Severe Cochlear Malformations Research Articles

Cochlear reimplantation outcomes over 20 years: Expertise in reimplantation surgery and auditory-speech rehabilitation

ObjectivesThe aim of this study was to present an institution's experience with cochlear reimplantation (CRI), to assess surgical challenges and post-operative outcomes and to increase the success rate of CRI. Study designRetrospective single-institution study. SettingTertiary medical center. MethodsWe retrospectively evaluated data from 76 reimplantation cases treated in a tertiary center between 2001 and 2022. Clinical features including etiology of hearing loss, type of failure, surgical issues, and auditory speech performance were analyzed. Categorical Auditory Performance (CAP) and Speech Intelligibility Rating (SIR) scores were used to evaluate pre- and post-CRI outcomes. ResultsThe CRI population comprises of 7 patients from our institute,69 referred patients from other centers. Device failure was the most common reason (68/76, 89.5 %) for CRI; in addition, there were 7 medical failures and 1 had both soft device failure. Medical failures included flap rupture and device extrusion, magnet migration, auditory neuropathy, leukoencephalopathy, foreign-body residue and meningitis. In 21/76 patients, the electrode technology was upgraded. The mean time to failure was 0.58–13 years, with a mean of 4.97 years. The mean (± SD) CAP and SIR scores before and after CRI were 5.2 ± 1.2 versus 5.5 ± 1.1 and 3.4 ± 1.1 versus 3.5 ± 1.1, respectively. Performance was poor in six patients with severe cochlear malformation, auditory nerve dysplasia, leukoencephalopathy, and epilepsy. ConclusionCRI surgery is a challenging but relatively safe procedure, and most reimplanted patients experience favorable postoperative outcomes. Medical complications and intracochlear damage are the main causes of poor postoperative results. Therefore, adequate preoperative preparation and atraumatic CRI should be carried out for optimal results.

A New Treatment Option in Incomplete Partition Type III: The Varese Bone-Air Stimulation (B.A.S.).

The incomplete partition type III is a severe cochlear malformation present in X-linked deafness. It is a rare, non-syndromic cause of severe to profound mixed hearing loss, often progressive. The complete absence of bony modiolus and the wide communication between the cochlea and the internal auditory canal make cochlear implantation challenging, with still no consensus on the management of these patients. To the best of our knowledge, no results have ever been published in the literature on the treatment of these patients with hybrid stimulation (bone and air). We present three cases in which this hybrid stimulation gave better audiological results then air stimulation alone. A literature review on audiological results of the current treatment options in children affected by IPIII malformation was conducted independently by two researchers. Ethical considerations on the treatment of these patients were conducted by the Bioethics department of the University of Insubria. In two of the patients, the bone-air stimulation, associated with prosthetic-cognitive rehabilitation, meant that surgery was avoided, obtaining similar communication performances of those present in the literature. We believe that, when the bone threshold appears partially preserved, a stimulation through the bone or hybrid modality, such as the Varese B.A.S. stimulation, should be attempted.

Sensorineural hearing loss and hypoplastic cochlea in Axenfeld-Rieger syndrome with FOXC1 mutation

ObjectiveAxenfeld-Rieger syndrome (ARS) type 3 is a rare autosomal dominant disease, characterized by anterior segment dysgenesis of the eye, hearing loss, and cardiac defects. ARS type 3 is highly associated with FOXC1 mutations, which induces developmental disorders of neural crest cells. Most studies about ARS patients focused on ophthalmologic findings, but details in their hearing loss have not yet been revealed. In this report, we investigated audiological and otological manifestations in the ARS type 3 patient who had the novel heterozygous FOXC1 mutation leading deletion at the forkhead DNA-binding domain. Methods and ResultsPure tone audiometry showed bilateral sensorineural hearing loss (SNHL) and audiological examinations confirmed that major dysfunctions existed in the cochlea, rather than the spiral ganglion neurons and the cochlear nerve. CT and MRI revealed the hypoplastic cochlea at both sides. Given that the 6p25 deletion syndrome, lacking one allele of the FOXC1 gene, shows similar, but more severe cochlear malformations than the present case, the FOXC1 mutations might contribute to the hypoplasia and dysfunctions in the cochlea. ConclusionTo our knowledge, this is the first report demonstrating that the ARS type 3 patient with the FOXC1 mutation has the hypoplasia and dysfunctions in the cochlea, which results in bilateral SNHL.

