Cochlear implantation in patients with a history of chronic otitis media

OBJECTIVE: To propose management options for cochlear implantation in chronic otitis media based on our experiences. MATERIAL AND METHODS: A retrospective review of 418 cochlear implantations performed by the 2 senior authors between November 1988 and February 2004 was conducted. Nine patients who had chronic otitis media in the ear to be implanted were included. Of these, three showed active inflammation at presentation; the other six cases had undergone previous tympanomastoidectomy surgery and did not show active inflammation at presentation. RESULTS: Five patients with active inflammation or without an adequate soft tissue layer in the mastoid bowl underwent a two-stage procedure. Four cases who showed inactive inflammation and had an adequate tissue layer to protect the electrode array underwent a single-stage technique, although two of them showed dry tympanic membrane perforation. No local or intracranial inflammation recurred. The electrode was exposed in the mastoid bowl in one case, who was managed with revisional mastoid obliteration with soft tissue. CONCLUSION: Complete eradication of inflammation and the securing of a strong protective soft tissue layer over the electrode are prerequisites for cochlear implantation in ears with chronic otitis media.     

Management options for cochlear implantation in patients with chronic otitis media

ObjectivePatients with chronic otitis media with/without cholesteatoma present a significant challenge to safe cochlear implantation (CI). The aim of our study is to describe our experience and propose management options for CI in patients with chronic otitis media.Study designRetrospective case study.SettingTertiary academic center.Subject and methodsWe enrolled the 9 ears of 8 subjects who received CI in the ear with chronic otitis media from 2006 to 2013 by a single surgeon. CI was performed as a single-stage or staged operation with mastoid surgery according to the activity of ear infection.ResultsSix patients had bilateral chronic otitis media and 2 patients had long history of sensorineural hearing loss at contralateral ear. CI was performed with simultaneous radical mastoidectomy with closure of the EAC as a single-stage in 3 ears with a history of previous open cavity mastoidectomy and no active discharge. Staged CI was performed in 6 ears, after radical mastoidectomy with closure of the EAC in 3 ears and after intact canal wall mastoidectomy in 3 ears, due to active inflammation or complications related to otitis media. In one patient, wound infection had occurred, and implant was removed along with implantation at contralateral ear. Other subjects showed no evidence of recurrence.ConclusionDecision whether implantation as a single-stage or staged operation depends on the presence of active inflammation. Single-stage CI with proper mastoid surgery can be performed in patients without active inflammation. Staged procedure need to be done in ears with active inflammation. Proper application of mastoid surgery leads to safe CI for patients with chronic otitis media.     

Contemporary surgical issues in paediatric cochlear implantation

Abstract

Objective: To review the contemporary surgical issues in paediatric cochlear implantation (CI) based on published evidence. Design: Narrative literature review. Results: Surgical challenges in paediatric CI are discussed, with respect to post meningitic labyrinthitis ossificans; cochlear malformation; cochlear implantation in infants; auditory neuropathy and cochlear nerve deficiency; bilateral cochlear implantation; hearing preservation; otitis media; and device failure. Conclusion: Early CI is recommended if bacterial meningitis causes profound sensorineural hearing loss (SNHL). CI in cochleovestibular malformation requires pre-operative imaging to plan surgical technique, choice of electrode, and to anticipate complication. Children with congenital severe to profound SNHL should undergo early bilateral simultaneous implantation, preferably before 12 months of age, except those with auditory neuropathy spectrum disorder who should be implanted after one year. Soft surgical technique should be deployed in an attempt to preserve any residual hearing. Otitis media with effusion is not a contraindication to cochlear implantation, but active or recurrent acute otitis media requires resolution of infection with grommet insertion pre-operatively. Device failure in CI recipients requires a stepwise audiological, medical, radiological, and device integrity assessment to determine the need for reimplantation.     

Recurrent cochlear implant infection treated with exteriorization and partial mastoid obliteration

Objective and importance: Preoperative chronic otitis media (COM) is a risk factor for postoperative infection after cochlear implantation (CI), but its management varies by surgeon. Our case highlights a strategy for implant preservation in a patient with a history of recurrent cochlear implant infection.

