Acoustic neuroma

from Wikipedia, the free encyclopedia
Classification according to ICD-10
D33 Benign neoplasm of the brain and other parts of the central nervous system
D33.3 Cranial nerves
ICD-10 online (WHO version 2019)
Classification according to ICD-O-3
9560/0 NOS neurilemmoma
neurinoma
schwannoma NOS
acoustic neuroma (C72.4)
...
ICD-O-3 first revision online
Typical anatomical location of the acoustic neuroma
Acoustic neuroma on the right, approx. 20 x 22 x 25 mm extra- and intrameatal

An acoustic neuroma ( AKN , AN ) is a benign tumor of the Schwann cells of the vestibular portion of the VIII. Cranial nerves , the auditory and vestibular nerve ( vestibulocochlear nerve ), starts and in the inner auditory canal , with a greater extension in the cerebellum bridge angle located is. The acoustic neuroma can actually be described histologically as a vestibular schwannoma . The misnomer as acoustic neuroma is currently still clinically common. It is the most common cerebellar bridge angle tumor .

pathology

Acoustic neuromas usually occur sporadically and manifest themselves from the fourth decade of life. Neurofibromatoses with an autosomal dominant inheritance occur more frequently, especially type 1 (Recklinghausen's disease; Von Recklinghausen syndrome) and type 2 . More than 95% of all AKN are unilateral; in the presence of neurofibromatosis type 2, however, the acoustic neuroma typically occurs on both sides. Antoni A and Antoni B fibers can be found histologically, starting mostly from the upper part of the vestibular part of the 8th cranial nerve. The histological and clinical appearance is benign; malignant transformation is very rare.

Symptoms

The most common clinical symptoms are hearing loss , tinnitus , balance disorders and even dizziness . More rarely, headaches, facial numbness, double vision, nausea and vomiting, ear pain, changes in taste or facial paresis , in which the facial muscles are paralyzed due to impairment of the VIIth cranial nerve ( facial nerve ) .

A one-sided hearing impairment is usually noticed first, especially for high tones, e.g. B. when telephoning . The dizziness is mostly unsystematic, no vertigo as in a disturbance of the balance organ . Symptoms also emerge slowly. With measuring devices, on the other hand, the equilibrium component can first be detected, since the AKN does not actually start from the acoustic component ( N. cochlearis ), but rather from the balance component ( N. vestibularis ) of the N. vestibulocochlearis .

Another symptom is a decrease in touch and pressure sensitivity ( hypesthesia ) of the external auditory canal . It is known as the Hitselberger sign .

Diagnosis of acoustic neuroma

Acoustic neuroma on MRI image (arrow)

A reliable diagnosis is only provided by a histological examination after tissue removal. Clinically relevant tumors can be reliably detected with magnetic resonance imaging (MRT).

In the case of dizziness, acute infections that result in similar clinical pictures are initially excluded. A noticeable hearing loss is determined by a tone audiogram . A measurement of the early acoustic evoked potentials (FAEP) is then carried out, especially if there is a side-differential or unilateral sensorineural hearing loss. When measuring the FAEP, an acoustic neuroma shows up in the increase in the transit time of the signals from the inner ear to the brain stem . This is due to the fact that the myelin sheath of the nerve tract is damaged by the AKN and the electrical impulses can only be transported with losses. If the curve image is clearly different from one side to the other or when there are differences in transit time of the potentials, a magnetic resonance tomography of the skull should be performed with and without contrast agent in order to be able to exclude an acoustic neuroma with sufficient certainty.

Differential diagnosis

Meningiomas can grow in the region of the cerebellopontine angle and in some cases cannot be distinguished from an acoustic neuroma on MRI. Meningiomas growing completely in the internal auditory canal have also been described.

Further differential diagnoses are

therapy

There are five different options available for treating acoustic neuroma:

The choice of therapy to be initiated depends largely on tumor size and growth behavior, hearing impairment, age and general health of the patient and the connection with neurofibromatosis. A general statement about tumor growth control and the complication rate of the five forms of therapy cannot be made and depends on the individual case. Since the acoustic neuroma is not malignant and usually grows slowly over the years, surgery was often avoided, especially in older patients, and instead a regular observation of the growth in size was used. Today, the option of radiosurgery should always be considered as an alternative. In children and adolescents, on the other hand, in whom cranial nerve neuromas are extremely rare except in the context of neurofibromatosis, immediate treatment is usually initiated, as the size of the tumor can change rapidly in this group of patients and life-threatening conditions can occur within a very short time.

