Vestibular Schwannoma
A benign tissue growth called vestibular schwannoma (VS), also known as acoustic neuroma or neurinoma, results from an excessive proliferation of "schwann cells" in the eighth cranial nerve sheath. This nerve, also referred to as the acoustic or vestibulocochlear nerve, consists of two parts, one associated with sound transmission and the other with balance information transmission from the inner ear to the brain. The eighth cranial nerve runs adjacent to the facial nerve (seventh cranial nerve) as they both pass through a bony canal known as the internal auditory canal (IAC), where the facial nerve provides movement to the facial muscles. The origin site of acoustic neuromas is the sheath that encompasses the eighth nerve at this approximately 2 cm long canal.
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The exact cause of acoustic neuromas remains unknown. While neurofibromatosis type 2 (NF-2), an inherited condition, can cause bilateral acoustic neuromas in some children, most cases of acoustic neuromas occur spontaneously in adulthood without any indication of an inheritable pattern.
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Acoustic neuromas have a tendency to grow gradually over several years, increasing in size at their point of origin and eventually compressing normal brain tissue. While the tumor does not invade the brain, it exerts pressure on the brain as it expands. The cerebellopontine angle, a complex area at the base of the skull, is where the slowly growing tumor protrudes from the internal auditory canal.
Bilateral schwannomas are uncommon and usually associated with neurofibromatosis type 2 (NF-2). Neurofibromatosis type 1 (NF-1), also known as von Recklinghausen's disease, is a distinct genetic disorder resembling NF-2 that may occasionally present with an acoustic neuroma, although this is exceedingly rare.
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An MRI has become the standard method for evaluating patients with suspected acoustic neuromas, along with initial physical, medical history, and hearing examinations.
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The available treatment options for acoustic neuromas include observation, surgical removal, and radiotherapy (including Conventional and Gamma Knife techniques). The optimal approach for a given patient depends on factors such as the size of the tumor and the patient's age and overall health. In selecting a treatment strategy, the primary considerations are typically the preservation of serviceable hearing and the maintenance of facial nerve function.