Clinical presentation: A 70-year-old woman with a history of chronic lymphocytic leukemia presented in 2005 with bilateral COM and sensorineural hearing loss meeting CI candidacy. Four months after left mastoid obliteration with abdominal fat graft and external auditory canal closure, a left CI was placed. Subsequent postauricular cellulitis resolved with oral antibiotics. A similar two-stage CI was performed on the right without complication. During the following year, numerous left-sided infections and fluid collections developed but were treated unsuccessfully with intravenous (IV) antibiotics and operative debridement. With concern for biofilm colonization, the implant was explanted and the electrode left in the cochlea. After reimplantation in 2010, infections resumed despite long-term IV antibiotics and incision and drainage.

Intervention and technique: In 2012, the left mastoid cavity was exteriorized and converted to standard canal wall-down anatomy. Bone pâté was placed over the electrode, followed by cadaveric acellular dermis and a split-thickness skin graft. After more than 2 years, her better-performing CI remains infection-free.

Conclusion: After 6 years of postoperative infections unresponsive to aggressive medical management, surgical interventions, and period of device removal, our patient's infections resolved after mastoid exteriorization and multilayered protection of the electrode. This strategy may enable implant preservation in patients with recurrent post-CI infection in an obliterated cavity.     

Chronic inflammatory reaction to bone wax in cochlear implantation: A case report and literature review

Background: Cochlear implantation is a well-established treatment for severe-to-profound sensorineural hearing loss. While bone wax is used commonly during mastoidectomy and other bony surgeries as a hemostatic agent, there have been reports of bone wax triggering foreign body reactions, months to years after surgery. This report describes the first known foreign body reaction to bone wax used in cochlear implantation surgery.

Case Presentation: A 6-year-old male presented with an unusual post-auricular inflammation two years after cochlear implantation. Extended treatment with oral and intravenous antibiotics failed to resolve the presumed infection. Upon exploration of the mastoid cavity, fragments of bone wax were discovered within the granulation tissue. Excision of bone wax fragments and local flap reconstruction resulted in complete resolution of the inflammatory process.

Conclusions: Bone wax has been implicated in foreign body reactions in many different surgical specialties. This is the first reported case of an adverse reaction to bone wax after cochlear implantation. Clinically, the bone wax reaction was misinterpreted as an implant infection, which resulted in extended antibiotic use and delay of appropriate treatment. As a result, bone wax should be used judiciously during mastoidectomy, and particularly in the area of the electrode and soft tissue closure.     

中耳炎性病变患者的人工耳蜗植入

目的探讨伴中耳炎性病变的患者进行人工耳蜗植入的适应证、手术方法和术后并发症的发生情况。方法对1995年5月至2006年2月完成的866例人工耳蜗植入术的临床资料进行回顾性分析。术前或术中发现伴中耳乳突炎性病变患者共41例，其中男17例，女24例，年龄1岁3个月-38岁，平均10岁2个月；左耳人工耳蜗植入18例，右耳植入23例，均为单侧植入。其中慢性分泌性中耳炎13例，隐蔽性中耳炎18例，中耳炎后遗症鼓膜穿孔1例，双侧胆脂瘤中耳炎2例，中耳乳突肉芽肿7例。中耳炎性病变伴内耳、中耳畸形7例。对于双侧胆脂瘤中耳炎乳突根治术后患者，设计采用了带蒂翻转帽状腱膜法保护植入电极和面神经。结果41例患者经 Ⅰ期或分期手术，术后随访时间5个月至6年11个月，平均未发现耳部炎性并发症，装置工作良好。结论慢性非化脓性中耳炎、中耳乳突肉芽肿、中耳炎后遗症伴鼓膜穿孔者可采用Ⅰ期或分期方法行人工耳蜗植入。胆脂瘤中耳炎在彻底去除病变基础上可分期行人工耳蜗植入术。对于乳突根治术后没有足够组织覆盖保护植入电极的病例，可采用带蒂翻转帽状腱膜方法。存在活动性中耳乳突炎症者为手术禁忌证。中耳炎性病变患者人工耳蜗术后应长期随访。     

