![]() Many subjects with ANSD have hearing loss and/or speech perception deficits severe enough that treatment with a cochlear implant (CI) is indicated. Proposed sites of lesion include the inner hair cells (IHCs), the synapse between the IHCs and the type I afferents of the auditory nerve, the auditory nerve itself, and the synapse between the auditory nerve fibers and their targets in the cochlear nucleus ( Starr et al., 1996 Doyle et al., 1998 Zeng et al., 1999 Berlin et al., 2003 Fuchs et al., 2003 Rapin and Gravel, 2003). A wide range of etiologies and associations for ANSD has been identified, including perinatal hyperbilirubinemia, mechanical ventilation, infection (measles, mumps), mutations in the otoferlin gene and cochlear nerve deficiency ( Starr et al., 2001 Varga et al., 2003 Buchman et al., 2006 Bielecki et al., 2012). Relatively healthy hair cells are identified by the presence of otoacoustic emissions (OAEs) and/or cochlear microphonic (CM) in ABR testing, coupled with small or absent wave V ( Kaga et al., 1996 Starr et al., 1996 Berlin et al., 1998 Rance et al., 1999 Teagle et al., 2010). However, the clinical tests do not capture the wide range of neural activity seen to low frequency sounds.Īuditory neuropathy spectrum disorder (ANSD) is a hearing dysfunction characterized by an apparent discrepancy between the measures of cochlear and neural function when viewed by surface electrode auditory brainstem response (ABR) testing. These results indicate that responses to high frequencies, derived primarily from hair cells, are the main source of the CM used to evaluate ANSD in the clinical setting. Common morphologies in other groups were either only a CM, or a combination of CM and CAP. ![]() To high frequencies, the common morphology of ANSD cases was a large CM and summating potential, and small or absent CAP. However, nerve scores of the ANSD group were similar to the other cohorts, although dominated by the ANN to low frequencies more than in the non-ANSD groups. ![]() Subjects identified as ANSD (45 ears in children, 3 in adults) had higher values of ECochG-TR than adult and pediatric subjects also receiving CIs not identified as ANSD. Magnitudes of the responses to tones of different frequencies were summed to measure the “total response” (ECochG-TR), a metric often dominated by hair cell activity, and auditory nerve activity was estimated visually from the compound action potential (CAP) and auditory nerve neurophonic (ANN) as a ranked “Nerve Score”. To better understand the cochleae identified with ANSD that lead to a CI, we performed intraoperative round window electrocochleography (ECochG) to tone bursts in children ( n = 167) and adults ( n = 163). Many identified ANSD patients have speech impairment severe enough that cochlear implantation (CI) is indicated. Clinical indicators of ANSD are a present cochlear microphonic (CM) with small or absent wave V. Louis, MO, United StatesĪuditory neuropathy spectrum disorder (ANSD) is characterized by an apparent discrepancy between measures of cochlear and neural function based on auditory brainstem response (ABR) testing. 4Department of Otolaryngology/Head and Neck Surgery, Washington University School of Medicine in St. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |