Acoustic neuroma (vestibular schwannoma)
Acoustic neuroma (also known as a vestibular schwannoma) is a low grade brain tumour accounting for 8% of all primary brain tumours. They tend to affect adults between the ages of 30 to 60. Vestibular schwannomas are slow growing and are rarely life threatening.
This type of tumour grows along the eighth cranial nerve in the brain, also known as the acoustic or vestibulocochlear nerve. As the nerve controls hearing and balance, loss of hearing in one ear, or problems with balance, are common symptoms. The tumour arises from a type of cell called a schwann cell. Schwann cells wrap themselves around nerves to protect them and support their function.
What are the symptoms of acoustic neuroma?
An acoustic neuroma can sometimes be difficult to diagnose and their symptoms can be similar to other conditions such as Ménière's disease, a condition that affects the inner ear causing progressive deafness and attacks of tinnitus and vertigo.
Key symptoms include:
- Hearing loss - the first symptom in 90% of patients is a reduction in hearing in one ear, often accompanied by ringing in the ear called tinnitus. This usually progresses with time, although some patients may experience a sudden loss of hearing. Some people also experience a feeling of 'fullness' in the affected ear. Diagnosis can often be delayed as this can be misdiagnosed as age-related hearing loss or exposure to high levels of noise earlier in life
- Vertigo (sensation of your surroundings spinning) - unsteadiness and balance problems may occur during the growth of the tumour. This is due to the location of where the tumour arises on the eighth cranial nerve
Larger tumours may lead to increased pressure in the brain, in turn causing headaches and blurred or double vision. If the tumour presses on the facial nerve (trigeminal nerve), it can cause facial numbness and tingling. Even with treatment, symptoms such as tinnitus and hearing loss can persist. These symptoms will require additional treatment.
What causes Acoustic Neuromas?
The cause of acoustic neuroma is unknown, however around 7% of cases are caused by a rare genetic disorder known as Neurofibromatosis type 2 (NF-2). This type of genetic condition causes low grade tumours to grow along your nerves. NF-2 is caused by a permanent change, or gene mutation, in the DNA sequence that makes up a gene. This in turn means that the growth of nerve tissue can become uncontrolled. In half of all cases of NF-2, the mutation is passed on from one generation the other. i.e. parent to child. Although there are genetic tests that can be carried out during pregnancy to test whether your child will have NF-2, it is normally diagnosed after birth.
How is an acoustic neuroma diagnosed?
If you have a suspected acoustic neuroma, your doctors need to find out as much as possible about the position and size of your tumour so they can plan your treatment. Routine auditory tests may reveal a loss of hearing and speech decline. An audiogram will be performed to evaluate the level of hearing in both ears and sometimes a test is done to check your sense of balance. The doctor will also test your reflexes and the strength in your arms and legs. If there is a noticeable loss of hearing in one ear, a Magnetic Resonance Imaging (MRI) scan will be performed.
Magnetic resonance imaging (MRI) is the preferred diagnostic test to identify these tumour times. If you are having an MRI scan, you will be asked if you have a pacemaker, any implants, such as a programmable shunt or skull section, or if you are likely to have any metal in your body due to working in the steel or metal industries. If you have, then an MRI may not be suitable for you as it uses magnetic fields to take images. Your radiographer will be able to tell you more.
When an MRI cannot be performed, a computerized tomography (CT) scan with contrast is suggested.
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