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Acoustic Neuroma

Acoustic Neuroma Definition

Acoustic neuroma also known as a vestibular schwannoma is a primary intracranial tumor that is benign. This is a tumor of the cells that form myelin of the CN VIII or vestibulocochlear nerve. Neuroma is a derivation of a Greek word which means ‘tumor of the nerve'. The name ‘acoustic' is a misnomer because the tumor hardly occurs from the cochlear or acoustic part of the vestibulocochlear nerve. The precise medical name is vestibular schwannoma. This is because it engages the vestibular part of the eighth cranial nerve and it occurs from schwann cells (the cells that are responsible for the peripheral nervous system myelin sheath).

Acoustic Neuroma Diagnosis

CT that is contrast-enhanced will almost always detect the presence of acoustic neuromas (especially those that are bigger than 2.0 centimeters in diameter and projects beyond 1.5 centimeters into the cerebellopontine slant). MRI that is enhanced with gadolinium may also be able to detect smaller tumors.

Acoustic Neuroma Manifestations of the Disease

The earliest signs of acoustic neuroma include deafness of the loss of sensorineural hearing; vertigo which comes with vomiting and nausea; altered gait and a disturbance of the patient’s sense of balance; and ear pressure. Also, there are more than 80% of individuals with acoustic neuroma who have tinnitus (occurs as a steam kettle-like sound, hissing sound like that of grinding equipment or a unilateral ringing with high pitch). Big tumors which compress the nearby brainstem may also affect other local nerves of the cranium. The involvement of the local facial nerve could lead to ipsilateral weakness of the face, glandular secretion defects, and sensory defects. The vagus nerves and glossopharyngeal nerves are generally involved but their participation could lead to changes on the swallowing or gag reflex.

Acoustic Neuroma Prevalence

There are approximately 3,000 patients who are diagnosed of acoustic neuroma annually in the US. Globally, the cases are estimated at 1 in every 100,000 individuals. The incidence is at its peak on the fifth and sixth decades of an individual’s life. It has also been observed that both sexes are affected by this condition.

Acoustic Neuroma Treatment

A period of observation may be good for neuromas that are slow-growing (with MRI monitoring). Some cases require surgery where the neuromas are removed through several approaches. Microsurgery is the only approach that removes the neuroma. The parts that are removed during surgery are the inferior and superior vestibular nerves as well as the tumor. The risk that goes with surgical procedure is a defect of the facial nerve. The chances of damages to this nerve become smaller when the acoustic neuromas are also small. The bigger the tumor, the bigger are the chances of the occurrence of facial nerve defects.

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