Cochlear implantation versus auditory brainstem implantation in bilateral total deafness after head trauma: personal experience and review of the literature

Characterization and closed-loop control of infrared thalamocortical stimulation produces spatially constrained single-unit responses

Deep brain stimulation (DBS) is a powerful tool for the treatment of circuitopathy-related neurological and psychiatric diseases and disorders such as Parkinson's disease and obsessive-compulsive disorder, as well as a critical research tool for perturbing neural circuits and exploring neuroprostheses. Electrically mediated DBS, however, is limited by the spread of stimulus currents into tissue unrelated to disease course and treatment, potentially causing undesirable patient side effects. In this work, we utilize infrared neural stimulation (INS), an optical neuromodulation technique that uses near to midinfrared light to drive graded excitatory and inhibitory responses in nerves and neurons, to facilitate an optical and spatially constrained DBS paradigm. INS has been shown to provide spatially constrained responses in cortical neurons and, unlike other optical techniques, does not require genetic modification of the neural target. We show that INS produces graded, biophysically relevant single-unit responses with robust information transfer in rat thalamocortical circuits. Importantly, we show that cortical spread of activation from thalamic INS produces more spatially constrained response profiles than conventional electrical stimulation. Owing to observed spatial precision of INS, we used deep reinforcement learning (RL) for closed-loop control of thalamocortical circuits, creating real-time representations of stimulus-response dynamics while driving cortical neurons to precise firing patterns. Our data suggest that INS can serve as a targeted and dynamic stimulation paradigm for both open and closed-loop DBS.

Temporal Bone Trauma

Temporal bone trauma represents a potentially underrecognized condition during head injuries and remains an important consideration during the evaluation of these patients. The temporal bone contains many critical neurovascular structures in addition to the primary organs of the auditory and vestibular systems that may be violated during these injuries. Despite the lack of consensus guidelines on the management of these injuries, this review highlights the current literature regarding the diagnosis and management of temporal bone trauma and its potential complications.

Spatially specific, closed-loop infrared thalamocortical deep brain stimulation

Deep brain stimulation (DBS) is a powerful tool for the treatment of circuitopathy-related neurological and psychiatric diseases and disorders such as Parkinson's disease and obsessive-compulsive disorder, as well as a critical research tool for perturbing neural circuits and exploring neuroprostheses. Electrically-mediated DBS, however, is limited by the spread of stimulus currents into tissue unrelated to disease course and treatment, potentially causing undesirable patient side effects. In this work, we utilize infrared neural stimulation (INS), an optical neuromodulation technique that uses near to mid-infrared light to drive graded excitatory and inhibitory responses in nerves and neurons, to facilitate an optical and spatially constrained DBS paradigm. INS has been shown to provide spatially constrained responses in cortical neurons and, unlike other optical techniques, does not require genetic modification of the neural target. We show that INS produces graded, biophysically relevant single-unit responses with robust information transfer in thalamocortical circuits. Importantly, we show that cortical spread of activation from thalamic INS produces more spatially constrained response profiles than conventional electrical stimulation. Owing to observed spatial precision of INS, we used deep reinforcement learning for closed-loop control of thalamocortical circuits, creating real-time representations of stimulus-response dynamics while driving cortical neurons to precise firing patterns. Our data suggest that INS can serve as a targeted and dynamic stimulation paradigm for both open and closed-loop DBS.

Intra-operative identification of a temporal bone fracture line during cochlear implant surgery: a case report

BACKGROUND

Temporal bone fractures are divided into otic capsule sparing and otic capsule involving fractures. In the latter, hearing loss, facial nerve paralysis, cerebrospinal fluid leak and meningitis have been reported to occur. The impact of hearing loss can be devastating, especially when occurring in children, with significant risk to speech development and sound localization. In the event of hearing loss, early rehabilitation is therefore of paramount importance. Identification of an intra-operative fracture line with available images and the outcome of such cases has not been reported.

CASE PRESENTATION

We present the case of a 31-month-old male with an otic capsule involving temporal bone fracture, who presented with ipsilateral profound hearing loss. After all required work-up had been performed, he was admitted for a cochlear implant insertion. Per- operatively, a clear fracture line was seen at the round window niche, but a normal insertion was performed despite the anticipated potential ossification at the fracture line. The dreaded complications of cerebrospinal fluid otorrhea or non-auditory stimulation post-implant did not occur. The peculiarity of this case was its rarity, which was demonstrated by clear images that showed the fracture line on preoperative imaging and intraoperatively.