中耳乳突炎性改变对人工耳蜗置入的影响

目的：探讨中耳乳突炎性改变对人工耳蜗置入术的影响。方法：9例行人工耳蜗置入术患者均伴有中耳乳突炎性改变。1例乳突根治术后Ⅱ期行人工耳蜗置入及应用耳廓软骨一软骨膜复合物重建并加强后鼓室外侧壁及外耳道后壁;1例慢性中耳炎伴鼓膜穿孔Ⅰ期行人工耳蜗置入及应用耳廓软骨一软骨膜复合物重建鼓膜;3例隐性中耳乳突炎,Ⅰ期行改良乳突开放术并人工耳蜗置入术;3例硬化型乳突伴鼓室粘连,Ⅰ期行鼓室探查并人工耳蜗置入术;1例慢性中耳乳突炎伴松弛部内陷袋形成,Ⅰ期行上鼓室开放及软骨一软骨膜复合物重建上鼓室外侧壁并人工耳蜗置入术。结果：术中所有的电极均顺利置入,并经术中检测电极完好,电阻测试效果满意。术后伤口均甲级愈合,1个月后均开机成功。随访无并发症。结论：对于慢性中耳乳突炎的患者,若欲行Ⅱ期人工耳蜗置入术,Ⅰ期中耳乳突手术应尽可能保留相关解剖结构。对于隐性中耳乳突炎的患者在确保鼓窦乳突、上鼓室、咽鼓管口三处引流均通畅的前提下可行Ⅰ期人工耳蜗置入。对于病变局限的上鼓室胆脂瘤,有经验的术者可以选择Ⅰ期手术,但一定要慎重。感染因素很可能在乳突汽化不良及不明原因先天性感音神经性聋的发病中起着重要的作用。对于乳突硬化、乙状窦前移严重的患者可选择经外耳道鼓岬开窗。对于人工耳蜗置入术时的鼓膜修补术,上鼓室外侧壁或外耳道后壁重建选择软骨一软骨膜复合物可以提高成功率,加固鼓膜避免内陷及电极脱出。     

Cochlear implantation in patients with chronic otitis media

Objective

Patients with complications of otitis media present a significant challenge to safe cochlear implantation. We describe our experience of cochlear implantation in patients with chronic ear disease, and propose management principles according to the presenting status of the ear.

Methods

Cochlear implantations were performed as treatment for complications of otitis media in seven patients. They consisted of four patients with adhesive otitis media, two patients with an open cavity after surgery for otitis media and one patient with eosinophilic otitis media.The electrodes were inserted by an approach via the external auditory canal in patients with poor growth of the mastoid antrum or adhesion of the tympanum. For the patients with an open cavity, we created a posterior wall for the external auditory canal and perform the mastoid obliteration. Modified Rambo's technique with blind sac closure of the external auditory canal was performed for the case of eosinophilic otitis media as a single-stage procedure.

Results

The post-operative courses were good. However, a post-operative infection developed in one patient who had previously undergone radiation therapy following surgical excision of a cerebellar tumor.

Conclusion

Transcanal approach is effective in a poorly pneumatized mastoid or severe adhesive otitis media.A decision whether implantation as a single-stage or multiple stages depends on the condition of each cases. But there is a possibility of infection even if we selected a stage operation.     

Indications for and outcomes of mastoid obliteration in cochlear implantation.