Microsurgery

AKN can be partially or completely removed microsurgically via various access routes. The choice of approach depends on the size of the tumor, the degree of hearing damage and the personal decision of the surgeon and patient. Classic access routes are:

  • Retrosigmoid and variants
  • Translabyrinthine
  • Subtemporal extradural

The main complications are: hearing impairment, facial paralysis and liquor fistulas. Even after a complete resection, regular MRI follow-ups are necessary.

radiotherapy

The radiation therapy is a noninvasive treatment. Radiosurgery is a special type of radiation therapy , which is usually performed on an outpatient basis in a single treatment, while radiation therapy is otherwise usually performed in a fractionated manner (i.e. in several smaller radiation doses) over several treatment days. If the tumor is already over 3 centimeters in size, radiosurgery is usually no longer indicated. In patients with neurofibromatosis , treatment with a gamma knife or linear accelerator is not or not primarily indicated, as these patients usually have acoustic neuromas on both sides. In the case of an operation that may be necessary later, irradiation of these patients can also lead to the tumor tissue being more difficult to differentiate from healthy tissue and thus the operation and its success could be negatively influenced. Both surgical treatment and radiosurgery not infrequently result in damage to the nerves of the internal auditory canal if these have not already been damaged by the tumor. Overall, however, the side effects of radiosurgery and radiation therapy are less common and less pronounced than with microsurgery. In Germany, however, patients have not yet been adequately informed about these two therapies, as a recent study has shown. The effectiveness and safety of irradiation using protons is currently being investigated in clinical studies.

chemotherapy

Due to the histological benign nature of the tumors and the associated poor response of classical chemotherapy, this has not yet been a standard option. However, Avastin (R), a monoclonal antibody against VEGF , is currently being tested in neurofibromatosis type 2 patients.

Waiting observation

If the tumor is clinically and radiologically stable, especially in older patients with smaller tumors, it may be useful to observe the tumor without surgical or radiotherapy therapy. This form of treatment is largely contraindicated for larger AKN with brainstem obstruction.

Individual evidence

  1. ↑ MD Bethesda: National Institutes of Health Consensus Development Conference: Acoustic neuroma: Consensus statement. NIH Consens Dev Conf Consens Statement. In: Public Health Service, US Department of Health and Human Services. Vol. 9, 1991.
  2. ^ SG Harner, ER Laws: Clinical findings in patients with acoustic neuromas. In: Mayo Clin Proc. 1983; 58, pp. 721-728.
  3. ↑ Peter P. Urban: Diseases of the brain stem: Clinic - Diagnostics - Therapy. Schattauer-Verlag, 2008, ISBN 978-3-7945-2478-5 , p. 255.
  4. ↑ K. Asaoka, DM Barrs, JH Sampson, JT McElveen, DL Tucci, T. Fukushima: Intracanalicular meningioma mimicking vestibular schwannoma. In: AJNR. American journal of neuroradiology. Volume 23, Number 9, October 2002, pp. 1493-1496, ISSN  0195-6108 . PMID 12372737 .
  5. ↑ R. Caylan, M. Falcioni, G. De Donato, S. Ferrara, A. Russo, A. Taibah, M. Sanna: Intracanalicular meningiomas. In: Otolaryngology - Head and Neck Surgery . Volume 122, Number 1, January 2000, pp. 147-150, ISSN  0194-5998 . PMID 10629505 . (Review).
  6. ^ DH Yock: Magnetic Resonance Imaging Of CNS Disease Mosby, St. Louis 2002, ISBN 0-323-01172-1 .
  7. ↑ M. Samii, C. Matthies: Management of 1000 vestibular schwannomas (acoustic neuromas): Surgiceal management with an emphasis on complications and how to avoid them. In: Neurosurgery 1997; 40, pp. 11-23.
  8. ↑ J. Lobato-Polo, D. Kndziolka, O. Zorro et al .: Gamma knife radiosurgery in younger patients with vestibular schwannomas. In: Neurosurgery. 2009; 65 (2), pp. 294-300; discussion pp. 300-301.
  9. ^ Mark S. Greenberg, Handbook of Neurosurgery. 7th edition. Thieme Verlag, 2010, pp. 627-631.
  10. ^ Sabine Mueller, Judith Arnolds, Ansel van Oosterhout: Decision-making of vestibular schwannoma patients. In: Acta Neurochirurgica . 2010, 152 (6), pp. 973-984, https://link.springer.com/article/10.1007%2Fs00701-009-0590-0
  11. ↑ SR Plotkin, AO Stemmer-Rachamimov, FG Barker et al: Hearing improvement after bevacizumab in patients with neurofibromatosis type 2. In: N Engl J Med. 2009; 261 (4): 358-367.

Web links

Commons : Acoustic Neuroma  - Collection of images, videos and audio files
Wiktionary: acoustic neuroma  - explanations of meanings, word origins, synonyms, translations