Cochlear implantation in rats: A new surgical approach

Abstract

The laboratory rat has been used extensively in auditory research but has had limited use in cochlear implant related research due mainly to the surgically restricted access to the scala tympani. We have developed a new surgical method for cochlear implantation in rats. The key to this protocol was cauterizing the stapedial artery (SA) and making a small cochleostomy near the round window in order to enlarge the surgical access to the scala tympani. Five normal hearing Hooded Wistar rats were used to investigate the effect of cauterizing the SA on hearing and auditory nerve survival. Results showed that cauterizing the SA was surgically feasible, afforded excellent exposure of the round window niche for cochleostomy, and did not adversely affect acoustic thresholds measured electrophysiologically. Moreover, there was no difference in spiral ganglion cell densities for any cochlear turn when compared with the contralateral control ears. Three deafened rats were subsequently implanted with a scala tympani electrode array using this new surgical approach. Electrically evoked auditory brainstem responses using bipolar stimulation, and subsequent cochlear histopathology demonstrated that the cochlear implantation using a custom-made rat electrode array was safe and effective. The surgical approach presented in this paper presents a safe and effective procedure for acute or chronic cochlear implantation in the rat model.

Cochlear implantation for chronic electrical stimulation in the mouse

“…We have also provided evidence that corroborates previous research showing that cauterizing the SA in small rodents with a prominent SA has no significant effect upon hearing thresholds or SGN counts (Lu et al, 2005;Emadi et al, 2004). In a clinical setting there is evidence of hearing loss associated with this procedure (Schuknecht, 2010).…”

“…overlying the RW niche, has shown no adverse effects on hearing thresholds or spiral ganglion neuron survival (SGN; Lu et al, 2005). In order to determine the effects of cauterizing the SA on hearing thresholds and SGN survival in the mouse, the SA was cauterized in 5 animals.…”

“…In order to determine the effects of cauterizing the SA on hearing thresholds and SGN survival in the mouse, the SA was cauterized in 5 animals. The surgical approach was similar to that described in the rat by Lu et al (2005): the bullostomy was drilled as above, the SA was then cauterized within the bulla using bipolar cautery forceps. The bulla was then closed with sterile polycarboxylate cement (Durelon, ESPE, Norristown, USA), and the wound closed in two layers using an absorbable 6/0 suture.…”

“…To date, no method has enabled the delivery of chronic electrical stimulation to the mouse cochlea, primarily due to the absence of a reliable electrode-stimulator assembly small enough for chronic murine use, and the difficulty of the implantation surgery in such a comparatively small cochlea. To compound this surgical difficulty, the mouse, like the rat (Lu et al, 2005), has a stapedial artery (SA) that runs inside the middle ear cavity close to the round window (RW) niche, reducing surgical access to the cochlea and increasing surgical risk.…”

Study of mouse induced pluripotent stem cell transplantation intoWistar albino rat cochleae after hair cell damage*

“…After drilling of the right otic bulla, the stapedial artery and the basal turn of the cochlea were identified ( Figure 1c). Cochleostomy was performed right afterwards (12). The solution containing IPSCs (30 × 10 5 cells, 10 µL DMEM) was injected at a speed of 1 µL/min.…”