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Identifying the Tumor
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Advances in medicine have made possible the identification of small acoustic neuromas; that is, those still confined to the internal auditory canal. Routine auditory tests may reveal a loss of hearing and speech discrimination (the patient can hear sound in that ear, but cannot understand
what is being said).
An audiogram should be performed to effectively evaluate hearing in both ears. This test is important to begin the diagnosis of acoustic neuroma. Magnetic resonance imaging (MRI) is the diagnostic test that is preferred for identifying acoustic neuromas. Gadolinium, an enhancing material, is required to reveal the tumor. The image formed clearly defines an acoustic neuroma if it is present. Currently, this imaging study is the preferred test for identifying acoustic neuromas.
An auditory brainstem response test (ABR, BAER, or BSER) may be done in some cases. This test provides information on the passage of an electric impulse along the circuit from the inner ear to the brainstem pathways. An acoustic neuroma can interfere with the passage of this electrical impulse through the hearing nerve at the site of tumor growth in the internal auditory canal. This implies the possible diagnosis of an acoustic neuroma when the test is positive.
When a MRI is not available or cannot be performed, a computerized tomography scan (CT scan), with contrast, is suggested for patients in whom an acoustic neuroma is suspected. The CT scan and audiogram can provide valuable information to determine the presence of an acoustic neuroma. MRI is the "gold standard" by which diagnosis is confirmed. The technique can identify tumors only a few millimeters in diameter. Dye studies are typically done to confirm tumor and uptake with gadolinium is confirmatory.
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