CONCLUSION

Cochlear implantation in the presence of a visible fracture line is feasible and the surgical procedure must not be aborted at its discovery. In these cases, post-operative bacterial meningitis can occur and should be treated aggressively with systemic antibiotics to avoid contralateral ossification of the labyrinth due to labyrinthitis.

Ten-year follow-up of auditory brainstem implants: From intra-operative electrical auditory brainstem responses to perceptual results

The auditory brainstem implant (ABI) can provide hearing sensation to individuals where the auditory nerve is damaged. However, patient outcomes with the ABI are typically much poorer than those for cochlear implant recipients. A major limitation to ABI outcomes is the number of implanted electrodes that can produce auditory responses to electric stimulation. One of the greatest challenges in ABI surgery is the intraoperative positioning of the electrode paddle, which must fit snugly within the cochlear nucleus complex. While there presently is no optimal procedure for intraoperative electrode positioning, intraoperative assessments may provide useful information regarding viable electrodes that may be included in patients' clinical speech processors. Currently, there is limited knowledge regarding the relationship between intraoperative data and post-operative outcomes. Furthermore, the relationship between initial ABI stimulation with and long-term perceptual outcomes is unknown. In this retrospective study, we reviewed intraoperative electrophysiological data from 24 ABI patients (16 adults and 8 children) obtained with two stimulation approaches that differed in terms of neural recruitment. The interoperative electrophysiological recordings were used to estimate the number of viable electrodes and were compared to the number of activated electrodes at initial clinical fitting. Regardless of the stimulation approach, the intraoperative estimate of viable electrodes greatly overestimated the number of active electrodes in the clinical map. The number of active electrodes was associated with long-term perceptual outcomes. Among patients with 10-year follow-up, at least 11/21 active electrodes were needed to support good word detection and closed-set recognition and 14/21 electrodes to support good open-set word and sentence recognition. Perceptual outcomes were better for children than for adults, despite a lower number of active electrodes.

Bilateral Cochlear Implantations in Temporal Bone Fracture: A Viable Treatment Option

OBJECTIVES/HYPOTHESIS

Although it is surgically more challenging, patients with bilateral temporal bone fractures (TBFs) are potential candidates for successful bilateral cochlear implantation (CI). This study aimed to investigate the feasibility of bilateral implantation in patients with sustained bilateral TBFs.

STUDY DESIGN

Retrospective database study.

METHODS

Seven patients with bilateral cochlear implants who were diagnosed with TBFs were included in this study. Preoperative radiological and audiological evaluations were performed. The outcomes of the CI were also investigated.

RESULTS

Hearing levels were restored to the mild-moderate range (<40 dB) for nearly all patients and they reported an improved quality of life.

CONCLUSIONS

CI in patients with TBF is safe and offers a solution for the restoration of hearing in a population who may experience sudden bilateral deafness. However, preoperative confirmation of intact auditory nerves and patent cochlea is essential to maximize the success of CI in this population.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

A Systematic Review of Cochlear Implantation in Temporal Bone Fractures and the Significance of Otic Capsule Involvement

OBJECTIVE

Head trauma can cause deafness in cases with and without a skull base fracture. Anatomic disruption can occur with skull base fractures, but inner ear structures can also be damaged by the concussive forces of the trauma even without fracture. It is thought that negative prognostic indicators for successful cochlear implantation (CI) for hearing rehabilitation include fractures involving the otic capsule or ossification of the cochlea. This review evaluates success of CI in posttrauma patients.

DATA SOURCES

PubMed/MEDLINE, Cochrane, and Embase.

STUDY SELECTION

Search terms used were "cochlear implant" AND ("trauma" OR "fracture"). Studies including preoperative computed tomography or magnetic resonance imaging and patient-level outcome data were included.

DATA EXTRACTION

Study design, perioperative and postoperative outcomes, and complications were reported. Success rates of CI were compared using χ analysis.

DATA SYNTHESIS

Twenty-three studies encompassing 88 patients who experienced posttraumatic deafness and received subsequent CI were included. CI was reported as successful for 28 of 34 patients (82%) with otic capsule-involving fracture, as compared with 17 of 22 (77%) in those who had an otic capsule-sparing temporal bone fracture, and 15 of 17 (88%) of patients without evidence of fracture (i.e., concussive inner ear injury).

