gms | German Medical Science

Objective: Brainstem auditory evoked potentials (BAEP) are the standard method for intraoperative montioring of the auditory nerve during surgical procedures in the cerebello-pontine angle (CPA). Amplitude and latency changes are utilized as warning signs for damage to the nerve and subsequent hearing loss. While many studies investigated relation of BAEP changes to preservation or loss of hearing, little data is available about prognostic value in regard to the postoperative hearing class.

Method: All patients who underwent BAEP-monitoring during intracranial surgery between Juli 2006 and April 2013 were included. BAEP amplitudes and latencies of wave I, III and V at the beginning and end of the surgical procedure were evaluated and related to pre- and postoperative AAO-HNS hearing class. BAEP had been recorded with a Nicolet Viking II- and a Natus Endeavor-system using Nicolet TIP-300 earphones. Procedures of auditory stimulation corresponded to clinical standards.

Results: A total of 65 patients were included. In 19 patients, BAEP amplitudes were too low for reliable latency estimation. In the remainder, latency changes of wave I, III and V did not reach a significant correlation to pre- vs. postoperative hearing class. BAEP amplitude deterioration however was related to postoperative hearing (r=0.62, 0.67 and 0.68 for wave I, II and V, p<0.0001, partial correlation, taking preoperative hearing class into account). Significant changes of any wave were observed with amplitude changes of <50%, amplitude changes over 50% were already associated with severe hearing impairment (class D or complete deafness). Maximal sensitivity and specificity (Youden’s index 0.77) was reached by stable waves III or V for hearing classes A or B (serviceable hearing). Best performance for predicting any hearing was reached by using any amplitude decrease of waves III or V as warning parameter (positive/negative predictive value 0.88/0.81). Preservation of a preoperative hearing class A was only poorly predicted (best performance: stable wave III or V, Youden’s Index 0.58).

Conclusions: BAEP amplitude deterioration is correlated to the postoperative hearing class. Best prediction performance is achieved by taking any amplitude decrease of wave III or V as warning sign for the loss of serviceable hearing. Preservation of a preoperative hearing class A is not detected reliably by BAEP.