OBJECTIVE: To review the indications, efficacy, and long-term outcomes of mastoid obliteration in cochlear implant surgery. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Seventeen patients who underwent a mastoid obliteration procedure to facilitate the insertion of a cochlear implant between 1978 and 2005. INTERVENTION: Mastoid obliteration procedure before cochlear implantation. MAIN OUTCOME MEASURES: Revision rate of the mastoid obliteration and cochlear implantation, postoperative audiometric scores (consonant-nucleus-consonant words/phonemes, Central Institute for the Deaf sentences, City University New York sentences in quiet and in noise), and incidence of complications. RESULTS: There were 17 patients with a median age of 60 years (range, 3-79 yr). Eight patients required mastoid obliteration for active chronic suppurative otitis media before cochlear implantation. Another 8 patients had existing mastoid cavities requiring obliteration (modified radical [n = 5] and fenestration cavities [n = 3]). A single patient with a sclerotic mastoid and an anterior sigmoid sinus underwent obliteration because of inadequate surgical access. The technique of obliteration was radical mastoidectomy with eustachian tube occlusion, blind sac closure of the external auditory canal, and cavity obliteration with either temporalis muscle flap (n = 15) or abdominal fat (n = 2). Cochlear implantation and mastoid obliteration were performed as a two-stage procedure in 10 patients and as a single-stage procedure in 7. Two patients required revision of the mastoid obliteration. At follow-up, all patients had stable obliterated cavities. Fifteen patients obtained significant improvement in speech discrimination scores, whereas 2 patients obtained some benefit from the cochlear implant through the perception of environmental sounds. CONCLUSION: For patients with chronic suppurative otitis media or existing mastoid cavities, the obliteration with temporalis muscle or abdominal fat is an effective technique to facilitate safe cochlear implantation.     

Is mastoidectomy indispensable in cochlear implant surgery?

OBJECTIVE: To challenge the need for mastoidectomy in cochlear implant (CI) surgery by comparing the advantages and disadvantages of the classic technique for CI, the mastoidectomy posterior tympanotomy approach (MPTA), with the suprameatal approach (SMA), a nonmastoidectomy approach. STUDY DESIGN and SETTING: A retrospective study of 290 patients who underwent cochlear implantation in our department between 1989 and 2002. One hundred fifty-seven of them underwent the MPTA and 133 underwent the SMA. The ability of the electrode to expand in the MPTA patients who were reoperated on was examined, as was the influence of mastoidectomy on the course of chronic secretory otitis media (SOM) in a group of 56 children who suffered from chronic SOM prior to implantation. RESULTS: In all 4 reoperated children, in whom the MPTA was used, the mastoid was completely closed by bony regrowth on the cortical portion of the mastoid and the mastoid cavity was obliterated. The electrode had been embedded in dense fibrous tissue and bony spicule, preventing electrode expansion. Mastoidectomy was found to have no influence on the course of chronic SOM. The rate of postoperative SOM was found to be equal in 40 children who were operated on using the MPTA compared with 16 operated on using the SMA. CONCLUSION: Using a nonmastoidectomy approach, such as the SMA, provides a wide exposure of the middle ear and promontory and thus enables a well-controlled cochleostomy site and safe insertion of the electrode into the cochlea. Mastoidectomy in CI surgery is not indispensable; it may cause more disadvantages than advantages.     

