Objective auditory brainstem response threshold deficits in patients with cerebellopontine angle tumors

The established criteria of auditory brainstem responses (ABR) such as peak latency and interaural differences of latency or amplitude have been found to be sensitive for detecting tumors of the cerebellopontine angle if a re sponse is present. However, the ABR can be absent in cases of acoustic neur omas because of desynchronization, even though pure-one audiometry indicate s that responses should be present. This retrospective study compared the A BR and pure-tone thresholds in 234 cases with cerebellopontine angle tumors and a control group of 181 cases with sensory hearing losses in order to q uantify threshold discrepancies. The average deficit of the objective ABR t hreshold (DOABRT) to the subjective pure-tone threshold for those frequenci es between 1-6 kHz was 3.6 dB for the control group (ABR and pure tone thre sholds very close) and 31.2 dB for the tumor group (ABR threshold much high er than the pure-tone threshold). ABR thresholds 30 dB higher than the high -frequency pure tone thresholds were found in 40.6% of the tumor group and in none of the control group. Thus, deficits of the ABR threshold >30 dB ca n be considered to be an additional criterion for detecting retrocochlear d isease and increases ABR sensitivity for tumor detection even if responses are absent.