Magnetic resonance imaging screening in acoustic neuroma

Magnetic resonance imaging (MRI) is the definitive investigation for detection of an acoustic neuroma. It is however an expensive resource, and pick-up rate of a tumor can be as low as 1% of all patients scanned. This study aims to examine referral patterns for MRI screening for patients presenting with asymmetrical sensorineural hearing loss (ASHL). A second aim was to suggest appropriate screening criteria.

All 132 MRI scans performed for ASHL in the year 2005 were reviewed retrospectively along with their case records and audiograms. In addition, MRI scans and case records were reviewed for the last 30 patients diagnosed with acoustic neuromas. Information was analyzed using 2 published protocols and additional frequency-specific defined criteria.

Two acoustic neuromas were picked up out of 132 scans performed. Of the scans performed for ASHL, a third did not fit with any of the published criteria. Of the 30 positive scans for a tumor, the patients/audiograms revealed that 10% did not fit the published criteria despite the patients having no other audiovestibular symptoms.

There appears to be no universally accepted guidelines on screening in ASHL with clinical acumen being used by most ENT consultants in this region. Applying protocols may reduce the amount of scans performed, but up to 10% of tumors may be missed by this approach.