Acute mastoiditis in children with a cochlear implant

ObjectivesCochlear implantation is performed at a young age, when children are prone to acute otitis media. Acute mastoiditis is the most common complication of otitis media, but data on its management in the presence of a cochlear implant are sparse. The objective of this study was to assess the characteristics, treatment, and outcome of acute mastoiditis in children with a cochlear implant.MethodsThe medical files of all children who underwent cochlear implantation at a pediatric tertiary medical center in 2000–2014 were retrospectively reviewed. Those diagnosed with acute mastoiditis after implantation were identified, and data were collected on demographics, history, presentation, method of treatment, complications, association with untreated otitis media with effusion, and long-term middle-ear sequelae.ResultsOf the 370 children (490 ears) who underwent cochlear implantation, 13 (3.5%) were treated for acute mastoiditis (median age at acute mastoiditis, 32 months). Nine had a pre-implantation history of chronic secretory or acute recurrent otitis media, and 5 had been previously treated with ventilation tubes. In all 9 children who had unilateral cochlear implant, the acute mastoiditis episode occurred in the implanted ear. The time from implantation to mastoiditis was 5–61 months. The same treatment protocol as for normal-hearing children was followed, with special attention to the risk of central nervous system complications. Primary treatment consisted of myringotomy with intravenous administration of wide-spectrum antibiotics. Surgical drainage was performed in 8 out of 13 patients, with (n = 7) or without (n = 1) ventilation-tube insertion, to treat subperiosteal abscess or because of lack of symptomatic improvement. There were no cases of intracranial complications or implant involvement or need for a wider surgical approach. No middle-ear pathology was documented during the average 3.8-year follow-up.ConclusionsThe relatively high rate of acute mastoiditis and subperiosteal abscess in children with a cochlear implant, predominantly involving the implanted ear, supports the suggestion that recent mastoidectomy may be a risk factor for these complications. Despite the frequent need for drainage, more extensive surgery is usually unnecessary, and recovery is complete and rapid. As infections can occur even years after cochlear implantation, children with otitis media should be closely followed, with possible re-introduction of ventilation tubes.     

Tuberculous otitis media –series of 10 cases

BackgroundTuberculosis (TB) of the middle ear cleft (MEC) is a rare extra-pulmonary manifestation. Signs and symptoms of tuberculous otitis media are indistinguishable from that of non-tuberculous otitis media making early diagnosis difficult.ObjectivesTo study the clinical presentations, complications and effective diagnostic modalities in tuberculosis of middle ear cleft.MethodsWe retrospectively studied 10 patients diagnosed with chronic otitis media, unresponsive to 2 months conventional treatment. Pure tone audiogram, High resolution computed tomography (HRCT) of temporal bone, and AFB staining of ear discharge were done. All patients underwent mastoid surgery. AFB staining and histopathological examination of granulation tissue removed from the middle ear and mastoid were also done.ResultsClinical findings were mastoid swelling, facial palsy and post-aural fistula 3,4 & 2 patients respectively. All patients had persistent ear discharge and three had vertigo. Hearing loss was of moderate conductive type in five, sensorineural type in three and mixed type in two. HRCT of temporal bone revealed soft tissue density in MEC in 9 and evidence of bone destruction in 6 cases. Diagnosis of TB was confirmed either by (a) demonstration of AFB in ear discharge (4 patients)/tissue removed during surgery (4 patients) or (b) by demonstration of tuberculous granulomas with necrosis on histopathological examination of tissue from MEC (8 patients).ConclusionTuberculosis should be suspected in all cases of chronic otitis media unresponsive to conventional treatment particularly in endemic areas. Histopathological examination and AFB staining of tissue removed during mastoid surgery are reliable diagnostic methods.     

Chronic suppurative otitis media following paediatric cochlear implantation

Abstract

The objective of this study was to report and discuss the management of chronic suppurative otitis media (CSOM) following cochlear implantation in children. The study was a retrospective review of 650 patients receiving an implant at two paediatric tertiary referral centres for cochlear implantation. Nine patients were identified who developed CSOM following cochlear implantation (incidence 1.38%). The mean time interval between implantation and symptom development was 3.66 years (range 2–8 years) and the mean time interval between implantation and CSOM surgery was 5.02 years (range 2.2–8 years). All patients presented with otorrhoea and/or abscess formation over the implant site. Two patients underwent a modified radical mastoidectomy and seven underwent a combined approach tympanoplasty, three of whom required posterior canal wall reconstruction with cortical bone and one with cartilage. In four cases it was possible to remove the cholesteatoma without removing the implant. All but two patients were fitted with a contralateral implant. In the explanted ears the cochlear implant electrode was cut at the cochleostomy site, which was then covered with muscle. Chronic suppurative otitis media following cochlear implantation may occur either as a result of a posterior canal wall defect related to surgery or possibly de novo. Attempts should be made to save the implant, but explantation with reimplantation of the contralateral ear may be the only option. In these cases the intracochlear part of the electrode array should be left in situ to facilitate possible future reimplantation. Surgical options for management of CSOM should be individualized and may include both canal-wall up and canal-wall down techniques. To reduce the incidence of CSOM following implantation the authors recommend: (1) prompt treatment and careful follow-up of patients with a history of otitis media with effusion, (2) avoidance of excessive thinning of the posterior canal wall during mastoidectomy and (3) reconstruction of any accidental trauma to the annulus or posterior canal wall during posterior tympanotomy. Copyright © 2006 John Wiley & Sons, Ltd.     