Auditory Brainstem Implantation: An Overview

An auditory brainstem implant (ABI) is a surgically implanted central neural auditory prosthesis for the treatment of profound sensorineural hearing loss in children and adults who are not cochlear implant candidates due to a lack of anatomically intact cochlear nerves or implantable cochleae. The device consists of a multielectrode surface array which is placed within the lateral recess of the fourth ventricle along the brainstem and directly stimulates the cochlear nucleus, thereby bypassing the peripheral auditory system. In the United States, candidacy criteria for ABI include deaf patients with neurofibromatosis type 2 (NF2) who are 12 years or older undergoing first- or second-side vestibular schwannoma resection. In recent years, several non-NF2 indications for ABI have been explored, including bilateral cochlear nerve avulsion from trauma, complete ossification of the cochlea due to meningitis, or a severe cochlear malformation not amenable to cochlear implantation. In addition, growing experience with ABI in infants and children has been documented with encouraging outcomes. While cochlear implantation generally remains the first-line option for hearing rehabilitation in NF2 patients with stable tumors or post hearing preservation surgery where hearing is lost but a cochlear nerve remains accessible for stimulation, an ABI is the next alternative in cases where the cochlear nerve is absent and/or if the cochlea cannot be implanted. Herein, we review ABI device design, clinical evaluation, indications, operative technique, and outcomes as it relates to lateral skull base pathology.

Pediatric Auditory Brainstem Implantation: Impact on Audiological Rehabilitation and Tonal Language Development

Objective: This is a retrospective review of the impact of an Auditory Brainstem Implant (ABI) on the audiological rehabilitation and tonal language development of pediatric patients with prelingual profound deafness in Hong Kong. Results: From January 2009 to February 2015, 11 pediatric patients with profound prelingual deafness received an ABI in Hong Kong (age range 1.67–3.75 years). Etiologies included Cochlear Nerve Deficiency in 7, Severe Cochlear Malformations in 2, and Retrocochlear Deafness in 2. All of them were rehabilitated in Cantonese, a dialect of Chinese. Standard pediatric cochlear implant outcome measurements were used in this study that comprised of the 7-Sound Detection, Syllable Identification, Vowel Identification, Consonant Identification, Tone Imitation, Tone Production and Speech Perception Category. Audiological rehabilitation and speech development outcomes were reviewed. Age-matched outcomes of pediatric cochlear implant users were used for comparisons. Conclusion: Encouraging results of speech development were found, especially with continued use of the ABI. There was considerable variation in outcomes. Children with coexisting developmental and nonauditory cognitive disabilities did not perform as well. Auditory brainstem implantation is a safe and beneficial treatment for profound prelingual deafness in Cantonese-speaking pediatric patients.

Complications of Pediatric Auditory Brain Stem Implantation via Retrosigmoid Approach

Objective: We aimed to present the complications of auditory brain stem implantations (ABI) in pediatric patients which were performed via retrosigmoid approach. Methods: Between March 2007 and February 2010, five prelingually deaf children underwent ABI (Medel device) operation via retrosigmoid approach. All children had severe cochlear malformations. The ages ranged from 20 months to 5 years. The perioperative complications encountered in 2 patients were evaluated retrospectively. Results: No intraoperative complication was observed in the patients. Cerebrospinal fluid (CSF) leakage was the most common postoperative complication that was seen in 2 patients. The CSF leak triggered a cascade of comorbidities, and elongated the hospitalization. Conclusion: Pediatric ABI surgery can lead to morbidity. The CSF leak is the most common complication encountered in retrosigmoid approach. The other complications usually result from long-term hospital stay during treatment period of the CSF leak. Therefore, every attempt must be made to prevent occurrence of CSF leaks in pediatric ABI operations.

Imaging in 28 children with cochlear nerve aplasia

Conclusion. Preoperative CT and MRI assessment of children with severe or profound sensorineural hearing loss (SNHL) is critical for determining implant candidacy. Objectives. There are a significant number of children who do not show any auditory development with a cochlear implant (CI), possibly due to cochlear nerve (CN) aplasia/hypoplasia. Regardless of the suspected etiology, if a CI is not providing auditory development the clinician should carefully evaluate the possibility of a CN malformation and re-evaluate the child with detailed neuroimaging studies. If the imaging evaluation shows severe cochlear malformation or CN aplasia there is some developmental urgency to consider auditory brainstem implant (ABI) surgery. Subjects and methods. Twenty-eight children affected by congenital SNHL were examined by CT and MRI. Evaluation of the cerebellopontine angle (CPA), internal auditory canal (IAC), cranial nerves, and membranous labyrinth was performed. Six children had been previously fitted elsewhere with a CI with no sound detection. Results. Suspected congenital anomalies were confirmed by CT and MRI in all 28 children: 16 with associated labyrinthine malformations; 1 with outer, middle, and inner ear malformations; and 2 with associated monolateral facial nerve aplasia.

