Effect of surgical drilling on cochlear potentials

The aim of the experiment was to examine the effect of
noise and mechanical vibrations generated during the drilling of the bones
surrounding the cochlea on the cochlear microphonics (CM). The experiment was
carried out on a group of 40 guinea pigs divided equally into a group to be
studied and a control group. In the studied group, CM values were measured three
times: immediately after opening the bulla, after 30 minutes of nonstop drilling
and two hours later, whereas in the control group they were measured twice:
immediately after opening the bulla and 2.5 hours later. In this way the
post-drilling shock and the long-term injuries to the cochlea could be studied.
A statistical analysis of the obtained results shows that surgical drilling may
cause an average decrease of 50-60% in CM values in comparison with the control
group.