Postural control before and after cochlear implantation: standard cochleostomy versus round window approach

Various approaches to the round window for cochlear implantation: a systematic review

OBJECTIVE

Round window approaches are used to insert a cochlear implant electrode array into the scala tympani. This study aimed to review the literature to find the reported round window approaches.

METHOD

This review was performed according to the Preferred Reporting Items for Systematic Review and Meta-Analyses ('PRISMA') guidelines. Articles that described their surgical approach to the round window were included. The PubMed, Scopus, Web of Science and Cochrane Library electronic databases were searched through to June 2021. The study protocol was registered on Prospero (reference number: CRD42021226940).

RESULTS

A total of 42 reports were included. The following approaches were documented: the standard facial recess, keyhole, retrofacial, modified suprameatal, transaditus, combined posterior tympanotomy and endomeatal, modified Veria, canal wall down approaches, and endoscopically assisted technique.

CONCLUSION

This review suggested that there are numerous distinct round window approaches, providing alternatives when the round window is inaccessible through the standard facial recess.

Relative efficacy of veria and mastoidectomy techniques of cochlear implantation in preservation of sound-induced saccular responses

OBJECTIVE

Cochlear implantation (CI) is a safe technique to give hearing sensation to a person with hearing impairment. The present study aimed to compare the two surgical approaches of CI, mastoidectomy and veria, for their effects on saccular function assessed using cervical vestibular-evoked myogenic potential (cVEMP).

DESIGN

Multiple group time series design.

STUDY SAMPLE

The study included 63 children (3-8 years old) who underwent CI using veria technique (n = 20) and mastoidectomy approach (n = 43). The 500-Hz tone-burst evoked cVEMP were recorded on three occasions- a day before CI surgery, a day after the device switch-on and 4 months after the switch-on.

RESULTS

The post-implant results revealed the absence of cVEMP in nearly 40% of the participants. The amplitudes were significantly lower at the time of the switch-on and at the 4-months follow-up period (p < 0.05). Among the participants undergoing CI using mastoidectomy approach, amplitudes were significantly larger after surgery than those undergoing surgery using veria technique (p < 0.05).

CONCLUSIONS

The saccular responses are better preserved with the mastoidectomy technique than the veria technique for CI surgery.

Does cochlear implantation influence postural stability in patients with hearing loss?

BACKGROUND

Cochlear implantation (CI) procedure carries the potential risk for vestibular system insult or stimulation with resultant dysfunction due to its proximity to the cochlea. The vestibular system plays an essential role in crucial tasks such as postural control, gaze stabilization and spatial orientation.

RESEARCH QUESTION

How does standard cochlear implantation influence postural stability in patients with hearing loss?

METHODS

The study included 21 individuals (age 51 ± 18 years) qualified to undergo CI due to severe or profound hearing loss. Participants were qualified for both groups by a physician based on an interview, an otoneurological examination and vestibular tests. The first group included patients without vestibular dysfunction, whereas the other group consisted of persons with vestibular dysfunction. The research methodology included medical examinations, anthropometric measurements and stabilometry on the Biodex Balance System SD (BBS) platform. The examinations were carried out twice, i.e. prior to and 3 months post implantation. The recorded data was compared between the first and the second examination using a non-parametric Wilcoxon test. The analysis of variance (ANOVA) and Tukey's post-hoc HSD unequal sample sizes were performed for patients with and without vestibular dysfunction.

RESULTS AND SIGNIFICANCE

Study showed that 52.4% of the participants obtained results within the norm, while 47.6% scored below it. The comparison of stability indices of the examined individuals, with and without vestibular dysfunction, did not reveal statistically significant differences. The only difference was the anterior-posterior stability index assessed in static conditions. Three months after the implantation, no changes in the majority of indices were noted, with the exception of anterior-posterior stability index, which improved following the implantation. CI does not affect postural stability changes in the study participants.

Vestibular Outcome After Cochlear Implantation Is Not Related to Surgical Technique: A Double Blinded, Randomized Clinical Trial of Round Window Approach Versus Cochleostomy

To establish whether the round window approach (RWA) leads to less vestibular dysfunction and dizziness than the standard cochleostomy approach (SCA) during cochlear implant (CI) surgery, as assessed using the video head impulse test (vHIT).

Additionally, objective findings were compared with the subjective dizziness perceived by the patient.

Cochlear Implant Surgery and the Risk of Falls in an Adult Population

OBJECTIVE

To determine the effect of cochlear implant surgery on the balance and risk of falls in an adult patient population using a mobile posturograph.

DESIGN

Prospective clinical pilot study.

SETTING

Cochlear implant center at a tertiary referral hospital.

