the pressure it exerts in the brain as it increases in size. The pressure it exerts on the brain stem and cerebellum can cause various symptoms.
Acoustic neuromas are slow growing tumours. At times the tumour remains small and stops growing. If it remains small, no treatment is required. Treatment is necessary only when the tumour starts exerting pressure on the brain and other cranial nerves. Acoustic neuromas are typed as medial tumours and lateral tumours according to its location with respect to the structures of the brain. Similarly, a tumour less than 1.5 centimetres in size is termed as a small tumour. Those between 1.5 to 2.5 centimetres termed as medium tumour and above 2.5 centimetres as large tumours.
The major treatment options for acoustic neuroma are surgery and radiation. But a small tumour not causing any symptom is best left alone. Such tumours are usually picked up during imaging studies like X ray, CT or MRI scans done for other reasons. A watchful surveillance and periodic reviews are done to look for any increase in size. Treatment is contemplated only if the tumour starts growing beyond a certain size.
Acoustic Neuroma Surgery:
Surgery is the best treatment option that offers the chance of total cure, if complete removal is possible. Surgery is also the best option for patients with large tumours. Radiation is also best avoided in young patients because of an increased risk of long-term side effects. The main drawback of surgery is the increased risk of hearing loss and facial nerve paralysis. The major complication includes cerebrospinal fluid leak and meningitis.
Various surgical treatments are available for acoustic neuroma. The technique depends on the size of the tumour, its proximity to sensitive structures, hearing status among other factors. The aim of surgery is to remove the tumour without causing any damage to the facial nerve. Preservation of hearing is also accorded importance whenever possible.
It is not always possible to remove the tumour completely without causing damage to the brainstem or the facial nerve. In such a situation as much of the tumour as possible is removed. The surgeon will take a call regarding the exact amount of tumour to be removed during the process of the surgery. This depends on the degree of chances of injuring the facial nerve or brain stem. Inadvertent injury to the meninges can result in a leakage of cerebra spinal fluid and cause meningitis. These factors are also taken into consideration by the surgeon. Post- surgical radiation treatment is recommended if a part of the tumour is not removed.
The surgery is done under general anaesthesia. The surgical team will comprise of a neurosurgeon, head and neck surgeon, neurologist among others. The head and neck surgeon usually creates access for the neurosurgeons to micro dissect the tumour. The duration of surgery may range from four hours to eight hours. Under exceptional circumstances the surgery may take even fifteen to twenty hours.
Radiation Treatment For Acoustic Neuroma:
There are two major radiation treatments for acoustic neuroma.
Stereotactic radio surgery (SRS):
The treatment does not involve any surgery as the name suggests. The treatment involves the precise delivery of a high dose of radiation. The complications are less compared to surgery. The treatment is painless and will be over in a single day, holds lower risk of complications, takes a single day and is nearly painless. The major risks are hearing loss and facial paralysis. The treatment is not effective for large tumours that are compressing the brainstem.
Stereotactic radiotherapy (SRT)
This is another type of radiation therapy. The major advantage is that the treatment is painless and causes lesser complications as compared to surgery and SRS. The main disadvantage is the duration of treatment. The procedure may take up to thirty sittings spread over six weeks.
SRT may be a better choice than SRS for acoustic neuromas if hearing loss and facial paralysis are to be avoided. SRT delivers precise stereotactic radiation divided into multiple smaller doses called fractionation. Fractionation helps reduce the risk of radiation damage to the brainstem and cranial nerve.
The exact cause of acoustic neuroma is not known. Almost ninety percent of cases occur without any reason whatsoever. A few risk factors that may increase the chance of developing the condition have been identified. A vast majority of acoustic neuroma sufferers are in the age group of thirty to sixty. A family history of a genetic condition called neurofibromatosis type 2 may increase the chance of acoustic neuroma. In such situations the tumour occurs in both the vestibulocochlear nerve. Exposure to radiation in the head and neck region during childhood may increase the risk.
