Pathology / Acoustic neuroma
Acoustic neuroma
(vestibular Schwannoma)
- this is intended to be a brief overview; for more information, please check out the following sites:
- U of M site for newly diagnosed acoustic neuroma patients
- SIU site for CT and MRI images (click on 1="brain" and 2="Acoustic neuroma")
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~3000 cases/year in US (incidence rate: 1/100,000)
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highest incidence in 5th and 6th decades; sexes are equally affected
- occurs occasionally as part of von Recklinghausen neurofibromatosis - two forms:
- type I: involves the 8th nerve, just as it might any other cranial nerve - bilateral acoustic neuromas are rare in this form
- type II: autosomal dominant inheritance - characterized by bilateral acoustic neuromas that practically always occur before age 21
- almost always originate on the vestibular division of the 8th nerve, just within the internal auditory canal
- as it grows, the schwannoma will extend into the posterior fossa to occupy the cerebellopontine angle, where it can compress the 7th, 5th and (less often) the 9th and 10th cranial nerves
- at even later stages, it can displace and compress the pons and lateral medulla and obstruct CSF circulation
- earliest symptom is usually hearing loss, but not all patients seek medical advice immediately → more complicated clinical picture, which may follow this progression:
- vertigo: nausea, vomiting and pressure in the ear (similar to Ménière's disease, except periods of normalcy are rare)
- hearing loss and tinnitus (most often a unilateral high-pitched ringing, roaring or hissing)
- unsteadiness, especially when rapidly changing position, gait disturbances
- facial weakness, cheek numbness, loss of taste
- signs of increased intracranial pressure
- treatment is surgical excision (radiation therapy in some limited cases)