SUBJECTS AND METHODS

Twenty adult patients undergoing cochlear implant surgery were tested using a mobile posturograph (VertiGuard). The standard balancing deficit test, or the geriatric standard balancing deficit test protocol (for patients older than 60 yr), was performed both 1 day before and 3 to 5 days after surgery.

OUTCOME MEASURES

The risk of falls (%) was calculated from the body sway both forward-to-backward and side-to-side in degrees per second.

RESULTS

The mean preoperative risk of falls in the whole study population was 51% (24-max. 86%) and was thus already higher than that in a normal healthy population (norm 0-40%). Comparison of the postoperative risk of falls to the preoperative risk for all 20 patients revealed a mean increased risk of falls of 1.25% after CI surgery. This is not a statistically significant increase. There was also no statistically significant increase when comparing the fall risk calculated using either the standard balancing deficit test protocol or the geriatric standard balancing deficit test protocol alone.

CONCLUSION

Postural control in cochlear implant candidates is already decreased before surgery compared with a healthy population. However Comparison of pre- and postoperative body sway measurements did not reveal a significant increase in fall risk as a result of cochlea implant surgery. Therefore in this study population, cochlear implant surgery did not influence balance and risk of falls. Further testing with a larger study population would be necessary to determine the development of falls risk over time after cochlear implant surgery.

Assessing Gait Stability before and after Cochlear Implantation

Background

It is known that cochlear implantation may alter the inner ear and induce vestibular disorders.

Research Question

How does cochlear implantation influence gait stability? Material and Methods. An experimental group of twenty-one subjects scheduled for cochlear implantation underwent gait testing twice, on the day before cochlear implantation (BCI) and three months after cochlear implantation (ACI), using a motion capture system. A control group of 30 age-matched healthy individuals were also tested.

Results

In the experimental group, the gait stability ratio (GSR) was found to improve in 17 subjects after implantation, by an average of 6%. Certain other parameters also showed statistically significant improvement between the two experimental group tests: step time (p<0.001), single-support phase walking speed (p<0.05), and center of mass (CoM) (p<0.05). Using the CoM results of the control group, we devised a stability classification system and applied it to the pre- and postimplantation subjects. After implantation, increases were seen in the number of subjects classified in interval II (strong stability) and III (weak stability). The number of subjects in interval I (perfect stability) decreased by 1 and in interval IV (no stability) by 4.

Significance

(1) Although cochlear implantation intervenes in the vestibular area, we found evidence that gait stability improves in most subjects after the surgery, reducing the risk of falls. (2) We found statistically significant improvements in individual parameters (such as single-support phase time), in GSR, and in CoM. (3) Based on CoM results, we proposed a new rule-of-thumb way of classifying patients into gait stability intervals, for use in rehabilitation planning and monitoring.

Cochlear implantation using the underwater technique: long-term results

INTRODUCTION

The opening of the round window and the insertion of the electrode array into the scala tympani during cochlear implant surgery can lead to a pressure shock of the delicate inner ear structures. By filling the tympanic cavity with Ringer Solution during these surgical steps (underwater technique), the hydrostatic pressure of the fluid acts as a smooth pressure stabilizer, avoiding a pressure shock of the inner ear structures. The aim of this retrospective study was to present long-term results of this new method of cochlear implantation in underwater technique.

METHODS

Altogether, 47 implantations in 43 patients with residual hearing at the frequencies 250, 500 and 1000 Hz in the unaided preoperative pure tone audiometry were included. A cochlear implantation via round window with a conventional full-length electrode was performed in underwater technique. Changes of residual hearing 7 weeks and 24 months after surgery were analyzed.

RESULTS

Overall postimplant hearing preservation 7 weeks after implantation was achieved in 22 ears (47%). Subsequent follow-up was performed on average 24 months after surgery (range 12 months-4.2 years) in all patients. At this late postoperative evaluation, preservation of hearing was recorded in 18 ears (38%). Neither the follow-up time nor the type of electrode had a significant impact on the postoperative hearing loss.

CONCLUSION

The underwater technique is an atraumatic cochlear implantation technique with hearing preservation rates comparable to results in literature and a very small hearing preservation decline rate over time even when using full-length CI electrodes.

Vestibular dysfunction and postural balance in cochlear implant users: a narrative literature review

ABSTRACT Cochlear implants directly stimulate nerve fibers and ganglion cells of the auditory nerve, which transform sound energy into low levels of electrical current, stimulating the remaining fibers of the auditory nerve in patients with severe to profound hearing loss, in order to provide the significant range of auditory sensation and speech comprehension. Due to the close relationship between cochlea and vestibular receptors, some patients may present vestibular and postural balance changes concomitantly after surgery. This study aimed to perform a narrative review of the main studies that relate vestibular symptoms in patients implanted in the last six years. The research was performed through the databases: SciELO, LILACS and PubMed, using associated descriptors for "cochlear implant", "vestibular dysfunction", "vertigo" and "balance", totalizing 21 studies that fitted the inclusion criteria. The results were described in a chronological order of publication, showing the main conclusions. Of the total studies analyzed, 18 related vestibular function to cochlear implant and only 3 studies did not find such a relationship. The literature characterize the effects of the cochlear implant on the vestibular system, however, the results are contradictory.

