ABR is an objective test of hearing that records the activity of both the vestibulocochlear cranial nerve and central nervous system in response to an auditory stimulus. It is often part of the evaluation in patients who are difficult to test (i.e. newborns, infants, and adults with suspected non-organic hearing loss) or as part of intraoperative monitoring of the cochlear nerve (i.e. hearing preservation surgery for vestibular schwannoma). There is an automated ABR test which removes the need for interpretation by the tester. It is used mainly for screening purposes. Many healthcare systems around the world have set up a newborn hearing screening programme that includes ABR, first used for this purpose in 1979. ABR can provide ear-specific and frequency-specific thresholds. The stimulus is called a click, and it consists of very short pulses presented at different frequencies. Electroencephalogram (EEG) activity is measured to see the corresponding waves generated after each click. The waveforms are known to change with the maturation of the auditory system; newborns tend to have more prominent waves I, III and V, while in adults the most prominent wave is V.