Acoustic neuroma, commonly refered to as vestibular schwannoma, is an intracranial tumor that forms in the vestibulocochlear nerve. The vestibulocochlear nerve is the eighth of twelve cranial nerves, and is primarily responsible for conveying equilibrium (balance) and sound information from the inner ear to the brain. Acoustic neuromas can either develop randomly or, in some cases, arrise as part of a disorder known as Von Recklinhausen neurofibromatosis.
Von Recklinhausen neurofibromatosis may take on one of two forms: Neurofibromatosis type I or Neurofibromatosis type II. Neurofibromatosis type I is a benign tumor of nerve fibers that involve the vestibulocochlear nerve, other cranial nerves or the spinal root. Situations that include a tumor in the eighth nerve tipically occur in adults and are generally uncommon. Neurofibromatosis type II is a bilateral acoustic neuroma which is the most common type of von Recklinhausen neurofibromatosis. Formation normally occurs before the age of 21 and tends to effect the majority of nerves that sourrond the eighth nerve. The tumor can grow to croud the fifth, seventh and on rare occuasions the ninth and tenth cranial nerves. Later, it is possible the tumor can cram the pons and lateral medulla which can block the crerbrospinal fluid and increase intracranial pressure.
It is possible, however rare, for acoustic neuromas to develop in other cranial nerves or in spinal nerve roots. These infrequent situations result in weak or numb nerves and/or spinal cord compression. Trigeminal neuromas (which are extremely uncommon)
Acoustic Neuroma Signs & Symptoms
A damaged vestibulocochlear nerve, resulting from an acoustic neuroma, can affect a patient with total or partial hearing loss, a lack of balance, ear pressure, and/or nausea. Eight of ten patients experience tinnitus, which causes the perception of sound in the absence of a corresponding external stimulus. Larger acoustic neuromas crowd the brainstem, causing the impairment of taste and other senses of the mouth and/or face.
Acoustic Neuroma Diagnosis
Computed tomography (CT scan) will reveal the majority of acoustic neuromas that are larger then 2.0 cm in diameter and have invaded 1.5 cm or more into the cerebellopontine angle. Magnetic resonance imaging, or MRI, is used to detect smaller neuromas. Audiology and vestibular examinations are studied using air and bone conduction threshold observations.
Acoustic Neuroma Treatment
The most common resolutions are surgical resection and radiotherapy (also known as radiation therapy). Patients that are not candidates for surgical resection often undergo more conservative treatments that cause the tumors to grow more slowly, but are not necessarily intended to be curative. MRI’s are conducted annually to monitor tumor growth and/or treatment success. Acoustic neuromas are known to shrink at random, without treatment.
Acoustic Neuroma Prognosis
Equilibrium imbalances, loss of hearing and other sensorial abnormalities are the most common long-term effects of acoustic neuromas. If the tumor is not detected early and treated promptly, the disease can lead to permanent sensorial damage or to death. Surgical resection and radiation treatments, though, can be curative and allow the patient to live a symptom-free life.