Meta-analysis of subjective complaints of vertigo and vestibular tests after cochlear implantation

OBJECTIVE

Postoperative vertigo is a common complaint after cochlear implantation, but published incidence rates differ vastly. The aim of the present study was to investigate both subjective complaints of vertigo before and after cochlear implantation and related vestibular diagnostic tests on cochlear implant candidates.

DATA SOURCES

We performed a systematic literature search according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement in PubMed, Cochrane Register, and EMBASE.

REVIEW METHODS

We presented 116 eligible studies investigating subjective complaints of vertigo after cochlear implantation and/or related vestibular diagnostic tests. We conducted three meta-analyses of 46 eligible studies with matched pre- and postoperative data to calculate the odds ratio of new vertigo onset, as well as the impairment of vestibular receptors measured by nystagmography and cervical vestibular evoked myogenic potentials (cVEMP). Postoperative vertigo was calculated from 95 studies and further subdivided by mean age with pooled data.

RESULTS

We observed a significant increase in postoperative vertigo and significant impairment of nystagmography and cVEMP detection. Vertigo after cochlear implantation was reported in 9.3% of the patients with a continuous increase in patient age at surgery. In a subgroup of studies, new onset of vertigo was found in 17.4% of the patients. In addition, 7.2% of the patients had persisting vertigo complaints, whereas 11.6% described an altered vertigo quality and 7.7% had their preoperative complaints resolved. A comparison of round window approach and cochleostomy revealed significantly increased vertigo after cochleostomy. Both insertion methods showed similar effects in nystagmography and cVEMP testing.

CONCLUSION

Cochlear implantation has a significant impact on subjective vertigo and vestibular receptor function. This is affected by the patient's age at the time of surgery. The surgical technique (round window or cochleostomy) may influence the outcome, but this requires further investigation. Younger patients may compensate better following vestibular dysfunction. Perioperative testing is required to correlate vestibular impairment and subjective complaints. Laryngoscope, 2018 Laryngoscope, 128:2110-2123, 2018.

Effect of cochlear implant surgery on vestibular function: meta-analysis study

Importance

Vestibular disorders have been reported following cochlear implant (CI) surgery, but the literature shows a wide discrepancy in the reported clinical impact. The aim of this meta-analysis is to quantify the effect of CI before and after surgery on the outcomes of vestibular tests, postural stability, and subjective perception of dizziness.

Objective

To evaluate the effects of CI surgery on vestibular function in adult patients (≥18 years) with sensorineural hearing loss who underwent unilateral or bilateral implantation.

Data sources

MEDLINE, PubMed, Web of Science and Cochrane Library from January 1, 1995, through July 12, 2016.

Study selection

Published studies of adult patients who received unilateral or bilateral CIs and whose vestibular function or postural stability was assessed before and after surgery.

Data extraction

From each study, test results before and after surgery were compared, for the following five tests: clinical head impulse test (HIT); bi-thermal caloric irrigation of the horizontal semicircular canal; vestibular evoked myogenic potential (VEMP); dizziness handicap inventory (DHI); and computerized dynamic posturography (CDP).

Results

Twenty-seven studies met all inclusion criteria. Most studies performed either bi-thermal caloric irrigation and/or VEMP, with fewer studies investigating changes in HIT, posturography or DHI. CI surgery significantly affected the results of caloric and VEMP testing. However, HIT results, posturography, and DHI, scores were not significantly affected after CI surgery.

Conclusions and relevance

CI surgery has a significant negative effect on the results of caloric as well as VEMP tests. No significant effect of CI surgery was detected in HIT, posturography, or DHI scores. Overall, the clinical effect of CI surgery on the vestibular function was found to be insignificant. Nonetheless, the potential effects of surgery on the vestibular system should be discussed with CI candidates before surgery.

Impairment of Caloric Function After Cochlear Implantation

PURPOSE

This article seeks to review current literature on caloric function following cochlear implantation while analyzing any correlations of caloric function changes with vestibular symptoms.

METHOD

This article is a systematic review of evidence-based literature. English language articles published between 1980 and 2014 that presented some form of caloric data from cochlear implant (CI) patients and that did not solely analyze overlapping data from a previous study were reviewed. Twenty-five articles met these criteria.

RESULTS

Of the 439 individuals tested, 37% of patients demonstrated reduced maximum slow-phase velocity, and 34% had onset of caloric asymmetry post-CI.