Cochlear implantation in atelectasis and chronic otitis media: long-term follow-up.

OBJECTIVE: To report the long-term results of cochlear implantation in cases with chronic otitis media or atelectasis using a single surgical technique performed in a single cochlear implant center. PATIENTS: Nine patients who were implanted using the blind-pit closure of the external ear canal technique (4 patients with adhesive otitis media and 5 with radical mastoid cavities). Follow-up ranged from 18 months to 12 years (mean, 7.05 yr). INTERVENTION: The surgical procedure was performed in 2 stages. The first stage included canal wall down or lowering any high facial ridge in previous mastoidectomies, removal of all skin, and blind-pit closure of the external ear canal without mastoid cavity obliteration or eustachian tube obliteration. Cochlear implantation was performed 6 months after the first surgical procedure. RESULTS: All operations were uneventful, and during cochlear implantation, as a second stage, no epithelia or other problems were encountered. No serious complications were encountered during the follow-up period. One case had a minor disruption of the external canal closure that was reclosed successfully under local anesthesia. All patients were using the device at the last follow-up interval with no device problems. CONCLUSION: Blind-sac closure of the external ear canal without obliteration is a rather safe surgical procedure in cases with chronic otitis media or atelectasis. Meticulous surgical technique and proper patient selection are of paramount importance. However, a 2-stage procedure may not always be necessary and might best be confined to those patients who have active inflammatory disease at the primary procedure.     

Surgical considerations and safety of cochlear implantation in otitis media with effusion

Objective

To evaluate the effects of otitis media with effusion on surgical parameters, patient safety, perioperative and postoperative complications.

How I do it/short communication: the middle temporal artery flap for coverage of an exposed cochlear implant cable in the mastoid cavity

Abstract

A patient who had previously undergone a modified radical mastoidectomy subsequently underwent cochlear implantation with good results. At surgery the mastoid cavity was partially obliterated to provide soft tissue cover for the implant cables. Following local infection the cable became exposed and we used a middle temporal artery local flap to provide cover for the cable. The anatomy of the flap and methods used are described here. The patient continues to have good hearing from the implant with a good coverage over the cable. Copyright © 2006 John Wiley & Sons, Ltd.     

Intracochlear Perfusion of Pneumolysin,a Pneumococcal Protein,Rapidly Abolishes Auditory Potentials in the Guinea Pig Cochlea

Objective —Bacterial meningitis and chronic suppurative otitis media caused by Streptococcus pneumoniae are associated with considerable otological morbidity. Specifically, sensorineural hearing loss is a permanent sequela in a third of those who contract pneumococcal meningitis. Pneumolysin, a pneumococcal protein, has been implicated as one of the main virulence/cytotoxic factors. Its pathogenicity is intimately dependent on an ability to form transmembrane pores on binding with cholesterol in target tissues.

Material and Methods —We perfused wild-type pneumolysin, at a number of different concentrations, into the guinea pig cochlea and used electrocochleography to characterize the effects of this cytolytic exotoxin in the organ of Corti.

Results —Intracochlear perfusion of pneumolysin (10 μg/50 μl) reduced the compound action potential of the auditory nerve within seconds. The cochlear microphonics (f1=8 kHz, f2=9.68 kHz) and their distortion product (2f1–f2) were also reduced, albeit in a slightly less dramatic fashion. At lower concentrations (1 μg/50 μl), a selective and earlier effect on inner hair cells was observed.

