Middle latency electric auditory responses in patients with acoustic neuroma

Simultaneous evaluation of auditory brain stem response (ABR) and middle latency response (MLR) in groups of adult subjects with normal hearing, sensorineural hearing loss, and internal auditory canal (IAC) and cerebellopontine angle (CPA) tumors was carried out. Middle latency response delays similar to those described for ABR are seen in patients with IAC and CPA tumors, and such abnormalities are not seen in patients with sensorineural hearing loss from other causes. In comparison with the ABR in tumor patients, the MLR can be evoked more often but the percentage of false negative responses (based on peak latency values) is higher. Using a compound stimulus strengthens the test by allowing examination of more peaks.