Acoustic neuroma also referred to as vestibular schwannoma, maybe a quite rare, noncancerous and a slow-growing tumour that happens on the most nerve – vestibular leading from the internal ear to the brain. The vestibular nerves are the eighth cranial nerves, which function by transmitting sound and equilibrium (balance) information from the inner ear to the brain.
This type of tumour usually grows slowly and does not spread through the body, instead, it affects hearing, balance and facial nerves of a patient. Though acoustic neuroma may be a non-cancerous tumour, it is often dangerous if they grow large and press against the brainstem or brain. As per the medical history and records of the patients, it is estimated that only one person in every 100,000 births is diagnosed with acoustic neuroma every year and this tumour can develop at any age and sex but most ordinarily found between the age of 40 to 50.
What is Acoustic Neuroma?
Acoustic neuroma is quite a brain disorder or a brain tumour. It is also called a benign tumour since it is non-cancerous. It is a tumour that grows very slowly in the body, but it can push against vital brain structures and become life-threatening if not treated.
The nerve along which the tumour develops inside the brain is understood as the auditory nerve and it controls hearing sense. Acoustic neuromas grow as a sort of cell referred to as Schwann cell and surround nerve cells. It tends to grow slowly and sometimes it's too small and doesn't cause any signs and symptoms, but at the upper stage of acoustic neuromas, they are capable of interfering with the vestibulocochlear nerves. The size of an acoustic neuroma can vary from 2cm to 4cm or maybe more than that.
Causes of Acoustic Neuromas
The main explanation for acoustic neuromas appears to be an abnormal or non-functioning of a gene on a chromosome- NO -22. This gene produces a tumour suppressor protein that helps in controlling the growth of Schwann cells by covering the nerves. The exact cause of this tumour is still not identified by any scientists, and as per the studies and evaluations, about 8 out of 100 cases are caused by neurofibromatosis type 2 (NF2). NF2 is a rare genetic disorder and causes benign tumours in the nervous system. In most of the cases, there is no identifiable cause, but there may be some risk factors, including:
Age
Long-term exposure to loud noise
A family history of acoustic neuroma
Exposure to radiations during childhood.
Symptoms of Acoustic Neuroma
The signs and symptoms of acoustic neuroma usually vary with the sort, size of a tumour. Some of the common symptoms of an acoustic neuroma are as mentioned below -
Earache
Vomiting
Dizziness
Headaches
Vision problems
Facial numbness
Unsteadiness or loss of balance
Weakness or loss of muscle movement
Loss of sensation to at least one side of the face and mouth
Loss of the sense of taste on the rear half the tongue
Tinnitus – a perception of noise or ringing within the affected ear
Loss of hearing, usually gradual and occur on just one side or affected ear.
Diagnosis of Acoustic Neuroma
Acoustic neuroma is often difficult to diagnose in the early stages because signs and symptoms develop gradually over time. If any of the symptoms are analyzed, then certain physical tests are administered to check the presence of a tumour on the most nerve – vestibular. The most commonly used diagnostic tests are:
Physical examination of an ear
MRI and CT scans of the head
Audiometry – A test to see the functioning of the ear
BAER – Brainstem auditory evoked response
Treatment for Acoustic Neuroma
The treatment usually depends on several factors, including:
Patient’s age
The general health of the person
The size and location of the tumour.
There are several different treatments available to cure or stop the expansion of the tumour. The major treatments:
Surgery
Microsurgery
Radiation therapy
Stereotactic radiosurgery.
FAQs on Acoustic Neuroma
1. What is an acoustic neuroma?
An acoustic neuroma, also known as a vestibular schwannoma, is a non-cancerous (benign) and typically slow-growing tumour. It develops on the main nerve leading from your inner ear to your brain. This nerve, called the vestibulocochlear nerve, is responsible for both hearing and balance. Because it is benign, it does not spread to other parts of the body.
2. What are the primary symptoms of an acoustic neuroma?
The symptoms of an acoustic neuroma usually develop gradually and can be subtle at first. They stem from the tumour's pressure on the hearing and balance nerves. Common symptoms include:
- Hearing loss in one ear, which is often gradual.