CONCLUSIONS

This review article found that cochlear implantation can affect caloric responses but is variable. When counseling patients preoperatively, possible effects of CI on labyrinthine function should be discussed.

Short-term risk of falling after cochlear implantation

Cochlear implantation is a highly effective intervention for hearing loss, but insertion of an implant into the cochlea is often accompanied by loss of residual hearing function. Sometimes, postoperative testing also shows loss of function in the semicircular canals or otolith organs. The effect of this loss on equilibrium, particularly in the short term following surgery, and the risk of falling due to this loss is unknown. We prospectively measured balance in 16 consecutive adult cochlear implant patients before and 2 weeks after surgery. Subjects stood on a foam pad with eyes closed, feet together and arms at the side. The length of time over which this posture could be maintained was recorded up to a maximum value of 30 s indicating normal performance. Ten of 16 subjects reached a maximal time on preoperative testing. Nine of 16 subjects lost balance function after surgery. Four of the 10 subjects with normal preoperative balance function lost function. Subjects older than the age of 60 were more likely to lose balance function than younger subjects. We used previously published values relating balance performance on foam to risk of falling to calculate the fall risk among our subjects. The relative risk of falling increased after surgery by more than threefold in some patients. Imbalance after cochlear implantation may be much more common, particularly in the short term, than previously appreciated. This imbalance is accompanied by an increased risk of falling in many patients. Careful preoperative counseling before implantation and postoperative therapeutic intervention to improve comfort and reduce the chance of falling may be warranted, particularly in patients at a risk for injuries from falls (level of evidence: 2b).

Static and dynamic posture control in postlingual cochlear implanted patients: effects of dual-tasking, visual and auditory inputs suppression

Posture control is based on central integration of multisensory inputs, and on internal representation of body orientation in space. This multisensory feedback regulates posture control and continuously updates the internal model of body's position which in turn forwards motor commands adapted to the environmental context and constraints. The peripheral localization of the vestibular system, close to the cochlea, makes vestibular damage possible following cochlear implant (CI) surgery. Impaired vestibular function in CI patients, if any, may have a strong impact on posture stability. The simple postural task of quiet standing is generally paired with cognitive activity in most day life conditions, leading therefore to competition for attentional resources in dual-tasking, and increased risk of fall particularly in patients with impaired vestibular function. This study was aimed at evaluating the effects of postlingual cochlear implantation on posture control in adult deaf patients. Possible impairment of vestibular function was assessed by comparing the postural performance of patients to that of age-matched healthy subjects during a simple postural task performed in static (stable platform) and dynamic (platform in translation) conditions, and during dual-tasking with a visual or auditory memory task. Postural tests were done in eyes open (EO) and eyes closed (EC) conditions, with the CI activated (ON) or not (OFF). Results showed that the postural performance of the CI patients strongly differed from the controls, mainly in the EC condition. The CI patients showed significantly reduced limits of stability and increased postural instability in static conditions. In dynamic conditions, they spent considerably more energy to maintain equilibrium, and their head was stabilized neither in space nor on trunk: they behaved dynamically without vision like an inverted pendulum while the controls showed a whole body rigidification strategy. Hearing (prosthesis on) as well as dual-tasking did not really improve the dynamic postural performance of the CI patients. We conclude that CI patients become strongly visual dependent mainly in challenging postural conditions, a result they have to be awarded of particularly when getting older.

Evaluation of uncompensated unilateral vestibulopathy using the modified clinical test for sensory interaction and balance

OBJECTIVE

To compare the results of the Modified Clinical Test for Sensory Interaction and Balance (mCTSIB) and the Sensory Organization Test (SOT) of computerized dynamic posturography (CDP) to better understand the role and limitations of the mCTSIB in the diagnosis and rehabilitation of patients with uncompensated unilateral vestibulopathy.

STUDY DESIGN

Prospective blind study.

SETTING

Tertiary referral center.

INTERVENTIONS

Ninety-eight patients with uncompensated unilateral vestibulopathy were enrolled. After diagnosis was established through ocular motor studies, head roll and Dix-Hallpike tests, caloric testing, and pure tone audiometry, the mCTSIB and SOT were administered simultaneously.

MAIN OUTCOME MEASURE

Composite or comprehensive scores and equilibrium scores.

RESULTS

When composite or comprehensive scores were used to classify subjects as normal or abnormal, the mCTSIB and SOT showed significant agreement (p > 0.256). SOT condition 2 (eyes closed on a firm surface) showed a greater degree of correlation than did other conditions; the foam-surface or eyes-open conditions yielded poor correlation coefficients.

CONCLUSION

The mCTSIB can be used instead of the SOT in screening to distinguish normality from abnormality in dizzy patients with unilateral vestibulopathy. However, the degree of dizziness assessed by SOT condition was poorly correlated with mCTSIB results, especially in conditions with the eyes open and those using a foam surface.