What is a vestibular schwannoma?
Vestibular schwannoma is a benign, slow-growing tumor of the nerve sheaths of the vestibular and auditory nerves (vestibulocochlear nerve). It is a neoplasm in the area of the peripheral nervous system, i.e. not a brain tumor in the narrower sense. Unlike a malignant tumor, the vestibular schwannoma neither spreads into the surrounding tissue nor does it form metastases.
Vestibular schwannomas occur only rarely. Those affected are usually in middle age, i.e. they are often around 50 years old, with women being affected twice as often as men.
Vestibular schwannoma: causes and risk factors
A vestibular schwannoma forms in the so-called Schwann cells that surround the cranial nerves and peripheral nerves. Their function is to accelerate the flow of information between the nerve fibers. When the Schwann cells proliferate and form an encapsulated tumor, experts speak of a vestibular schwannoma. The growth usually occurs on the vestibular nerve.
The causes and risk factors of vestibular schwannoma have not yet been clarified. It is neither hereditary nor transmissible. However, a hereditary disease can be the trigger if the vestibular schwannoma occurs on both sides: neurofibromatosis type 2. A genetic defect causes tumors to develop all over the body. If you are affected, both ears will go deaf. However, this genetic defect is very rare, accounting for one in 35,000 births worldwide.
In addition, an acoustic neuroma can develop in connection with the irradiation of a tumor in the head. Even years after cancer treatment has been completed, there is a possibility that former cancer patients who have undergone radiotherapy will contract the disease.
Symptoms: Hearing loss and dizziness
A vestibular schwannoma develops very slowly. It often takes years before it causes symptoms. By then it has already reached a certain size and has displaced other structures in the brain. The symptoms that occur are also non-specific and could also manifest themselves in the context of other diseases. The signs of acoustic neuroma include
- Hearing loss: One of the first signs is that those affected usually hear less well on one side. This is often noticed by chance, for example during a phone call. Usually you hear high-pitched sounds worse at first, such as birdsong. The hearing loss can progress to deafness.
- Tinnitus: Typical are one-sided ear noises such as hissing or buzzing.
- Dizziness: If the benign tumor affects your vestibular nerve, it can cause dizzy spells, balance problems and nausea. In addition, some patients’ eyes shake back and forth horizontally (nystagmus).
- Disruption of the facial nerve: If the vestibular schwannoma grows very strongly, it can press on various facial nerves (facial nerve and trigeminal nerve). As a result, your facial expressions and the feeling of your facial skin may be impaired. Facial paralysis rarely occurs.
- Symptoms of intracranial pressure: Since acoustic neuromas grow close to the brain stem, there is sometimes a risk that the tumors will constrict the brain tissue. This increases the intracranial pressure and leads to characteristic intracranial pressure symptoms such as:
- Nausea
- Vomiting
- Visual disturbances
- Headache
Vestibular schwannoma: Diagnosis with us
If you come to see us because you have poor hearing or suffer from tinnitus or dizziness, we will first ask you about the exact symptoms and the timing.
Hearing test for vestibular schwannoma
A hearing test determines how advanced the hearing loss is and whether it affects one or both ears. Brainstem audiometry is an objective test that uses an electrode behind the ear to measure whether sounds are transmitted unhindered to the brain via the auditory nerve. Balance tests and examinations for dizziness provide further indications.
Imaging procedures for vestibular schwannomas
Finally, a magnetic resonance imaging (MRI) or computer tomography(CT) scan can provide certainty. These imaging procedures conclude a possible diagnosis – or give the all-clear. The advantage of MRI is that it can also visualize very small acoustic neuromas well.
Vestibular schwannoma: prevention, early detection, prognosis
Early detection of acoustic neuroma is difficult because it usually develops slowly and causes no symptoms for years. We often notice it when you have a magnetic resonance or computer tomography scan of the head for other reasons.
The prognosis for vestibular schwannomas is usually very good. Even if the benign tumor is already larger, surgery can help. However, if parts of the tumor – the so-called tumor capsule – remain, the tumor can recur (so-called recurrence).
Treatment of acoustic neuroma: wait and see, operate later
Vestibular schwannomas are treated according to their location and size.
- Watch and wait: If the benign tumor is still small and does not cause any symptoms, it is sufficient to check it regularly. We refer to this tactic as “watch and wait”.
- Radiation: For smaller vestibular schwannomas up to 15 mm in size, it is possible to perform radiosurgery – a stereotactic one-time radiation treatment. Multiple applications over several weeks are recommended for larger vestibular schwannomas.
- Surgery: If the vestibular schwannoma has reached a critical size or is causing more severe symptoms, we can remove it surgically. If it grows close to the inner ear and the auditory canal, we perform the procedure. If it has already spread further, a neurosurgeon will operate through the skull.
The risks of vestibular schwannoma surgery
The surgical risks increase with the size of the tumor. Typical risks:
- Impairment of hearing up to and including deafness.
- Tumors over three centimetres in size also increase the risk of damaging the facial nerve.