MRI in the detection of acoustic neuromas--a suggested protocol for screening.

Magnetic resonance imaging (MRI) is the definitive investigation in the detection of an acoustic neuroma and its use is becoming increasingly widespread for this purpose. In the Oxford region, this facility has been available for 3 years, resulting in the scanning of the internal auditory meati and cerebellopontine angles of 892 patients and the detection of 38 acoustic neuromas. Based on our use of this investigation over this time period, we have attempted to rationalize our entry protocol for screening by limiting the availability of the test to those patients up to 70 years of age presenting with unilateral audiovestibular symptoms in the absence of significant neurological symptoms or signs, with an average difference in hearing threshold of 15 dB between normal and symptomatic ears or unilateral tinnitus with normal hearing. By following these entry criteria, we would hope to maximize the available resources.