Auditory development of children

The measured auditory development of children is a series of six to seven vertex positive waves of which I through V are evaluated. In 1967, Sohmer and Feinmesser were the first to publish ABRs recorded with surface electrodes in humans which showed that cochlear potentials could be obtained non-invasively.

In 1971, Jewett and Williston gave a clear description of the human ABR and correctly interpreted the later waves as arriving from the brainstem. The ABR represents initiated activity beginning at the base of the cochlea and moving toward the apex over a 4ms period of time. The ABR is used for newborn hearing screening, auditory threshold estimation, intraoperative monitoring, determining hearing loss type and degree, and auditory nerve and brainstem lesion detection, and in development of cochlear implants. One use of the traditional ABR is site-of-lesion testing and it has been shown to be sensitive to large acoustic tumors. However, it has poor sensitivity to tumors smaller than 1 centimeter in diameter.

In the 1990s, there were several studies that concluded that the use of ABRs to detect acoustic tumors should be abandoned. The reason the ABR does not identify small tumors can be explained by the fact that ABRs rely on latency changes of peak V . Peak V is primarily influenced by high-frequency fibers and tumors will be missed if those fibers aren’t affected. Although the click stimulates a wide frequency region on the cochlea, phase cancellation of the lower frequency responses occurs as a result of time delays along the basilar membrane. Primary reasons why it is not practical to simply send every patient in for an MRI are the high cost of an MRI, its impact on patient comfort, and limited availability in rural areas and third-world countries. Manuel Don and colleagues published on the Stacked ABR as a way to enhance the sensitivity of the ABR in detecting smaller tumors.

Their hypothesis was that the new ABR-stacked derived-band ABR amplitude could detect small acoustic tumors missed by standard ABR measures. The stacked ABR is the sum of the synchronous neural activity generated from five frequency regions across the cochlea in response to click stimulation and high-pass pink noise masking. The development of this technique was based on the 8th cranial nerve compound action potential work done by Teas, Eldredge, and Davis in 1962. When the derived waveforms are representing activity from more apical regions along the basilar membrane, wave V latencies are prolonged because of the nature of the traveling wave.