- Tinnitus, which is a ringing or buzzing sound in the affected ear.
- Dizziness and loss of balance (vertigo).
- Facial numbness or weakness on one side.
- In some cases, headaches or a feeling of fullness in the ear.
3. What causes an acoustic neuroma to develop?
The exact cause of most acoustic neuromas is unknown. They arise from an overproduction of Schwann cells, which are cells that normally wrap around and insulate nerve fibres. In a small number of cases, an acoustic neuroma is linked to a genetic disorder called neurofibromatosis type 2 (NF2). However, the vast majority of cases occur in people with no family history of the condition.
4. How is an acoustic neuroma typically diagnosed?
An acoustic neuroma is primarily diagnosed through an imaging test. A doctor will first conduct a hearing test (audiometry) to check for hearing loss in one ear. If an acoustic neuroma is suspected, the most effective diagnostic tool is a Magnetic Resonance Imaging (MRI) scan with a contrast agent. The contrast material makes the tumour appear bright on the scan, allowing for a clear and definitive diagnosis of its size and location.
5. What are the common treatment options for an acoustic neuroma?
There are three main approaches to managing an acoustic neuroma, and the choice depends on the tumour's size, the patient's age and health, and the severity of symptoms. The options are:
- Observation: For small, slow-growing tumours that cause few symptoms, doctors may recommend regular monitoring with MRI scans.
- Surgery: Microsurgery can be performed to remove all or part of the tumour. The goal is to remove the tumour while preserving nerve function.
- Radiation Therapy: Stereotactic radiosurgery (like Gamma Knife) uses highly focused beams of radiation to stop the tumour from growing without making an incision.
6. Why does an acoustic neuroma affect hearing and balance?
An acoustic neuroma directly impacts hearing and balance because it grows on the vestibulocochlear nerve. This crucial nerve has two distinct parts: the cochlear nerve, which transmits sound information from the inner ear to the brain, and the vestibular nerve, which sends balance and head position signals. As the tumour enlarges, it compresses these nerve fibres, disrupting the signals and leading to symptoms like one-sided hearing loss and vertigo.
7. Is an acoustic neuroma cancerous, and what is the difference between this and a malignant brain tumour?
No, an acoustic neuroma is a benign (non-cancerous) tumour. The key difference lies in their behaviour. A benign tumour like an acoustic neuroma grows slowly and does not invade surrounding brain tissue or spread (metastasize) to distant parts of the body. In contrast, a malignant brain tumour is cancerous, grows rapidly, invades nearby tissues, and can be life-threatening.
8. If an acoustic neuroma is non-cancerous, why is it sometimes necessary to treat it?
Even though an acoustic neuroma is benign, treatment is often necessary due to its location and potential for growth. As the tumour expands within the confined space of the skull, it can press on critical structures. This pressure can cause significant problems, including:
- Severe or complete hearing loss.
- Persistent balance issues.
- Pressure on the brainstem, which can become life-threatening if left untreated.
- Impact on the facial nerve, causing facial weakness or paralysis.
9. What is the long-term outlook for someone diagnosed with an acoustic neuroma?
The long-term outlook for a person with an acoustic neuroma is generally very positive. Since the tumour is benign, it is not fatal in itself. With modern treatment options like surgery and radiosurgery, the tumour growth can be effectively controlled or eliminated in the vast majority of cases. While some side effects like partial hearing loss or balance issues may persist, the life expectancy for individuals with a treated acoustic neuroma is typically normal.
10. How does the size and location of an acoustic neuroma influence the choice of treatment?
The tumour's size and precise location are critical factors in determining the best treatment plan. For example:
- Small tumours: If a tumour is very small and not causing significant symptoms, a "watch and wait" approach with regular MRI scans is often preferred to avoid the risks of treatment.
- Medium-sized tumours: For these, the choice between microsurgery and stereotactic radiosurgery can depend on factors like the patient's age and the goal of preserving hearing.
- Large tumours: A large tumour that is already compressing the brainstem often requires surgical removal as the primary treatment, as radiation may not be sufficient or safe in these cases.
