Brainstem auditory evoked potentials (BAEPs) testing is very important when microvascular decompression (MVD) is performed with hemifacial spasm (HFS). The reason for this is that the vestibulocochlear nerve is located right next to the facial nerve, so the vestibulocochlear nerve may be affected by manipulation by surgery. The BAEPs test method for detecting vestibulocochlear nerve damage during surgery has been developed a lot and is helping a lot during surgery. In most HFS patients with normal vestibulocochlear nerve, the degree of vestibulocochlear nerve damage caused by surgery is reflected very well in the BAEPs test waveforms. Therefore, a real time test is the best way to minimize the damage to the vestibulocochlear nerve. The purpose of this study was to review the most recently published BAEPs test used in MVD surgery and to find out in detail the relationship between the vestibulocochlear nerve damage and the BAEPs waveforms.