ACOUSTIC NEUROMA

Acoustic Neuroma

Acoustic Neuroma

Acoustic Neuromas

An acoustic neuroma is a benign tumor that can affect the balance and hearing nerves behind the inner ear. Tumors are classified as benign or malignant based upon their growth characteristics. Benign tumors generally grow slowly and do not spread throughout the body. When they grow, they usually invade or push adjacent structures aside(Khurana 2005). Unlike benign tumors, malignant tumors like breast cancer, colon cancer, lung cancer and prostate cancer generally grow faster and can spread to other regions of the body.

Medical Definition

Few absolute contraindications to the surgical removal of an acoustic tumor exist. Serious medical illness may make surgical removal in some patients too risky(Baumgart 2007). Surgery must often be performed for large tumors with brainstem shift and obstructive hydrocephalus, even in the presence of significant medical illness. The translabyrinthine approach is contraindicated in a patient with chronic otitis media.

The decision to operate should be carefully considered when the tumor is within the internal auditory canal of a patient's only hearing ear. In some cases, observing the tumor until hearing has been lost is best, while in other cases, attempting surgical removal with hearing conservation is more prudent(Barnett 2007).

Location of Acoustic neuromas

Acoustic neuromas are intracranial, extra-axial tumors that arise from the Schwann cell sheath investing either the vestibular or cochlear nerve. As acoustic neuromas increase in size, they eventually occupy a large portion of the cerebellopontine angle. Acoustic neuromas account for approximately 80% of tumors found within the cerebellopontine angle. The remaining 20% are principally meningiomas(Auvinen 2006). In rare cases, a facial nerve neuroma, vascular tumor, lipoma, or metastatic lesion is found within the cerebellopontine angle.

                    

Description

Sound entering the ear canal causes vibrations of the tympanic membrane (eardrum). The eardrum is attached to one of three ossicles (bones) found in the middle ear and it is called the malleus. The malleus bone transmits the mechanical vibrations to another ossicle, the incus, which in turn transmits the vibrations to the smallest of the three ossicles, the stapes(Armstrong 2007). The stapes bone vibrates and sends the message to the inner ear. The inner ear is made of a bony labyrinth filled with fluid and membranes. As the stapes vibrates, the fluid in the inner ear is set into motion. The cilia on the ends of hair cells within the inner ear are bent and an electrical signal is generated and travels along the (cochlear) hearing nerve and then back to the brain. The inner ear is composed of the cochlea, which is responsible for hearing and the semicircular canals that convey balance information concerning angular acceleration of the head back to the brain(Anker 2005). Two other organs, the saccule and utricle, found in the inner ear report on the linear acceleration of the head.

The internal auditory canal contains three different types of nerves, the hearing, balance and facial nerve. The facial nerve is responsible for conducting information concerning motion of the face on that side. This is the nerve that is responsible for our ability ...