Dexamethasone Is One of the Factors Minimizing the Inner Ear Damage from Electrode Insertion in Cochlear Implantation

Abstract

The aim of this study was to investigate the efficacy of preoperative and intraoperative steroid administration for inner ear protection in cochlear implantation (CI). Nineteen subjects who underwent CI were included in the study, and 10 subjects were enrolled as controls (steroid-administered group, n = 19; control group, n = 10). Dexamethasone (dexamethasone sodium phosphate, 5 mg/ml) was systemically administered preoperatively (1 ml) and topically applied during CI (0.5 ml). The extent of hearing preservation (HP) after CI and the change in the bithermal caloric response were evaluated. Hearing level was calculated using mean thresholds [(250 Hz + 500 Hz + 1,000 Hz + 2,000 Hz)/4]. Preoperative hearing thresholds were similar in the steroid-administered and control groups (100.92 ± 12.60 vs. 103.29 ± 14.39 dB, p = 0.650). The mean thresholds significantly increased in both groups after surgery (108.46 ± 14.08 dB, p = 0.006, for the steroid-administered group; 117.50 ± 6.34 dB, p = 0.027, for the control group), and the difference between the groups was also significant (p = 0.027). The postoperative shift in the hearing thresholds at frequencies of 500 and 1,000 Hz was significant in the steroid-administered group and that at the frequencies of 500, 1,000 and 2,000 Hz was significant in the control group. However, the extent of the shift in hearing threshold levels at each frequency was not significantly different between the groups. Preservation of hearing thresholds was compared between the groups, and there were significantly more subjects with complete and partial HP in the steroid-administered group than in the control group (p = 0.008). The preoperative caloric response was maintained after CI in the steroid-administered group. This study suggests that the perioperative use of a steroid could minimize the inner ear damage after CI.

The Role of Preoperative Steroids for Hearing Preservation Cochlear Implantation: Results of a Randomized Controlled Trial

“…The largest decline in hearing occurred within the first month after surgery, a result echoed by a recent study with a cohort having similar thresholds to ours [Cho et al, 2016]. In this study, the early decline was then followed by a more gradual decline.…”

“…The second was a randomized controlled trial that found topical steroids reduced vestibular symptoms [Enticott et al, 2011]. The third study found a combination of intravenous steroids 1 day and 1 h prior to surgery and then intraoperatively in the RW was shown to have better hearing preservation at 12 months compared to a control group [Cho et al, 2016]. However, this study involved a heterogeneous group with different electrodes, nonrandomization, nonblinding, different insertion techniques, and inconsistent followup between the 2 groups.…”

Long-Term in vivo Release Profile of Dexamethasone-Loaded Silicone Rods Implanted Into the Cochlea of Guinea Pigs

“…Many experimental studies in animals have demonstrated that the use of corticosteroids is able to preserve hearing thresholds, increase the survival of hair cells and spiral ganglia, and decrease the formation of new fibrotic tissue within implanted cochlea (20)(21)(22)(23)(24)(25)(26)(27). Clinical studies demonstrate lower impedances and improved preservation of low-frequency residual hearing in patients when corticosteroids are used in CI surgery (28)(29)(30)(31)(32)(33)(34). The efficacy is attributed to the anti-apoptotic and anti-inflammatory properties of glucocorticoids, by inhibiting immune cells and decreasing the release of inflammatory factors.…”

Steroid intracochlear distribution differs by administration method: Systemic versus intratympanic injection

“…Steroids effectively preserve hearing in the basal region (which detects high‐frequency sound) . However, residual hearing in cochlear implantation candidates is largely confined to the apical area (which detects low‐frequency sound) . Drug distribution along the length of the cochlea is determined principally by the rate of drug diffusion relative to that of drug clearance from the scala .…”

“…10,24 However, residual hearing in cochlear implantation candidates is largely confined to the apical area (which detects lowfrequency sound). 25,26 Drug distribution along the length of the cochlea is determined principally by the rate of drug diffusion relative to that of drug clearance from the scala. 15 Eastwood et al suggested that the extent of hearing protection in the second turn was greater when a higher steroid concentration was used.…”