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.

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.

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.