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Magnetic resonance imaging (MRI) is the most commonly used imaging scan to identify and diagnose acoustic neuromas. In this test, harmless magnetic pulses and radiofrequency waves are intermittently passed through the area of the body that is being tested. An enhancing material called gadolinium is used to detect if a tumor is present. MRI offers excellent visualization of soft tissue and the gadolinium enhances the brightness of an acoustic neuroma. Magnetic resonance imaging with the use of gadolinium is considered the "gold standard" of imaging for the diagnosis of acoustic neuromas.

A computerized tomography scan (CT scan) may be ordered in cases where an MRI cannot be performed (such as the presence of a pacemaker). Since an ordinary CT scan will not reveal small tumors still confined to the internal auditory canal, contrast materials are used to enhance the image of acoustic neuromas. In general, CT offers limited differentiation and resolution of soft tissue and is, therefore, not precise enough to delineate all acoustic neuromas.

While a CT scan and an audiogram can provide valuable information to aid diagnosis, an MRI and ABR test are generally considered to be the most accurate diagnostic tests for identifying the presence of an acoustic neuroma.

The caloric stimulation test with electronystagmography (ENG) is less commonly used for examination of nystagmus (involuntary, rapid horizontal, vertical, or rotary movement of the eyeballs) which can be an indicator of vestibular dysfunction. This test appears to lack specificity in identifying other inner ear problems and may appear as normal in people with acoustic neuromas.

Researchers from Vanderbilt University in Nashville recently described three distinct risk groups of patients presenting to the clinician with unilateral hearing loss who may fit the profile for a diagnosis of acoustic neuroma. The three risk groups are:

• Low risk group - patients in this group present with limited symptoms and the hearing loss (unilateral or bilateral) can be attributable to a specific cause. The risk of acoustic neuroma is less than 5%. An ABR test is performed to rule out acoustic neuroma.
• Intermediate risk group - patients in this group experience a sudden sensorineural hearing loss in one ear or a persistent, unexplained, unilateral tinnitus. The risk of acoustic neuroma is between 5-30% and an MRI with gadolinium should be done to rule out acoustic neuroma.
• High risk group - patients in this group experience a unilateral sensorineural hearing loss, tinnitus, and reduced speech discrimination. The risk of acoustic neuroma is greater than 30%. Patients should undergo an MRI with gadolinium and periodic follow-up with ABR.