CONCLUSIONS

In patients with posttraumatic hearing loss, success rates do not significantly differ between cases that do or do not involve fractures of the otic capsule. CI for posttraumatic hearing loss is generally successful.

Cochlear implantation after traumatic brain injury without otic capsule fracture: A case report and literature review

OBJECTIVE

The aim of this study was to report a case of cochlear implantation (CI) for a patient with an otic capsule-sparing traumatic brain injury (TBI) and to review the relevant literature.

METHODS

A patient with history of TBI received a CI for bilateral profound hearing loss. A systematic review of the literature was performed to identify and compare similar cases.

RESULTS

A 36-year-old male with a history of hearing loss from right acute labyrinthitis was referred for bilateral profound sensorineural hearing loss (SNHL) after a fall with associated injury to the central auditory nervous system (CANS) including the brainstem. On the right, behavioral acoustic threshold measurements were in the profound range with absent OAEs. On the left, testing revealed no measurable behavioral acoustic thresholds and variable physiologic measures. A right unilateral cochlear implant was performed with most recent follow-up demonstrating speech awareness thresholds of 25 dB HL with excellent detection of all 6 Ling sounds. However, the patient also continues to suffer from other neurologic sequelae related to his TBI, which challenge his ability to demonstrate objective and subjective benefit. A systematic review of the literature demonstrates variable outcomes for patients with TBI and SNHL.

CONCLUSIONS

Patients with profound SNHL and TBI present a distinct rehabilitative challenge for clinicians. CI may provide meaningful benefit in this population, though care should be taken in patient selection and counseling.

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.

Evaluation of Subtotal Petrosectomy Technique in Difficult Cases of Cochlear Implantation

OBJECTIVES

To assess the validity of the subtotal petrosectomy (STP) technique in problematic cases of cochlear implant (CI) surgery, and review indications, outcomes, and related controversies.

STUDY DESIGN

This is a retrospective review of data from a private quaternary referral center of otology and skull base surgery.

PATIENTS AND METHODS

A review of patients who underwent CI with STP (STP-CI) as the leading approach was performed. Demographics, indications, surgical details, and main outcomes were evaluated. The surgeries performed were usually single-stage procedures encompassing a comprehensive mastoidectomy, blind sac closure of the external auditory canal (EAC), and mastoid obliteration with autologous fat.

RESULTS

A total of 107 cases were included. Mean follow-up was 7.1 years (range 1-13 years). The most frequent indication for STP-CI was chronic otitis media with/without cholesteatoma (32.7%), followed by open mastoid cavity (26.1%), and cochlear ossification (17.7%). Other difficult conditions where STP facilitates successful implantation include inner-ear malformations, temporal-bone trauma, unfavorable anatomic conditions, and revision surgery. A planned staged procedure was performed in 3 cases. The rate of major complications was 5.6% (n = 6). Three patients developed postauricular wound dehiscence which eventually resulted in device extrusion. No cases of recurrent/entrapped cholesteatoma, EAC breakdown, or meningitis were encountered. This is the largest single-center series of STP-CI reported in the literature.

CONCLUSIONS

When CI is intended in technically challenging cases or associated with a high risk of complications, STP is effective and reliable. Safe implantation and excellent long-term outcomes can be achieved provided surgical steps are properly followed. Single-stage procedures can be performed in most cases, even when there is active middle-ear disease.

Hearing Restoration with Cochlear Implantation in Patients Deafened after Blunt Head Trauma

OBJECTIVES

The objective of the study was to assess the outcomes of cochlear implantation in patients deafened following blunt head trauma.

MATERIAL AND METHODS

Retrospective case series review of seven patients post-lingually deafened following blunt head trauma and aided with cochlear implants. The following data were analyzed: Cause of injury, computed tomography results, surgical information, intra- and post-implantation complications, audiometric and speech perception assessment, processor mapping, and data from follow-up appointments.

RESULTS

The median age of patients at the time of cochlear implantation was 29 years. The median time elapsed between head trauma and cochlear implantation was 5.77 months (minimum 0.8 and maximum 6.73 months). The median post-implantation follow-up time was 11.97 years. No facial nerve stimulation was observed in any case. All patients significantly improved their audiology and speech perception performances within a short time following cochlear implantation and CI performance did not decrease with long-term follow-up in any case.

