Home >> HealthCenter >> Condition

Please enter your email:

Acoustic Neuroma

An acoustic neuroma, also called a vestibular schwannoma, is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve (CN VIII). The term "acoustic neuroma" is a double misnomer, as the tumor never arises from the acoustic (or cochlear) division of the vestibulocochlear nerve and is not of neuron origin. The correct medical term is acoustic neurinoma (a lesser misnomer). Approximately 3,000 cases are diagnosed each year in the United States with a prevalence of about 1 in 100,000 worldwide. Incidence peaks in the fifth and sixth decades and both sexes are affected equally.

Causes

Acoustic neuromas may occur sporadically, or in some cases occur as part of von Recklinhausen neurofibromatosis, in which case the neuroma may take on one of two forms.

  • In Neurofibromatosis type I, a schwannoma may sporadically involve the 8th nerve, usually in adult life, but may involve any other cranial nerve or the spinal root. Bilateral acoustic neuromas are rare in this type.
  • In Neurofibromatosis type II, bilateral acoustic neuromas are the hallmark and typically present before the age of 21. These tumors tend to involve the entire extend of the nerve and show a strong autosomal dominant inheritance. Incidence is about 5 to 10%.

The usual tumor in the adult presents as a solitary tumor, originating in the nerve. It usually arises from the vestibular portion of the 8th nerve, just within the internal auditory canal. As the tumor grows, it usually extends into the posterior fossa to occupy the angle between the cerebellum and the pons (cerebellopontine angle). Because of its position, it may also compress the 5th, 7th, and less often, the 9th and 10th cranial nerves. Later, it may compress the pons and lateral medulla, causing obstruction of the CSF and increased intracranial pressure.

Clinical manifestations

The earliest symptoms of acoustic neuromas include ipsilateral sensorineural hearing loss/deafness, disturbed sense of balance and altered gait, vertigo with associated nausea and vomiting, and pressure in the ear, all of which can be attributed to the disruption of normal vestibulocochlear nerve function. Additionally more than 80% of patients have reported tinnitus (most often a unilateral high-pitched ringing, sometimes a machinery-like roaring or hissing sound, like a steam kettle).

Large tumors that compress the adjacent brainstem may affect other local cranial nerves. Involvement of the nearby facial nerve (CN VII) may lead to ipsilateral facial weakness, sensory impairment, and impairment of glandular secretions; involvement of the trigeminal nerve (CN V) may lead to loss of taste and loss of sensation in the involved side's face and mouth. The glossopharyngeal and vagus nerves are uncommonly involved, but their involvement may lead to altered gag or swallowing reflexes.

Even larger tumors may lead to increased intracranial pressure, with its associated symptoms such as headache, vomiting, and altered consciousness.

123
Next References

Home   |   About Us   |   Contact Us   |   Privacy   |   Terms Of Use   |   Advertise With Us   |   Sitemap
Copyright © 2019 Responsive Health
This site is intended to provide you with health information from publicly available sources, supporting vendors and partnered sources. While We make every effort to ensure that the information on this site is accurate, We make absolutely no assumption, inference, or declaration stating the information provided should be use as a source influencing any decisions on medical, diagnosis or treatment, or advice about what providers to use. The Site is an informational resource used for educational purposes only and cannot be used as a source used to make changes to medical treatment or lifestyle decisions without first consulting with your physician.