Acoustic neuromas are benign tumors, which account for about 10% of all intracranial tumors and originate from the Schwann cells of the vestibular nerve. For this reason, the term vestibular schwannoma is more appropriate nowadays. In the healthy nervous system, these Schwann cells form an outer sheath and insulation of the nerve, thus enabling a faster transmission of signals. 95% of all vestibular schwannomas occur on one side only.
The nervus vestibularis is the cranial nerve responsible for the sense of balance and is directly located next to the auditory nerve. This explains why vestibular schwannomas can cause hearing problems, balance problems, dizziness or tinnitus, known as "ringing in the ear".
If the tumour, which often originates in the inner ear canal, spreads further, it can cause a disturbance of facial skin sensitivity or face movement because of its proximity to other cranial nerves. Very large tumors can put pressure on the neighbouring brain stem, causing a range of symptoms such as nausea, unsteadiness in walking and loss of consciousness.
Magnetic resonance tomography (MRI) enables acoustic neuroma to be accurately depicted. With high-resolution sequences, best carried out in a high-field MRI scanner (3T), also neighbouring cranial nerves and small blood vessels can be displayed, which is extremely important for planning an operation. In the case of tumors in the inner ear canal, the CT provides important information about the bone structures in addition to the MRI, which may have to be removed during a microsurgical tumour resection.
to the imaging, an ENT examination is always carried out to examine the sense
of hearing and balance. This is particularly important if tumors are observed
over a longer period of time and, if they worsen, a decision has to be made on
how to proceed.
Depending on the size and exact localisation of the individual schwannoma, a decision is first made as to whether therapy is necessary at all or whether a follow-up with regular MRI/MRI examinations is sufficient. As a rule of thumb, especially for older patients and small tumors, which hardly cause any complaints, an observation with MRI checks at regular intervals is definitely a sensible option. Observations have shown that about 80% of all vestibular schwannomas show no growth over a period of 3.5 years, especially if they are located within the inner ear canal (Stangerup SE et al: The natural history of vestibular schwannomas. Otol Neurotol, 27:547-552, 200&).
Younger patients and patients with growing tumors are more likely to require treatment for schwannomas. For smaller tumors, especially if they are not adjacent to the brain stem, there is the possibility of radiosurgical treatment, i.e. irradiating the tumour with fine gamma rays from many directions. The Hirslanden Clinic has the most modern radiation system, the CyberKnife, available for this purpose. In about 90% of cases, this can prevent further growth of small tumors.
In principle, microsurgical tumour removal is suitable for tumors of any size, but since radiosurgery may also provide good results, it is necessary to balance carefully between radiation and surgery, especially in the case of smaller tumors. In the case of larger tumors, especially those that are located near the brain stem, radiation is often not possible or only possible with an increased risk, and here the advantages of microsurgery outweigh those of radiosurgery.
Microscopic surgery is almost always performed via a retrosigmoid approach through a small skin incision behind the ear. The tumour is visualised microsurgically with the operating microscope and endoscope, then gradually reduced in size and finally resected. The cranial nerves adjacent to the tumour are electronically stimulated and measured during the operation, and their position and function are continuously monitored (see intra-operativeelectrophysiology).
of the facial nerve is a top priority and in over 95% of cases it is possible
to preserve it. Severe and permanent facial paralysis is very rare. Depending
on the size and nature of the tumour, it is often possible to preserve the
hearing nerve as well. If the tumour can be completely removed by microsurgery,
there is a very high probability of cure without tumour recurrence.
of treatment and the initial question if treatment if necessary at all, is always
individually assessed on a case-by-case basis. In our
centre, all tumors are discussed in an interdisciplinary tumour board and –
taking all factors into account – the best treatment strategy will be