Acoustic neuroma

What is acoustic neuroma?

An acoustic neuroma, also called a vestibular schwannoma, is a rare, non-cancerous tumour that grows on the nerve used for hearing and balance as it travels from your inner ear to your brain. It's usually slow-growing and doesn't spread to other parts of the body.

What are the symptoms of acoustic neuroma?

Symptoms often develop so gradually that they can go unnoticed at first. The most common signs include:

• hearing loss, usually only in one ear, affecting around 9 in 10 people with the condition
• tinnitus, a ringing or buzzing sound on the same side
• vertigo, or a sensation that you or your surroundings are spinning
• unsteadiness or problems with balance.

Larger tumours can also press on nearby nerves and cause persistent headaches, blurred or double vision, numbness, pain or weakness on one side of the face, clumsiness on one side of the body, or a croaky voice and difficulty swallowing. A small number of people lose their hearing suddenly rather than gradually.

What causes acoustic neuroma, and who is at risk?

Most acoustic neuromas happen for no obvious reason. They develop when Schwann cells, the cells that normally wrap around and protect nerve fibres, start to multiply out of control, most likely because of a fault in a gene on chromosome 22 that usually keeps their growth in check.

A small proportion of cases, around 5%, are linked to an inherited genetic condition called neurofibromatosis type 2 (NF2). NF2 typically causes tumours on the hearing nerves of both ears, tends to appear at a younger age, and is passed on to each child of an affected parent around half the time.

Acoustic neuroma is uncommon: it's estimated to affect around 1 in 100,000 people each year (NHS), and accounts for roughly 8% of tumours found inside the skull. It most often affects adults aged 30 to 60, though it can occur at other ages, particularly with NF2.

Are there different types of acoustic neuroma?

Most acoustic neuromas are unilateral, meaning they affect only one ear, and happen by chance rather than through an inherited cause. Bilateral acoustic neuromas, affecting both hearing nerves, are much rarer and are usually linked to NF2.

Tumours are also often grouped by size: small tumours are under 1.5cm, medium tumours are 1.5cm to 3cm, and large tumours are more than 3cm. Size, along with growth rate and position, strongly influences which treatment is recommended.

How is acoustic neuroma diagnosed?

Acoustic neuroma can be difficult to diagnose because its early symptoms, such as one-sided hearing loss, tinnitus and unsteadiness, are also common to other conditions, including Ménière's disease. If your GP suspects an acoustic neuroma, they'll refer you for further tests.

These usually include a hearing test to assess the pattern of any hearing loss, and an MRI scan, which is the key test for detecting a tumour and showing its exact size and position. A CT scan may also be used. Some centres carry out additional balance tests as part of a fuller assessment.

How is acoustic neuroma treated?

There are three main treatment options, and the right one for you depends on your tumour's size, position and growth rate, your hearing, your general health and your own preferences:

Monitoring

Because acoustic neuromas usually grow very slowly, around 1 to 2mm a year on average, careful monitoring with regular MRI scans is often a reasonable option rather than immediate treatment. Sources vary on how many tumours never grow at all, with estimates ranging from around a third to as many as 60-70%, and a small number even shrink without treatment.

A typical monitoring schedule involves scans at set intervals, for example at 1, 2, 3, 5, 7 and 10 years after the first scan, with treatment considered only if scans show clear growth.

Radiosurgery

Stereotactic radiosurgery, often known by the brand name Gamma Knife, delivers a precisely targeted beam of radiation to stop the tumour growing. It isn't surgery in the traditional sense: there are no incisions, and it's usually completed in a single visit without an overnight stay.

• around 90-95% of tumours stop growing after radiosurgery
• it's generally used for tumours under 3cm
• a lightweight frame is fitted to your head under local anaesthetic to keep it still during treatment
• side effects are uncommon, and most people return to their normal routine quickly afterwards.

Surgery

Surgery aims to remove all or part of the tumour and may be recommended for larger or growing tumours, or where there's a risk to the brain or surrounding structures. It's carried out under general anaesthetic by a neurosurgeon, often working with an ear, nose and throat surgeon, and can take anywhere from around 8 to 12 hours depending on the approach and tumour size.

There are three main surgical approaches, chosen based on tumour size, position and whether preserving hearing is realistic: the middle cranial fossa approach (for small tumours, with the best chance of preserving hearing), the retrosigmoid approach (suitable for tumours of any size, which may also preserve hearing), and the translabyrinthine approach (which results in permanent hearing loss on that side, and is generally used once useful hearing is already lost).

The main risks of surgery and radiosurgery are facial numbness or weakness, and further hearing loss. Roughly half of people with the smallest tumours who still have useful hearing before surgery keep that hearing afterwards, though this isn't guaranteed. Around 1 in 20 people who have surgery experience the tumour returning at some point, so regular MRI scans usually continue after treatment.

Whichever treatment path you take, ongoing support such as hearing aids, vestibular (balance) rehabilitation or facial nerve therapy may be needed afterwards to help you adjust.

When should you see a doctor?

See your GP if you have persistent or troublesome symptoms, particularly one-sided hearing loss, tinnitus or unsteadiness, that you're worried could be an acoustic neuroma. Because these symptoms overlap with more common conditions, it's easy for them to be put down to something else at first, so it's worth getting checked if they persist.

Very rarely, a large acoustic neuroma can cause a dangerous build-up of fluid in the brain (hydrocephalus). This is uncommon, as most tumours are found and treated before reaching this stage, but it's part of why persistent symptoms shouldn't be ignored.

It's also worth knowing that a 'non-cancerous' diagnosis doesn't mean the condition is trivial. Acoustic neuroma can meaningfully affect your hearing, balance and confidence, and support, whether medical, practical or emotional, is available if you need it.