Acoustic Neuroma

February 3, 2017

Acoustic neuromas, also known as “acoustics” or vestibular schwannomas is a benign, usually slow-growing tumor that develops from the balance and hearing nerves supplying the inner ear.

It is a tumor that grows from the nerves responsible for balance and hearing. More accurately called vestibular schwannoma, these tumors grow from the sheath covering the vestibulocochlear nerve. Acoustic neuromas are benign (not cancerous) and usually grow slowly. Over time the tumor can cause gradual hearing loss, ringing in the ear, and dizziness. Because of their slow growth, not all acoustic neuromas need to be treated. Treatment options include observation, surgery, and radiation.

The inner ear – The inner ear is an organ of hearing and balance. Sound waves vibrate the eardrum located in the middle ear. Three tiny bones (the incus, malleus and stapes) on the other side of the eardrum pick up the vibration and deliver it to a small organ called the cochlea, located in the inner ear. The vibration is translated into electrical impulses and passed onto the brain via the cochlear nerve.

The sense organ of balance is also located inside the inner ear. A series of fluid-filled canals, set at different angles, help the brain to pinpoint movement. As the head is moved, the fluid rolls around inside the canals and is monitored by tiny hairs. The information on the head’s position is then relayed to the brain via the vestibular nerve, which lies alongside the cochlear nerve.

An acoustic neuroma, or vestibular schwannoma, is a benign, slow-growing tumor that arises from the Schwann cells forming the sheath (covering) of the vestibulocochlear nerve. As the tumor grows, it expands from its origin inside the internal auditory canal out into the space between the brainstem and the temporal bone known as the cerebellopontine angle. The pear-shaped tumor can continue to enlarge, compressing the trigeminal nerve, which is responsible for facial sensation. Eventually, the tumor can compress the brainstem. Acoustic neuromas are classified according to their size as small (less than 1.5 cm), medium (1.5 to 2.5 cm), or large (more than 2.5 cm).

They are uncommon, and occur in approximately 10 people per million per year in the United States.They tend to be found in patients older than 40 years. The vast majority (95%) of these tumors are sporadic, meaning they are not passed on through genes. Sporatic tumors occur in only one ear, and there are no known risk factors. Rarely these tumors are associated with a genetic disease called Neurofibromatosis Type II. Patients with Neurofibromatosis develop tumors at a younger age, usually have tumors on both sides and also have other manifestations, including benign tumors of the brain and dura (the covering of the brain).


In most cases, the cause of an acoustic neuroma is unknown.

The only known risk factor for developing an acoustic neuroma is having a rare genetic condition called neurofibromatosis type 2. Acoustic neuromas grow from the Schwann cells lining the vestibulocochlear nerve, which is why they are sometimes called vestibular schwannomas. Schwann cells form a sheath around nerves, helping electrical signals to travel through the body.

It’s also not known what causes some acoustic neuromas to start growing or continue growing while others remain the same size.


A small acoustic neuroma may cause no symptoms. If you do have symptoms from an acoustic neuroma, these usually develop very gradually, as the tumour is slow-growing. The symptoms that an acoustic neuroma can cause are very common. Remember that acoustic neuromas are very rare. You should see your doctor if you have any of these symptoms, but they are more likely to be due to other conditions than a brain tumour.

The most common symptoms of an acoustic neuroma are –

Hearing loss – Some degree of deafness occurs in most people with an acoustic neuroma. Usually hearing loss is gradual and affects one ear. The type of deafness caused is called sensorineural deafness and means the nerve for hearing (the acoustic nerve) is damaged.

Tinnitus – This is the medical name for ringing in the ears. About 7 in 10 people with an acoustic neuroma have tinnitus in one ear. The sounds can vary; it does not have to be ringing like a bell. Tinnitus describes any sounds heard within the ear when there is no external sound being made. Tinnitus is a common symptom and not a disease in itself. Other causes of tinnitus include earwax, ear infections, ageing and noise-induced hearing loss.

Vertigo – This is the sensation of the room spinning, often described as dizziness. It is not a fear of heights as some people incorrectly think. This feeling of movement occurs even when you are standing still. Vertigo can be caused by other conditions affecting the inner ear. Nearly half of people with an acoustic neuroma have this symptom, but less than 1 in 10 have it as their first symptom.

Loss of feeling (facial numbness), tingling or pain – These symptoms are due to pressure from the acoustic neuroma on other nerves. The commonly affected nerve is called the trigeminal nerve which controls feeling in the face. About 1 in 4 people with acoustic neuroma have some facial numbness – this is a more common symptom than weakness of the facial muscles.

Headache – This is a relatively rare symptom of an acoustic neuroma. It can occur if the tumour is big enough to block the flow of cerebrospinal fluid in the brain. Cerebrospinal fluid is the clear, nourishing fluid that flows around the brain and spinal cord, protecting the delicate structures from physical and chemical harm. Obstruction to the flow and drainage of cerebrospinal fluid can cause a problem known as ‘water on the brain’ (hydrocephalus).

Earache – This is another rare symptom of acoustic neuroma. There are many more common causes of earache.

Visual problems – Again, these are a rare symptom. If they do happen, it is due to hydrocephalus (see above).

Tiredness and lack of energy – These are nonspecific symptoms and can be due to many causes. It is possible that a non-cancerous (benign) brain tumour could lead to this.


For small tumours, doctors may recommend no action at all, apart from regular checking. This is because an acoustic neuroma typically grows at a slow rate in the initial stages. However, often treatment is required.

Options may include –

  • Surgery – microsurgery techniques are used to remove the tumour. However, side effects can include loss of hearing and facial nerve damage. The choice of surgical approach depends on the size and location of the tumor and the degree of hearing loss. In some cases, it is possible to save hearing. With larger tumors, hearing must be sacrificed in order to successfully remove the entire tumor. Total removal of the tumor without complications is the surgical goal.
  • Stereotactic procedure – is a non-invasive treatment that directs gamma radiation at the tumour. Side effects may also be experienced with this procedure. Stereotactic radiation therapy (commonly called, radiosurgery) is a term used to describe several specific radiation techniques including Gamma Knife Surgery, LINAC, and fractionated radiosurgery, depending on the type of radiation beam and type of machinery used Stereotactic radiotherapy is a method of delivering a radiation dose in such a way as to minimize the dose of radiation to surrounding normal tissues (brain) while delivering a very high dose to the tumor.

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