**6. Complications**

Cochlear implantation is generally a safe performed surgical procedure throughout the world with globally estimated complication rate of 16% [18]. Requiring additional surgery or cochlear explantation is categorized as major, and complications needing conservative medical management are classified as minor complications. Now, complication rates are decreasing due to improved experience, using smaller incisions and improvements in designing devices, and are generally calculated to be 11.8% for minor and 3.2% for major complications [27].

Infection is one of the most important major complications of cochlear implantation. Skin infection and acute otitis media are the most common type of implant-related infections ranging from 1 to 12% in the literature. Otitis media and soft tissue infection increase the risk of cochlear implant removal if leading to receiver stimulator infection. Also, it has been reported that cochlear implantation increases the risk of bacterial meningitis as 30-fold greater than general population; however, dawn of vaccination has made these cases sporadic [28]. Facial nerve palsy is another major complication of cochlear implantation, which is estimated to occur in 0.7% of cases due to heat induced by drill, cochleostomy, or reactivation of herpes virus as a result of surgery stress [29]. Finally, device failure is another major complication of cochlear implantation occurring in 2.5–6% of cases [18, 27]. Vestibular symptoms, such as vertigo and disequilibrium, are present in about one-third of patients postoperatively and are believed to last for more than 1 week after surgery. Most of these symptoms are resolved in weeks; however, patients over 70 years of age are more likely to have permanent vestibular weakness [30].

A proper localization involves a good bilateral hearing and sound stimulation, as well as intraaural time differences, which allow complex processing of sounds. Recent studies have mentioned some advantages for cochlear implantation in unilateral hearing loss, and some has reported a better sound localization in comparison with bone-anchored implants [54]. Additionally, it has been shown that cochlear implants resolve tinnitus up to an acceptable extent in patients with single-sided deafness and may improve speech perception [34, 55].

Cochlear Implants: An Excursus into the Technologies and Clinical Applications

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A hybrid cochlear implant was developed by Gantz et al. with the aim of preserving residual hearing, which has only 10 mm of height [56]. This provides the possibility for stimulating the region responsible for high-frequency hearing in cochlea without stimulating regions responsible for low frequency hearing. Primary studies have revealed that hybrid implant application is associated with better hearing preservation and increased speech perception [35, 36, 57, 58]. In addition to the comparable performance of hybrid implants with conventional ones, patients with hybrid implants had improved music appreciation as a result of acoustic and electrical stimulation combination [56, 57]. Replacement of hybrid implant with full-length implant in a progressive hearing loss improves hearing and word recognition; however, it is

Cochlear implantation has been utilized for Meniere's disease, a condition consisted of episodic attacks of tinnitus, hearing loss, and debilitating vertigo spells. Previous studies have shown resolution of related symptoms after cochlear implantation in Meniere's disease patients, although the hearing outcomes are not as acceptable as patients implanted for other

So far, some in vitro and animal studies have been conducted to resolve the hearing impairment problem using regenerative medicine; nevertheless, cochlear implantation remains as the most effective current treatment method. Further efforts are being put to cochlear implantation technology field in order to improve understanding speech in noise and music appreciations.

**8.2. Hybrid cochlear implants**

reasons [61, 62].

**Abbreviations**

CI cochlear implant

dBHL decibels hearing level

CROS contralateral routing of signal

associated with a notable additional cost [59, 60].

**8.3. Cochlear implantation and Meniere's disease**

**9. Prospective of cochlear implantation**
