Acoustic neuroma

Acoustic neuroma

An acoustic neuroma, also known as a vestibular schwannoma, is a non-cancerous tumour that develops in the canal connecting the brain to the inner ear. As it grows on the vestibular nerve, it can affect hearing as it presses against the auditory nerve, leading to hearing loss and tinnitus, as well as affecting balance. The good news is that treatment options are available.

What is acoustic neuroma?

An acoustic neuroma is a benign (i.e. non-cancerous), slow-growing tumour that originates from the Schwann cells of the vestibular nerve. This nerve connects the inner ear to the brainstem and is responsible for relaying information to the brain about the body’s motion and position, playing a large role in balance.

The tumour typically develops on the vestibular nerve and, as it grows larger, often presses against the auditory nerve, which plays a vital role in hearing as it transmits auditory signals from the cochlea to the brain. As the tumour gets bigger, it can impact the delicate structures of the inner ear, leading to a range of symptoms, with hearing loss being one of the most common.

Acoustic neuromas are generally very slow-growing, meaning any associated hearing loss is normally quite gradual. The impaired hearing that comes with acoustic neuroma occurs as the tumour places increasing pressure on the auditory nerve, which interferes with the transmission of auditory signals to the brain. The specific symptoms and the extent of the hearing loss can vary depending on factors such as the size and location of the tumour.

Additionally, patients may experience other symptoms like tinnitus (ringing in the ears), dizziness, imbalance and facial numbness due to the tumour's proximity to other cranial nerves and structures.

Acoustic neuroma symptoms

Whether or not a person experiences acoustic neuroma symptoms depends on the size of the tumour and how much it presses on the acoustic nerve. Among the common acoustic neuroma symptoms are gradual hearing loss, ear fullness (where it feels like water is in the ear) and persistent tinnitus (a relentless ringing in the ears), as well as issues with dizziness, vertigo and balance. In fact, more than 90% of people with acoustic neuromas experience one-sided (unilateral) hearing loss to some degree.

Some of the less common signs of acoustic neuroma are directly related to the size and location of the tumour. For example, if the tumour is pressing on the trigeminal nerve, you might experience facial numbness or tingling on the same side as the tumour, particularly on the cheek or near the corner of the mouth. You may also experience eye irritation or redness if numbness prevents regular blinking reflexes.

Facial twitching and spasms can also occur, especially in the eye, eyebrow, forehead or mouth, and facial weakness can develop if the tumour is very large. Difficulties swallowing, changes in taste, and even noticeable differences in tear production (for example, dry eyes or unexpected crying) are also less common acoustic neuroma symptoms, as are headaches and pressure caused when a large acoustic neuroma presses on the lining of the skull.

It’s important to note that all these symptoms can be caused by other health conditions, such as cholesteatoma, labyrinthitis and vestibular neuritis, and Ménière’s disease, so be sure to speak to your doctor, who can conduct or refer you for the relevant tests.

What causes acoustic neuroma?

Experts aren’t sure exactly what causes acoustic neuroma, and for most people with the condition – 95% – it occurs with no specific cause, typically affecting one ear only. There may be a genetic component for the remaining 5%: those who have the rare genetic condition neurofibromatosis type 2 (NF2). For these patients, benign tumours usually develop in the ears but can also grow within the spinal cord and brain. Those with NF2 may develop acoustic neuromas in both ears rather than just one side.

Diagnosing acoustic neuroma

The importance of catching acoustic neuromas early cannot be overstated. While they are benign and slow-growing, these tumours can still be fatal if untreated. Left to grow, they will eventually run out of space and begin to grow into the skull cavity, potentially impacting the brain stem, which is responsible for regulating vital bodily functions such as breathing, heart rate and blood pressure.

Staying up to date with regular hearing tests is an important place to start, as these can help catch any changes in your hearing. If your doctor notices anything unusual, they may send you for further testing.

Magnetic resonance imaging (MRI) is commonly used in detecting and diagnosing acoustic neuroma. While computed tomography (CT) scans may also be used if access to an MRI is not available, MRI technology is better equipped to catch smaller tumours in their early stages.

The earlier you catch a neuroma, the better, both for ease of treatment and quality of life. Nipping these growths in the bud not only helps in preserving your hearing but also prevents potential complications, like balance issues or facial weakness.

How to treat acoustic neuroma

When it comes to the question of how to treat acoustic neuroma, it often depends on how large the tumour is. For very small tumours that don’t require immediate attention, the best course of action may simply be ‘watchful waiting’ – regular monitoring of the growth and symptoms through check-ups and scans to track the slow-growing tumours’ behaviour over time. This approach is often considered for elderly patients or those with medical conditions that make surgery or radiation less favourable.

If treatment is required, both microsurgery and radiation therapy are options, and your specialist will decide which is the best approach for each patient’s individual circumstances. Microsurgery involves making a small incision behind the ear and removing the tumour. This is a more direct approach and can be especially effective for larger growths. However, there are potential side effects, including hearing loss and facial nerve damage.

For smaller tumours, a form of radiation therapy called a stereotactic procedure may be used and involves targeting the growth with focused beams of gamma radiation. The aim of this treatment isn’t to remove the tumour but rather to slow or stop its growth altogether. 

Ultimately, the treatment choice depends on several factors, like the tumour size, the patient's age, overall health and personal preferences. Your doctor will advise you on the treatment option that will achieve the best balance between effectively dealing with the tumour and preserving your quality of life.

When to seek help

Timely detection and appropriate management of acoustic neuromas are crucial to preserving hearing function and addressing other potential complications. If you’ve noticed any possible acoustic neuroma symptoms or you’re experiencing hearing loss, make an appointment to visit your local Bay Audiology clinic today.

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