Facial nerve stimulation associated with cochlear implant use following temporal bone fractures

Hearing Performance in Cochlear Implant Users Who Have Facial Nerve Stimulation

Introduction  Facial nerve stimulation (FNS) is a complication in cochlear implant (CI) when the electrical current escapes from the cochlea to the nearby facial nerve. Different management to reduce its effects are available, although changes might result in a less-than-ideal fitting for the CI user, eventually reducing speech perception. Objective  To verify the etiologies that cause FNS, to identify strategies in managing FNS, and to evaluate speech recognition in patients who present FNS. Methods  Retrospective study approved by the Ethical Board of the Institution. From the files of a CI group, patients who were identified with FNS either during surgery or at any time postoperatively were selected. Data collection included: CI manufacturer, electrode array type, age at implantation, etiology of hearing loss, FNS identification date, number of electrodes that generated FNS, FNS management actions, and speech recognition in quiet and in noise. Results  Data were collected from 7 children and 25 adults. Etiologies that cause FNS were cochlear malformation, head trauma, meningitis, and otosclerosis; the main actions included decrease in the stimulation levels followed by the deactivation of electrodes. Average speech recognition in quiet before FNS was 86% and 80% after in patients who were able to accomplish the test. However, there was great variability, ranging from 0% in quiet to 90% of speech recognition in noise. Conclusion  Etiologies that cause FNS are related to cochlear morphology alterations. Facial nerve stimulation can be solved using speech processor programming parameters; however, it is not possible to predict outcomes, since results depend on other variables.

Auditory rehabilitation after temporal bone fracture with cochlear implants - a case control study

OBJECTIVES

Temporal bone fracture can cause posttraumatic deafness. Sequelae like ossification or obliteration of the cochlea can impact the outcome of cochlear implantation. This study highlights the effect of localisation of the fracture to morphologic, electric and functional criteria.

METHODS

The study group consists of patients suffering from hearing loss caused by temporal bone fracture (n = 61 ears). Patients were divided into otic capsule sparing (OCS) and otic capsule involving (OCI) fractures. The OCI group was additionally divided into subgroups with or without signs of ossification inside the cochlea. Postoperative imaging, hearing tests and electrode impedances were analysed.

RESULTS

The results of postoperative hearing rehabilitation showed lower speech understanding scores for the OCI group, especially for the ossification group. OCI fractures with signs of ossification showed increased impedances. Patients in the OCI group suffered more frequently from facial nerve stimulation (FNS). FNS was most frequently observed within the ossification group.

CONCLUSION

Cochlear implantation in patients with temporal bone fracture is adequate therapy for the treatment of fracture-induced deafness. In long-term observation, these patients show comparable results with regular cochlear implant (CI) patients. Implantation should be performed as soon as possible after hearing loss, before obstructing obliteration or ossification of the cochlea start.

Cochlear re-implantation with the use of multi-mode grounding associated with anodic monophasic pulses to manage abnormal facial nerve stimulation

Objectives: To investigate the outcomes of cochlear re-implantation using multi-mode grounding stimulation associated with anodic monophasic pulses to manage abnormal facial nerve stimulation (AFNS) in cochlear implant (CI) recipients. Methods: Retrospective case report. An adult CI recipient with severe AFNS and decrease in auditory performance was re-implanted with a new CI device to change the pulse shape and stimulation mode. Patient's speech perception scores and AFNS were compared before and after cochlear re-implantation, using monopolar stimulation associated with cathodic biphasic pulses and multi-mode stimulation mode associated to anodic monophasic pulses, respectively. The insertion depth angle and the electrode-nerve distances were also investigated, before and after cochlear re-implantation. Results: AFNS was resolved, and the speech recognition scores rapidly increased in the first year after cochlear re-implantation while remaining stable. After cochlear re-implantation, the e15 and e20 electrodes showed shorter electrode-nerve distances compared to their correspondent e4 and e7 electrodes, which induced AFNS in the first implantation. Conclusions: Cochlear re-implantation with multi-mode grounding stimulation associated with anodic monophasic pulses was an effective strategy for managing AFNS. The patient's speech perception scores rapidly improved and AFNS was not detected four years after cochlear re-implantation.

Postoperative radiological assessment of the mastoid facial canal in cochlear implant patients in correlation with facial nerve stimulation

Objectives

To correlate the radiological assessment of the mastoid facial canal in postoperative cochlear implant (CI) cone-beam CT (CBCT) and other possible contributing clinical or implant-related factors with postoperative facial nerve stimulation (FNS) occurrence.

Methods

Two experienced radiologists evaluated retrospectively 215 postoperative post-CI CBCT examinations. The mastoid facial canal diameter, wall thickness, distance between the electrode cable and mastoid facial canal, and facial-chorda tympani angle were assessed. Additionally, the intracochlear position and the insertion angle and depth of electrodes were evaluated. Clinical data were analyzed for postoperative FNS within 1.5-year follow-up, CI type, onset, and causes for hearing loss such as otosclerosis, meningitis, and history of previous ear surgeries. Postoperative FNS was correlated with the measurements and clinical data using logistic regression.

Results

Within the study population (mean age: 56 ± 18 years), ten patients presented with FNS. The correlations between FNS and facial canal diameter (p = 0.09), wall thickness (p = 0.27), distance to CI cable (p = 0.44), and angle with chorda tympani (p = 0.75) were statistically non-significant. There were statistical significances for previous history of meningitis/encephalitis (p = 0.001), extracochlear-electrode-contacts (p = 0.002), scala-vestibuli position (p = 0.02), younger patients’ age (p = 0.03), lateral-wall-electrode type (p = 0.04), and early/childhood onset hearing loss (p = 0.04). Histories of meningitis/encephalitis and extracochlear-electrode-contacts were included in the first two steps of the multivariate logistic regression.

Conclusion

The mastoid-facial canal radiological assessment and the positional relationship with the CI electrode provide no predictor of postoperative FNS. Histories of meningitis/encephalitis and extracochlear-electrode-contacts are important risk factors.

Key Points

• Post-operative radiological assessment of the mastoid facial canal and the positional relationship with the CI electrode provide no predictor of post-cochlear implant facial nerve stimulation.

• Radiological detection of extracochlear electrode contacts and the previous clinical history of meningitis/encephalitis are two important risk factors for postoperative facial nerve stimulation in cochlear implant patients.

• The presence of scala vestibuli electrode insertion as well as the lateral wall electrode type, the younger patient’s age, and early onset of SNHL can play important role in the prediction of post-cochlear implant facial nerve stimulation.

Performance of cochlear implant recipients fitted with triphasic pulse patterns

PURPOSE

To assess the effect of triphasic pulse pattern stimulation strategy on the audiological performance of cochlear implant recipients with unintended facial nerve stimulation (FNS), and to compare the audiological and speech outcomes before and after switching to triphasic stimulation.

METHODS

A retrospective study of patients who have changed their fitting maps from biphasic to triphasic pulse pattern stimulation because of FNS after cochlear implantation (CI). All identified patients with FNS after CI from 2017 to 2019 were included in this study. The medical records of 11 patients (16 ears) were queried for demographic and radiological data, pure tone audiometry, speech reception thresholds, speech discrimination score at 65 dB, maximum comfortable levels, thresholds, and dynamic range. Then, these parameters were compared in the two conditions, biphasic and triphasic.

RESULTS

Using triphasic pulse stimulation only or combined with switch-off of few channels, complete resolution of FNS was achieved. Triphasic pulse pattern stimulation was associated with better speech discrimination scores (75.25 ± 26.13%) compared to the biphasic pulse (58.25 ± 26.13%). This triphasic strategy also showed higher maximum comfortable levels (36.62 ± 1.63 qu) than biphasic strategy (31.58 ± 2.5 qu). Moreover, the dynamic range was wider using triphasic pulse strategy. In general, the triphasic pulse pattern resulted in successful suppression of facial nerve stimulation with suitable maximum comfortable levels and better speech discrimination.

CONCLUSION

Triphasic pulse pattern stimulation is an appropriate tool in controlling FNS following cochlear implantation with wider dynamic range. We recommend that all patients with facial nerve stimulation after CI surgery be switched to a triphasic pulse program prior to considering further surgery.

Long-term cochlear implantation outcomes in patients following head injury

OBJECTIVE

In cases of a severe to profound sensorineural hearing loss following head injury, the cochlear implant (CI) is the primary option for auditory rehabilitation. Few studies, however, have investigated long-term CI outcomes in patients following head trauma, including those without temporal bone fracture (TBF). Herein, the aim of this study is to examine CI outcomes following cases of head injury with and without TBF.

METHODS

Audiometric outcomes of patients who received a CI due to a head injury resulting in severe to profound hearing loss at two tertiary care hospitals were analyzed. Patients were divided into those who received a CI in a fractured temporal bone (group A, n = 11 patients corresponding to 15 ears) and those who received a CI in a non-fractured temporal bone (group B, n = 8 patients corresponding to nine ears). Primary outcomes included duration of deafness prior to CI and postoperative consonant-nucleus-constant whole word (CNC) scores.

