Tuesday, January 15, 2008

How to Diagnose Acoustic Neuroma


An acoustic neuroma is a benign tumor that arises from the sheath of Schwann cells surrounding the cochlear or vestibular nerves in the internal auditory canal. It is slow-growing but eventually can occupy much of the area behind the temporal bone and begin to push on the brain, but won't invade it. Acoustic neuromas do not appear to be an inherited trait. The following steps will show how to diagnose an acoustic neuroma.


Difficulty: Challenging



Step One

Perform a Magnetic Resonance Image (MRI.) This is the definitive diagnostic test for an acoustic neuroma but is contraindicated in patients with ferromagnetic implants. Ensure the MRI uses gadolinium contrast so small tumors won't be missed. A good scan can show a tumor 1 to 2 mm in diameter.

Step Two

Run a cisternography with air-contrast if an MRI is contraindicated and the suspicion for an acoustic tumor is high. This test is highly sensitive and can detect relatively small tumors in the inner auditory canal.

Step Three

Undergo computed tomography (CT) scanning with intravenous contrast enhancement to rule out acoustic tumors larger than 1.5 cm.

Step Four

Use fast-spin echo techniques as a fast and cheaper alternative. This technology does not require gadolinium enhancement but is highly targeted and can miss other important causes of hearing loss.

Step Five

Determine the tissue type of the acoustic tumor to distinguish it from a meningioma. Antoni A tissue has elongated spindle cells tightly packed together and Antoni B tissue has a loose spongy texture.

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