The surgical strategy in tumors located in the cerebello-pontine angle involves minimal
manipulation of the cranial nerves and brain stem. In fact, the manipulation of these
structures and any eventual damage to them are the most important factors associated
with postoperative functional outcome and quality of life. Intraoperative electrophysiological
monitorization (IOM) is essential to minimize the manipulation to these structures.
Nevertheless, little data are available regarding the efficacy of IOM in preventing
functional deficits.
Aim: To calculate the risk of hearing deterioration as a function of changes in the amplitude
and latency of the most stable components of the auditory evoked potential (AEP) during
surgery (waves III and V).
Method: In a consecutive series of 40 patients who had surgically treated petroclival meningiomas,
the results of intraoperative ABR monitoring and the hearing status of each patient
before and after surgery were retrospectively analyzed. A mathematical analysis was
performed to define the most sensitive and specific way to predict hearing dysfunction
after surgery.
Results: The mean age of the sample was 59 ± 10 years with 31 female and 9 male patients.
Twelve patients out of 40 presented preoperatively with clinically detectable hearing
impairment. In the first assessment (prior to hospital discharge after surgery), eight
patients presented deterioration of hearing function; four of them reported subjective
improvement. Among those 8 who reported initial deterioration, 4 recovered until the
last assessment and 4 remained stable. The predictive value of each electrophysiological
parameter was examined based on a Receiver Operating Characteristic analysis. As related
to wave III latency, the measurement reached its highest specificity and sensitivity
at the value x = 143%. At this level, the calculated sensitivity was 71.43% and the
specificity was 100%. In a similar manner, the highest sensitivity and specificity
for the latency of wave V were 71.43% and 92.86%, respectively, at x = 124%. For the
amplitude of wave V, we calculated the sensitivity to be 100%, and the specificity
was 78.57% for x = 74%.
Conclusions: Intraoperative alterations of wave III latitude and wave V amplitude seem to constitute
a highly sensitive and specific method to predict the risk of auditory dysfunction,
contributing to the maximum extension of resection with the preservation of function.