Conclusions —These results clearly show that significant ototoxicity ensues when sensory cells of the organ of Corti are exposed to pneumolysin (and complete cochlear death when the concentration is high enough). Toxicity is dose-dependent and appears to be site-sensitive. This may have implications for any possible future protective strategies against pneumococcal disease in the ear.     

Case report of a child with otoacoustic emissions and profound hearing loss in whom otoacoustic emissions were preserved after cochlear implantation

Abstract

Objective and importance

To highlight the complications of using hydroxyapatite (HA) bone cement when implanting a cochlear implant (CI) device.

Clinical presentation

A case series of three patients who had undergone cochlear implantation are presented. A bony defect was seen in the external auditory meatal wall posteriorly in all three cases. This was intimately related to the site of HA bone cement, which had been used to anchor the electrode array at the time of the original implantation. Persistent otorrhoea was usually a feature at clinical presentation.

Intervention (and technique)

Removal of the HA bone cement and repair of the bony defect has resulted in resolution of the otorrhoea and a functioning CI is present in all cases without further complications.

Conclusion

The use of HA bone cement in cochlear implantation may cause dehiscence of the external auditory meatal wall. Our experience has shown that the electrode array does not need to be secured with cement. It is therefore recommended by this centre that HA cement should not be used to secure the electrode array in cochlear implantation surgery.     

Iatrogenic facial nerve exposure in cochlear implant surgery: incidence and clinical significance in the absence of intra-operative nerve monitoring

Objectives: Iatrogenic facial nerve injury is one of the most feared complications of cochlear implantation. Intraoperative facial nerve monitoring is used as an adjunctive modality in a variety of neurotologic surgeries including cochlear implantation. With the lack of nerve monitoring, there is a theoretically higher risk of iatrogenic fallopian canal dehiscence with facial nerve exposure, particularly the mastoid portion, during cochlear implant surgery. The purpose of this study is to determine the incidence of iatrogenic exposure of the facial nerve and its relation to the incidence of post-operative facial paralysis in the absence of facial nerve monitoring.

Methods: This was a retrospective study. Medical charts of 307 patients who underwent cochlear implantation without facial nerve monitoring, from 2012 to 2017 were reviewed to identify cases with a reported iatrogenic defect over the mastoid facial nerve. The incidence of post-operative facial palsy was determined and compared to the incidence with the use of intra-operative monitoring which has been reported in the literature.

Results: The incidence of iatrogenic dehiscence with facial nerve exposure was 46.58%. However, the incidence of post-operative facial palsy was only 2.1% which decreased to 0.72% in cases without injury of the facial neural sheath. This was not significantly different from the 0.73% rate reported in the literature with the use of intra-operative facial monitoring (P?=?0.99).

Conclusion: The incidence of iatrogenic facial nerve exposure during cochlear implantation may be relatively high. However, no additional risk of post-operative facial nerve paralysis was found, provided that the integrity of the neural sheath was preserved, even with the lack of intra-operative monitoring.     

Impedance changes in chronically implanted and stimulated cochlear implant electrodes

Abstract

Objectives

Electrode impedance increases following implantation and undergoes transitory reduction with onset of electrical stimulation. The studies in this paper measured the changes in access resistance and polarization impedance in vivo before and following electrical stimulation, and recorded the time course of these changes.

Design

Impedance measures recorded in (a) four cats following 6 months of cochlear implant use, and (b) three cochlear implant recipients with 1.5–5 years cochlear implant experience.

Results

Both the experimental and clinical data exhibited a reduction in electrode impedance, 20 and 5% respectively, within 15–30 minutes of stimulation onset. The majority of these changes occurred through reduction in polarization impedance. Cessation of stimulation was followed by an equivalent rise in impedance measures within 6–12 hours.

Conclusions

Stimulus-induced reductions in impedance exhibit a rapid onset and are evident in both chronic in vivo models tested, even several years after implantation. Given the impedance changes were dominated by the polarization component, these findings suggest that the electrical stimulation altered the electrode surface rather than the bulk tissue and fluid in the cochlea.