Definition of COUNTERBORE. : to form a counterbore in: enlarge (part of a hole) by means of a counterbore.ADVERTISEMENT.efinition of COUNTERBORE. 1. : a flat-bottomed enlargement of the mouth of a cylindrical bore. 2. : a drill for making a counterbore â compare countersink.
The vestibulocochlear nerve (auditory vestibular nerve) , known as the eighth cranial nerve, transmits sound and equilibrium (balance) information from the inner ear to the brain.
*for accuracy, CN IV (the only cranial nerve that arises form the posterior cord) provides contralateral function. Because of its length and point of crossing, compression typically occurs after crossing, therefore, symptoms remain ipsilateral. This is rarely a significant CN to test in the critical care population.