Abstract
The aim of this study was to investigate the effects of intracochlear bleeding during cochleostomy on cochlear inflammatory response and residual hearing in a guinea pig animal model. Auditory brainstem response threshold shifts were greater in blood injected ears (p<0.05). Interleukin-1β, interleukin-10, tumor necrosis factor-α and nitric oxide synthase 2, cytokines that are related to early stage inflammation, were significantly increased in blood injected ears compared to normal and cochleostomy only ears at 1 day after surgery; with the increased IL-1β being sustained until 3 days after the surgery (p<0.05). Hair cells were more severely damaged in blood injected ears than in cochleostomy only ears. Histopathologic examination revealed more extensive fibrosis and ossification in blood injected ears than cochleostomy only ears. These results show that intracochlear bleeding enhanced cochlear inflammation resulting in increased fibrosis and ossification in an experimental animal model.
Highlights
Cochlear implant surgery is a widely used surgical procedure done to restore hearing in patients with severe and profound hearing loss
IL-1β, IL-10, tumor necrosis factor-α (TNF-α), and nitric oxide synthase 2 (NOS 2) were significantly increased in blood injected ears compared to the normal and control ears at 1 day after surgery
The results showed that IL-1β, IL-10, TNF-α, and NOS 2 were significantly increased in blood injected ears on the first day after surgery compared to control ears
Summary
Cochlear implant surgery is a widely used surgical procedure done to restore hearing in patients with severe and profound hearing loss. Residual hearing is immediately preserved after cochlear implantation especially with the development of soft surgery or the round window approach[1, 2]. It has been reported that approximately one third of cochlear implant recipients would slowly lose their residual hearing over the few months[3,4,5,6]. In a postmortem human temporal bone study of cochlear implantation, the auditory threshold levels were increased with greater amount of intracochlear fibrosis and ossification[7,8,9]. The ensuing fibrosis and ossification in the cochlea may account for the delayed hearing loss following cochlear implantation. The reasons for this phenomenon are not well understood, the tissue response to implantation may be implicated[10,11,12,13,14]
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