CONCLUSION

The results of this study showed that cochlear implantation is an effective treatment method for patients deafened following blunt head trauma.

Cochlear obliteration following a translabyrinthine approach and its implications in cochlear implantation

The most frequent sequelae following a translabyrinthine approach for vestibular schwannoma resection is complete hearing loss on the affected side. Such patients could benefit from a cochlear implant, provided that two essential requisites are met before surgery: a preserved cochlear nerve and a patent cochlea to accommodate the electrode array. The goal of our study is to determine the prevalence and extent of cochlear ossification following a translabyrinthine approach. Postoperative MRI of 41 patients were retrospectively reviewed. Patients were classified according to the degree of cochlear obliteration into three groups (patent cochlea, partially obliterated cochlea and totally obliterated cochlea). The interval between surgery and the first MRI was studied as well as its relationship with the rate of cochlear ossification. At first postoperative MRI (mean interval of 20 months), 78% of patients showed some degree of cochlear ossification. Differences were found in the time interval between surgery and first MRI for each group, showing a smaller interval of time the patent cochlea group (p > 0.05). When MRI was performed before the first year after surgery, a larger rate of patent cochlea was found (p > 0.05). The present study suggests that cochlear ossification is a time-depending process, whose grounds are still to be defined.

Treatment of Temporal Bone Fractures

Traumatic injury to the temporal bone can lead to significant morbidity or mortality and knowledge of the pertinent anatomy, pathophysiology of injury, and appropriate management strategies is critical for successful recovery and rehabilitation of such injured patients. Most temporal bone fractures are caused by motor vehicle accidents. Temporal bone fractures are best classified as either otic capsule sparing or otic capsule disrupting-type fractures, as such classification correlates well with risk of concomitant functional complications. The most common complications of temporal bone fractures are facial nerve injury, cerebrospinal fluid (CSF) leak, and hearing loss. Assessment of facial nerve function as soon as possible following injury greatly facilitates clinical decision making. Use of prophylactic antibiotics in the setting of CSF leak is controversial; however, following critical analysis and interpretation of the existing classic and contemporary literature, we believe its use is absolutely warranted.

Subtotal Petrosectomy for Cochlear Implantation

Objectives:

The purpose of this study was to review the indications for subtotal petrosectomy for cochlear implantation, report our management of complications, as well as review those technical factors that are critical for successful implantation.

Methods:

Patients (n = 104) that underwent subtotal petrosectomy with closure of the external auditory canal and obliteration of the cavity with abdominal fat in combination with cochlear implantation were analyzed.

Results:

The most frequent indication for subtotal petrosectomy was the existence of a previous canal wall down technique. Postoperative complications occurred in 13 patients (11.83%). Extrusion of the device took place in 5 cases (4.55%).

Conclusions:

Subtotal petrosectomy in cochlear implantation permits obtaining a cavity isolated from the external environment, and when needed, it improves the access and visibility during the surgical procedure. Subtotal petrosectomy is a safe technique, with a low rate of complications.

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

OBJECTIVE

To describe the incidence and management of patients with facial nerve stimulation (FNS) associated with cochlear implant (CI) use in the setting of a prior temporal bone fracture.

PATIENTS

One adult CI recipient is reported who experienced implant associated FNS with a history of a temporal bone fracture. Additionally, a literature search was performed to identify similar patients from previous descriptions of CI related FNS.

MAIN OUTCOME MEASURES

Presence of FNS after implantation and ability to modify implant programming to avoid FNS.

RESULTS

The patient in the present report experienced FNS for middle and basal electrodes during intraoperative neural response telemetry (NRT) in the absence of any surgical exposure or manipulation of the facial nerve. FNS was absent during device activation, but it recurred during follow-up programming sessions. However, additional programming has prevented further FNS during regular implant use. Four other patients with FNS after temporal bone fracture were identified from the literature, and the present case represents the one of two cases in which reprogramming allowed for implant use without FNS.

CONCLUSIONS

CI associated FNS is uncommon in patients with a history of a temporal bone fracture, but it is likely that fracture lines provide a lower impedance pathway to the adjacent facial nerve and thus reduce the threshold for FNS. The present report suggests that, in the setting of a prior temporal bone fracture, NRT is not always a reliable predictor of FNS during implant use, and programming changes can help to mitigate FNS when it occurs.