Acoustic Neuroma Symptoms:
The signs and symptoms of acoustic neuroma primarily arise due to its effect on the vestibulocochlear nerve from where it originates. Vestibulocochlear nerve is connected with hearing and maintaining the balance of the body. Hence the major symptoms of acoustic neuroma are related to problems with ear and body balance.
The signs and symptoms of acoustic neuroma may also arise due to its pressure effects on the brain. The tumour can also exert pressure on the facial nerve and the trigeminal nerve that lies close to it. The pressure effects on the facial nerve can cause a loss of function of the muscles of facial expression. Similar pressure effects on the trigeminal nerve can cause a loss of sensation in the face.
The intensity of symptoms depends mostly on the size of the tumour. Small tumours cause fewer symptoms and large tumours cause intense symptoms. Some of the most commonly identified symptoms are:
•Gradual loss of hearing, mostly limited to one ear
•Sudden loss of hearing in rare cases
•Ringing sensation or tinnitus in the affected ear
•Vertigo or dizziness
•Feeling of unsteadiness while walking or standing up
•A loss of body balance
•Numbness of one side of the face
•Weakness on one side of the face
•Large tumours may cause headache, nausea and vomiting due to pressure on the brain
•Very rarely vision problems or disorientation can occur due to the effects on the brain
Acoustic Neuroma Diagnosis:
A preliminary diagnosis of acoustic neuroma is made by evaluating the symptoms. A hearing test or audiometry is done to assess the level of hearing loss. X-rays, CT and MRI scans are done to assess the exact location and size of the tumour.
Other conditions with similar symptoms to those of acoustic neuroma include-
Acoustic neuroma treatment surgery and radiation therapy is available in all major hospitals in India. A surgical treatment for acoustic neuroma needs about six to seven days of hospitalisation. A longer hospital stay may be necessary in certain situations. The preliminary diagnostic tests may require about a couple of days. The review will be done after ten days post-surgery. Those coming for acoustic neuroma treatment in India should be ready to spend about three weeks in the country.
The cost of the surgery varies, based on the clinical condition of the patient and the hospital selected for the treatment.
Acoustic neuroma surgery is a very delicate surgery and patients who undergo this surgery require a lot of rest and recuperation after the surgery.
Post acoustic neuroma surgery, patients will experience a lot of changes and encounter certain issues related to their senses.
Following an acoustic neuroma surgery, patients will need to stay in the hospital for 3-5 days for continuous monitoring. During this time patients will be dizzy, nauseous, experience a certain amount of pain and have some discomfort in their throat.
Once the patient is discharged from the hospital, they will need to take it easy at home and not do any physical activities, unless specifically asked by their doctors. Patients will need to go back for their first check-up in two weeks from the surgery.
During their recovery period, patients may experience some of the following conditions:
•Change in hearing or loss of hearing
•Vertigo or balance issues
•Stiffness of neck
•Swelling or numbness at the site of the incision
It will take at last 1-2 months for the headaches and dizziness to disappear. For patients suffering from vertigo or balance issues, doctors will recommend certain exercises which patients need to follow diligently. If patients are facing any facial weakness or pain, then a different set of facial exercises will be recommended. For hearing loss, patients will be referred to an audiologist, who may recommend several options for hearing preservation. Some of these might be Cochlear Implants, Bone-Anchored Hearing Aid, or Auditory Brainstem Implant.
It will take at least a year before patients can be symptom free and resume all activities as before. However, each patient will have a different recovery time depending on the severity of the after-effects of the surgery.
Points to Remember:
•A patient after acoustic neuroma surgery or radiation treatment needs to take proper rest as advised.
•Wound care is of primary importance. Care should be taken to prevent any infection of the wound.
•Any symptoms like severe headache or vomiting may be indicative of meningitis and should be dealt with as an emergency.
•Strenuous exercise should be avoided.
•Precaution should be taken to prevent the formation of blood clots in the legs.
Patients should contact their doctors/hospitals immediately if they suffer from the following issues:
•Balance or walking becoming worse
•Numbness in face, arms or legs, which was not present before
•Long-term and high fever
•Facing increased difficulty in speaking or swallowing
•Extreme headaches, not relieved by pain medications
•Bleeding from or excessive swelling of the incision