Electrical Stimulation of the Auditory Nerve via Cochlear Implants in Patients with Auditory Neuropathy

Abstract

Auditory neuropathy (AN) is a term used to describe an auditory disorder in which there is evidence of normal outer hair cell function (otoacoustic emissions and/or cochlear microphonics) and poor function of the auditory nerve (absent or highly distorted auditory brain stem response starting with wave I). Many of these patients have evidence of generalized peripheral nerve disease, leading to an assumption that the peripheral portion of the auditory nerve is the most likely site of lesion. A small group of these patients has received cochlear implants, and the majority of them achieve average to above-average performance. Although this outcome may seem incongruous with neural disease, average performance by patients with AN may be a result of the reintroduction of neural synchrony by electrical stimulation and/or the fact that most deaf patients have poor nerve survival. Although cochlear implants are promising for deaf patients with AN, more study of the disorder is needed.

Eletrococleografia extratimpânica na neuropatia/dessincronia auditiva

“…When OAEs are absent in these patients, however, the differential diagnosis depends on CM recordings. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]20,21 It seems inappropriate to analyze CMs by using ABEP testing for the following reasons: the stimulus (click) that is used to initiate neural potentials limits the conditions for recording CMs; 1,20,25,34 and secondly, many clinicians perform ABEP testing with supra-aural phones,…”

“…Audiograms, when they can be applied, may be flat or show an upward or downward-sloping curve or be completely irregular; findings usually do not match speech understanding difficulties. 1,[11][12][13][14][15] It may be difficult to locate the injury site in AN/ AD, although the presence of OAEs and/or CMs suggests that outer hair cells (OHC) are intact. The ABEP wave I, however, which is generated by the myelin-sheathed peripheral portion of the cochlear nerve, is absent in this auditory condition.…”

Auditory neuropathy: Endocochlear lesion or temporal processing impairment? Implications for diagnosis and management

“…The basis of this phenotype is a length-dependent axonal degeneration, or a demyelinating neuropathy, although both pathologies co-exist in certain cases. Whilst the peripheral portion of the auditory nerve is the most likely site of lesion associated with the auditory symptoms [48], studies in Slovene, Italian and Bulgarian gypsy families have suggested a mutation in the chromosome 8 (genetic locus 8q24.3) inherited in an autosomal recessive pattern as the genetic basis of the associated AN/AD phenotype [49][50][51][52]. In addition, AN/AD also occurs in the most common form of the disease, the mutation in the genetic locus 17p11.2, inherited in an autosomal dominant fashion [53,54].…”

“…In theory, the electric signals from the cochlear implant may improve synchronization within the auditory pathway [48,[107][108][109], thus ameliorating temporal processing in AN/AD patients. The preoperative, intraoperative, and postoperative evoked potential measures show that the restoration of neural synchrony may actually occur at multiple levels of the auditory pathways in patients with AN/AD [110].…”

Auditory neuropathy/auditory dyssynchrony in children with cochlear implants

“…[1][2][3] Other communication strategies -communication by gestures, lip reading, and frequency modulated (FM) systems -have been suggested for habilitation and rehabilitation in this group of patients 4,5 . About one third of AN/AD patients present severe to profound hearing loss, and are thus candidates for cochlear implants 6 . Cochlear implants are indicated in this group because this electronic device can partially replace the function of auditory sensory cells.…”