Acoustic neuroma, medically known as a vestibular schwannoma, is a non-cancerous (benign) tumour. Despite its common name, this tumour does not originate from the acoustic nerve but from the vestibular nerve, which is responsible for maintaining balance.
The nerve for hearing and balance is the vestibulocochlear nerve, or the eighth cranial nerve, which is composed of two separate nerves: the vestibular and the cochlear nerves. Acoustic neuromas develop specifically on the vestibular nerve.
Acoustic neuromas are rare, with approximately one person in every 100,000 in India receiving this diagnosis each year. While they can develop at nearly any age, they are most often diagnosed between the ages of 40 and 50. An increase in diagnoses in recent studies may be partly attributed to improvements in MRI scanning technology.
The vestibulocochlear nerve and the facial nerve (the seventh cranial nerve) pass through a narrow passage in the skull called the internal auditory canal (IAC) to connect to the brainstem. Small acoustic neuromas are often confined to this canal. As they grow, they expand into the space between the IAC and the brainstem.
These tumours typically grow slowly, estimated at one to two millimetres per year, and do not spread to other parts of the body. Approximately one-third of patients have tumours that do not appear to grow at all, and a small percentage (1–2%) may even shrink without intervention.
The factors controlling acoustic neuroma growth are not yet fully understood. Although benign, the tumours can become dangerous if they grow large enough to press against the brainstem or the brain.
Tumour size is a crucial factor in treatment planning. Small tumours, especially those confined to the IAC, can often be monitored for growth with regular imaging exams. This approach is called active surveillance. Conversely, large tumours that are compressing the brainstem usually require surgical removal. In all cases, the treatment plan is determined through shared decision-making between the patient and the care team.
The cause of most acoustic neuroma cases is unknown. The majority occur randomly and are referred to as sporadic vestibular schwannomas. These are distinct from genetic tumours.
A rare genetic condition, Neurofibromatosis type 2, causes symptoms like hearing loss and tinnitus in both ears due to acoustic neuromas on both sides, known as bilateral acoustic neuroma. Advanced genetic testing is available for individuals concerned about this inherited syndrome.
While some theories suggest a link between exposure to loud noise or mobile phone use and an increased likelihood of acoustic neuromas, these have not been scientifically proven.
Acoustic neuroma symptoms vary from person to person and often develop slowly, leading them to be mistaken for normal age-related changes. Symptoms may include:
This is the most common symptom and can be sudden or gradual. Patients may notice difficulty understanding speech, particularly in noisy environments, or needing to switch their phone to the opposite ear.
Many patients experience a constant, high-pitched ringing sound in only the ear with the tumour. Tinnitus is a common problem affecting the general population, but when caused by acoustic neuroma, it is confined to one side.
The tumour originates from the balance nerves, so while hearing loss is common, balance symptoms can be subtle. The brain can compensate for some balance loss, meaning many patients do not notice issues with everyday activities or may attribute imbalance to aging. A common sign of unilateral balance loss is veering off to one side while walking straight, or noticing a change in balance during rapid movements like exercising or doing yoga.
Large tumours expanding into the space between the skull and brainstem can compress the brainstem and affect other nerves. Pressure on the trigeminal nerve (fifth cranial nerve) can cause facial numbness. Facial weakness, which affects the facial nerve, is typically only seen when tumours become very large.
Patients may feel a sense of fullness in the ear where the tumour is developing.
While these symptoms often indicate other health issues and not necessarily an acoustic neuroma, it is important to discuss them with a healthcare professional.
Acoustic neuromas are rare, which can make diagnosis challenging. SSCHRC has extensive experience in diagnosing this condition through a multidisciplinary team of specialists.
After a physical examination and questions about your health, a routine hearing test may reveal hearing loss or tinnitus in one ear, which are the most common warning signs. If hearing loss or tinnitus in one ear is present, an audiogram is performed to test hearing in both ears, providing crucial information about the extent of hearing loss and word understanding.
A sign of single-sided hearing loss will often prompt your doctor to order an MRI scan. The scan is typically performed with a contrast dye injection. The dye makes the tumour stand out clearly from the surrounding nerve and brain tissues, which is essential for proper diagnosis and treatment planning.
Acoustic neuromas are uncommon and complex, requiring specialised care from a highly experienced and skilled team. The physicians and professionals at SSCHRC offer comprehensive, multidisciplinary care, including audiology, physical therapy, and related services.
If you are diagnosed with an acoustic neuroma, your doctor will discuss the best treatment options based on several factors, including:
Patients naturally wish for the tumour to disappear, for their hearing and balance to be restored, and for the tinnitus to cease. However, current technology cannot fully achieve these outcomes. There are no drugs or chemotherapy treatments that will make these tumours disappear or completely reverse their impact.
While surgery can remove the tumour, it does not restore lost hearing or stop tinnitus. Similarly, stereotactic radiosurgery can halt the tumour's growth but does not prevent hearing loss or eliminate tinnitus. The primary benefit of these treatments is stopping symptoms from worsening, allowing patients to begin therapies that may reduce the tumour's overall impact.
Surgical removal of the tumour is a common treatment. Acoustic neuroma surgery is complex and delicate, requiring a team of experts across multiple specialties. Success is greatest when performed by a highly experienced surgical team, such as those at SSCHRC.
Surgical approaches include:
Your physician will recommend the most suitable surgery for your specific condition. Approaches designed to preserve hearing are available for carefully selected patients who are most likely to benefit.
Despite its name, SRS is a non-invasive treatment, not a surgical procedure, meaning it does not require an incision or general anaesthesia. It uses dozens of tiny radiation beams to precisely target tumours with a single, high dose of radiation.
For this one-day procedure, a neurosurgeon fits the patient with a headframe, and a special MRI scan is performed. A customised treatment plan is then created by the care team. The patient is positioned in the SRS machine, which uses a sophisticated and highly accurate patient positioning system. The head is placed into a cone-shaped cylinder, and an audio-visual connection allows the patient to communicate with and be seen by the treatment team. The cylinder delivers highly focused gamma rays to the tumour. The individual rays contribute a small dose, minimising damage to surrounding healthy cells, but they converge on the tumour with great intensity.
Sometimes referred to as watchful waiting, this approach is used for certain patients with small or slow-growing acoustic neuromas. Instead of immediate treatment, the patient undergoes regular monitoring to track tumour growth and progression. Treatment is only initiated if the disease progresses past a determined point. For acoustic neuroma, active surveillance involves regular MRI exams to track tumour size and audiograms to monitor hearing status.