Vestibular schwannoma

An acoustic neuroma ( AKN) is a benign tumor, which, emanating from the Schwann cells of the vestibular portion of the eighth cranial nerve, the hearing and balance nerve ( vestibulocochlear nerve ) and in the internal auditory canal, is located at a larger expansion in the cerebellopontine angle. The acoustic neuroma is also called a vestibular schwannoma, is the most common cerebellopontine angle tumor.

• 4.1 microsurgery
• 4.2 Ionic Therapy
• 4.3 chemotherapy
• 4.4 Zuwartendes Watch

Pathology

Acoustic neuromas usually occur sporadically and are manifested from the fourth decade of life. High incidence is in the autosomal dominant neurofibromatosis, especially type 1 (Morbus Recklinghausen, Recklinghausen disease) and type 2 More than 95 % of all AKN are one-sided, in the presence of neurofibromatosis type 2, the acoustic neuroma occurs, however, typically on both sides. Histologically, Antoni A and Antoni B fibers, starting mostly from the upper portion of the vestibular portion of the eighth cranial nerve. The histologic and clinical appearance is benign, malignant transformation is very rare.

Symptoms

Most common clinical symptoms are hearing loss, tinnitus, balance problems to dizziness. More rarely it can cause headaches, facial numbness, double vision, nausea and vomiting, ear pain, taste changes or facial palsy, in which there is impairment by the VII cranial nerve (facial nerve ) to a paralysis of the facial muscles.

Usually, one -sided hearing loss, especially for high notes fall on first, eg when calling. The vertigo is usually unsystematic, no vertigo like a fault of the vestibular system. Also, the symptoms progress slowly. By contrast, first measuring the equilibrium component is traceable as the AKN actually not from the acoustic content ( cochlear nerve ), but from the equilibrium proportion ( vestibular nerve ) of the vestibulocochlear nerve originates.

Another symptom is a reduction of touch and pressure sensitivity ( hypoaesthesia ) of the external auditory canal. It is called Hitselberger characters.

Diagnosis of acoustic neuromas

A reliable diagnosis provides only the histological examination of tumor tissue under the microscope. Magnetic resonance imaging ( MRI) comes this security today and is very close to diagnosis for affected people usually sufficient. However, since the symptoms of the AKN are also many other diseases common and this method of investigation is still expensive, the following approach is taken:

For dizziness first acute infections are excluded, which result in similar clinical pictures. A striking hearing loss is detected by a pure tone audiogram. After a measurement of the early auditory evoked potentials ( ABR ) is carried out, especially when a lateral differences or unilateral sensorineural hearing loss is present. When measuring the ABR is an acoustic neuroma in the runtime increase of the signals from the inner ear to the brain stem shows. This is because that by AKN the myelin sheath of nerve path is broken and the electrical pulses can be transported only by losses. With significantly seitendifferentem graph or page differents delay differences of the potentials of a magnetic resonance imaging of the head with and without contrast medium should be performed to rule out with sufficient certainty an acoustic neuroma can.

Differential Diagnosis

Meningiomas can grow in the region of the cerebellopontine angle and can not be distinguished on MRI in some cases of acoustic neuroma. Also complete growing in the internal auditory canal meningiomas have been described.

Other differential diagnoses are

• Schwannoma of the facial nerve or other cranial nerves in the region
• Metastases
• Lymphomas
• Sarcoidosis
• Tuberculosis
• Herpes zoster oticus

Therapy

For the treatment of acoustic neuromas are five different options are available:

• Microsurgery,
• Radiosurgery, eg using Gamma Knife or CyberKnife
• Radiotherapy with a linear accelerator
• Chemotherapy
• Zuwartendes monitoring ( so-called watchful waiting )

The choice of the actions to therapy largely depends on tumor size and growth behavior, hearing impairment, age, and general health of the patient and associated with neurofibromatosis. A general statement about tumor growth control and complication of the five forms of treatment can not be made to depend on the individual case. As the acoustic neuroma is not cancerous and usually grows slowly over many years, was often apart from surgery, and instead gone to a regular monitoring of the size growth, especially in elderly patients. Today is always here also the alternative possibility of radiosurgery to consider. In children and adolescents, however, where except in the context of neurofibromatosis Hirnnervenneurinome are extremely rare, immediate treatment is usually initiated, as in this patient group can change the size of the tumor rapidly and thus may life-threatening conditions occur within a short time.

Microsurgery

Micro Surgical AKN can be removed through various channels partially or completely. The choice of access route depends on tumor size, degree of hearing loss as well as personal choice of surgeon and patient. Classical access routes are:

• Retrosigmoidal and variants
• Translabyrinthär
• Subtemporal extradural

Major complications include hearing deterioration, facial paralysis and CSF leaks. Even after complete resection regular MRI follow-ups are necessary.

Ionic therapy

Both radiosurgery and radiation therapy are non-invasive treatments. Radiosurgery is usually carried out on an outpatient basis in a single treatment, while the radiation fractionated usually (i.e. in a plurality of smaller doses of radiation ) is applied to a plurality of days of treatment carried out. If the tumor is already a size of about 3 centimeters, radiosurgery is usually not indicated. In patients with neurofibromatosis treatment by gamma knife or linear accelerator is not, or not primarily indicated, as these patients usually have bilateral acoustic neuromas. Also, an irradiation in these patients result in an operation that might become necessary mean that the tumor tissue from healthy tissue is less definable and thus the operation and its success could be adversely affected. Both the surgical treatment and radiosurgery have not infrequently damage to the nerves of the internal auditory canal injury if they were not already damaged by the tumor. Overall, the side effects of radiotherapy and radiosurgery, however, are rare and less than microsurgery. In Germany so far, however, patients are still poorly informed on these two therapies elucidated, a recent study has shown. The effectiveness and safety of irradiation with protons is currently being investigated in clinical trials.

Chemotherapy

Due to the histological benign nature of the tumors and the associated poor response of classical chemotherapy, this is so far no default option. However, at present is Avastin ( R), tested a monoclonal antibody against VEGF, in neurofibromatosis type 2 patients.

Zuwartendes Watch

In clinical and radiological stability of the tumor, especially in older patients with smaller tumors, it may be useful to observe the tumor without surgical or radiotherapeutic therapy. For larger AKN Hirnstammbedrängung with this form of treatment is largely contraindicated.