RESULTS

Nineteen patients (84% male), corresponding to 24 CIs, were identified. Fifteen CI were performed on ears with TBF (group A), and nine CI were performed on ears without TBF (group B). No patients had an enlarged vestibular aqueduct (EVA). The mean duration of deafness was 5.7 and 11.3 years in group A and group B, respectively. The mean duration of CI follow-up (CI experience) was 6.5 years in group A and 2.1 years in group B. The overall mean postoperative CNC score for all subjects was 68.6% (±21.2%, n = 19 with CNC testing). There was no difference in CNC score between group A and group B (69.8% and 66% respectively, P = .639).

CONCLUSION

The study is among the largest series examining long-term outcomes of CI after head injury. CI is an effective method for auditory rehabilitation in patients after head injury.

LEVEL OF EVIDENCE

IV.

Investigating Facial Nerve Stimulation After Cochlear Implantation in Adult and Pediatric Recipients

OBJECTIVES/HYPOTHESIS

Facial nerve stimulation (FNS) can occur after cochlear implantation for a small number of recipients. This study aimed to investigate if a correlation exists between the variables involved in FNS.

STUDY DESIGN

Retrospective cohort review.

METHODS

There were 32 out of 1,100 cochlear implant recipients who experienced FNS in our clinic between 2010 and 2019. The following variables were recorded from a retrospective chart review: grade of FNS, onset of FNS, the number of channels stimulating FNS, and radiological findings of abnormalities in the inner ear. Statistical analyses were performed to identify a correlation between any of the variables involved. The techniques used to reduce FNS were analyzed.

RESULTS

Eleven adult ears had progressive hearing loss, three had idiopathic sudden sensorineural hearing loss (SNHL), and one congenital SNHL. All pediatric ears were diagnosed with congenital SNHL, except for one ear with idiopathic sudden SNHL. The grade of FNS ranged from mild stimulation or slight motion in the eye, mouth, nasolabial, or forehead regions (n = 8) to total severe stimulation of the facial musculature and/or severe pain (n = 3). The onset of FNS occurred immediately after activation for nine ears, and up to 16 months later for the other subjects. A significant correlation was observed between the number of channels stimulating FNS, the grade of FNS, and the radiological findings of the inner ear. FNS was completely resolved for 30 ears and partially resolved for two ears.

CONCLUSIONS

FNS can occur any time after cochlear implantation and can affect both adult and pediatric. However, it can be effectively resolved using specific fitting techniques.

LEVEL OF EVIDENCE

2c Laryngoscope, 131:374-379, 2021.

Comparison of Temporal Bone Parameters before Cochlear Implantation in Patients with and without Facial Nerve Stimulation

Background and Objectives

Facial nerve stimulation (FNS) is a complication of cochlear implantation (CI). This study compared the thickness and density of the bone separating the upper basal turn of the cochlea (UBTC) and the labyrinthine segment of the facial nerve (LSFN) on preoperative computed tomography (CT) in patients with and without FNS after CI.

Subjects and Methods

Adult patients who underwent CI from January 2011 to February 2017 with preoperative CT at a tertiary referral hospital were considered for this retrospective case–control study. Patients were divided into two groups: with FNS (n=4) and without FNS (n=53). The density and thickness of the bone between the LSFN and UBTC were measured on preoperative CT. Charts were reviewed for other parameters.

Results

A statistically significant difference was seen in the thickness (p=0.007) but not in the density (p=0.125) of the bone between the UBTC and LSFN. Four patients had FNS at the mid-range electrode arrays, and one of them additionally had FNS at the basal arrays.

Conclusions

Decreased thickness of the bone between the UBTC and LSFN can explain postoperative FNS, confirming the histologic and radiologic findings in previous studies, which indicated that the thickness of the temporal bone between the LSFN and UBTC is less in patients who experience FNS. While the density in this region was also less, it was not statistically significant.

Anatomical Characteristics of Facial Nerve and Cochlea Interaction

Objective: The aim was to study the relationship between the labyrinthine portion (LP) of the facial canal and the cochlea in human inner ear molds and temporal bones using micro-CT and 3D rendering. A reduced cochlea-facial distance may spread electric currents from the cochlear implant to the LP and cause facial nerve stimulation. Influencing factors may be the topographic anatomy and otic capsule properties. Methods: An archival collection of human temporal bones underwent micro-CT and 3D reconstruction. In addition, cochlea-facial distance was assessed in silicone and polyester resin molds, and the association between the LP and upper basal turn of the cochlea was analyzed. Results: Local thinning of the otic capsule and local anatomy may explain the development of cochlea-facial dehiscence, which was found in 1.4%. A reduced cochlea-facial distance was noted in 1 bone with a superior semicircular canal dehiscence but not in bones with superior semicircular canal “blue line.” The otic capsule often impinged upon the LP and caused narrowing. Conclusion: Micro-CT with 3D rendering offers new possibilities to study the topographic anatomy of the human temporal bone. The varied shape of the cross-section of the LP could often be explained by an “intruding” cochlea.