The Cochlear Nuclei Revisited

The cochlear nuclei (CN) in man consist of the dorsal (DCN), superior ventral (SVCN), and inferior ventral (IVCN). The CN is located on the dorsolateral surface of the brain stem at the junction of the medulla with the pons. The DCN curves over the inferior cerebellar peduncle and forms part of its dorsolateral surface. The IVCN is found beneath the lateral portion of the DCN. The SVCN is for the most part covered by the inferior portion of the middle cerebellar peduncle. Of five types of nerve cells found in the CN in man, spheroid cells appear especially in the SVCN. They are the second-order neurons of the main ascending neural auditory pathway. Their injury forms the basis for hearing loss of central type. The SVCN can be mapped into estimated frequency strata progressing from low frequencies ventral to high frequencies dorsal. Spheroid cells are susceptible to injury notably by anoxia and especially centering around an estimated 4,000 Hz frequency level in the SVCN. The pattern of injury of spheroid cells can be displayed in comparison with audiometric tracing on a standard audiogram chart.