Acoustic neuromas are benign tumors i.e. they grow slowly without penetrating the nearest tissues. They also do not develop into secondary tumors (metastases). They are most often found in the internal acoustic meatus area (Meatus acusticus internus). Therefrom, they usually invade between the cerebellum and the pons varolii, a component of the brain stem. This area is called a pontocerebellar trigone. Therefore, the acoustic neuroma is also called a tumor of the pontocerebellar trigone.
Firstly, an ENT specialist will carefully examine the ear. The ear will be examined with an ear speculum or ear mirror to exclude other causes of the hearing loss (e.g. foreign body in the ear or inflammation). This will be followed by ear tests to assess the loss of hearing, as well as the so-called brainstem evoked response audiometry (BERA) to localize the loss of hearing.
In addition, the doctor will also examine the sense of equilibrium. The doctor makes the final diagnosis based on the skull/brain magnetic resonance imaging. This imaging review may help to accurately determine the tumor size and location, which plays an important role in further treatment. Also, this method can be used to diagnose very small neurinomas.
What treatment options exist?
Small acoustic neuromas of less than 3.5 mm diameter that do not cause symptoms should be monitored and measured every six months using MRI. Thus, tumor growth and change can be detected. No significant tumor growth has been found in 60 percent of older patients since the diagnosis is established. Spontaneous tumor regression is also possible.
The growing acoustic neuroma should be removed surgically, if possible. Surgery for smaller tumors in the acoustic meatus or inner ear area is usually performed by an ENT specialist. Larger tumors and those that are deeper in the pontocerebellar trigone shall be removed by a neurosurgeon through the hole in the calvarium. Frequently, both ENT specialists and neurosurgeons take part in the surgery.
Surgeons seek to securely remove the tumor without damaging brain tissue, nerves, and blood vessels. Alongside general surgical complications, such as haemorrhage, infection and increased risk of thrombus formation, brain interventions pose additional risk of temporary or permanent damage to the nervous system. For acoustic neuroma, especially in the case of very large tumors, impairment or even loss of hearing may occur after the surgery.
Disturbance of the sense of equilibrium (dizziness) or damage to the facial nerves is also possible.
For patients who cannot undergo surgery for other medical reasons, such as if they suffer severe heart disease and may not survive anesthesia, special radiation therapy, known as gamma knife therapy, can be used as an alternative to surgery. The radiation used here causes cell damage, after which healthy cells recover faster than tumor ones.