Clinical Performance of Children Following Revision Surgery for a Cochlear Implant

The purpose of this study was to describe the causes for revision surgery and to compare clinical performance before and after surgery in children who required electrode reinsertion. Soundfield thresholds and speech recognition scores were compared before device failure and following electrode reinsertion. Temporal bones from a deceased adult implant user who underwent bilateral revision implantation were analyzed. Histopathology in the adult temporal bones revealed new bone formation in the scala tympani and substantially reduced spiral ganglion counts, with open-set speech recognition realized. Of 28 children undergoing revision surgery, 18 required electrode reinsertion. With the exception of 1 patient with severe cochlear malformation, new electrode arrays were fully inserted without difficulty. Clinical outcomes between pre-device failure and post-electrode reinsertion did not differ statistically. Electrode reinsertion is technically feasible in the pediatric population. The majority of children recover their prerevision clinical performance. C-4.

Congenital malformation of the inner ear and pediatric cochlear implantation.

To study the surgical aspects and performance outcome of cochlear implantation in children with malformed inner ears. Clinical and audiometric evaluation in 13 patients. Patient data concerning surgery, postoperative follow-up, and pre- and postimplantation audiometry were obtained from the cochlear implant center's database and evaluated. A review of the literature has been included. Tertiary referral center. The patients had a variety of inner ear malformations and profound hearing loss. One patient with recurrent meningitis had a severe cochlear malformation (common cavity). Major complications did not occur. In one patient with an abnormal position of the cochlea and concurring middle ear disease, it was difficult to find the scala tympani during surgery. A cerebrospinal fluid gusher was encountered in two patients and an aberrant facial nerve in another, which did not lead to any complications. The patients with mild cochlear malformation such as an incomplete partition demonstrated a good performance in speech perception tests. Even the child with the common cavity deformity had some open-set speech perception 1 year after implantation. Viewing the patients from this study and patients from a review of the literature concerning cochlear implantation in children with malformed inner ears including severe cochlear malformations, the occurrence of an aberrant facial nerve was 17%, which increases to 27% if one reviews the surgical findings in children with severe malformed cochleae such as a common cavity or a severe cochlear hypoplasia. In the latter patients, results in speech perception vary. Although the result of cochlear implantation may be promising, as in our patient with a common cavity, during preoperative counseling the child's parents must be informed that the result is uncertain.

Fluoroscopically assisted cochlear implantation.

Real-time intraoperative fluoroscopy is a useful adjunct to cochlear implantation in selected cases. The advantages include the avoidance of complications such as extracochlear array placement, intrameatal array insertion, and avoidance of significant bending or kinking. This is particularly useful when implanting a severely abnormal cochlea. The technique was initially developed for laboratory study of electrode prototypes in cadaver temporal bones to evaluate insertion dynamics and mechanisms of intracochlear trauma. The technique was subsequently adapted for use in live surgeries. Live surgeries were performed using fluoroscopic guidance on nine patients. Five patients were implanted with the Nucleus 24 RCS during preclinical trials. Two patients with severe cochlear malformations were implanted with a Nucleus CI24M straight array. Two patients with severe cochlear ossification were implanted with the Nucleus CI24 double array. Appropriate insertions were achieved without electrode damage in all cases. Intraoperative fluoroscopy is a useful adjunct to cochlear implantation, which can be performed with minimum risk to the patient and operating room staff if the outlined precautions are taken. Intraoperative fluoroscopy is indicated in cases where the intracochlear behavior of the electrode array cannot be predicted, a condition encountered when implanting new electrode designs, cases with severely malformed inner ears, or cases of severe intraluminal obstruction requiring a double-array insertion.

Hearing habilitation with auditory brainstem implantation in two children with cochlear nerve aplasia

Patients with aplasia and hypoplasia of the cochlear nerve have no chance of having their hearing restored by stimulating the periphery of the auditory system using the traditional cochlear implant. A possible approach to auditory rehabilitation may be direct electrical stimulation of the cochlear nuclei with an auditory brainstem implant (ABI). Recently, two children, aged 4 and 3 years, respectively, with bilateral severe cochlear malformations and cochlear nerve aplasia received an ABI. The present paper reports the technique and the preliminary results of this experience. The classic retrosigmoid approach was used. The correct position of the electrodes was estimated with the aid of EABRs and neural response telemetry (NRT). No postoperative complications were observed. High-resolution CT scans with a bone algorithm reconstruction technique were taken postoperatively to evaluate electrode placement before discharge. The ABI was activated 30 days after implantation in both patients. To date 16 and 13 electrodes, respectively, have been activated in the two children. Three months after activation the first patient had achieved good environmental sound awareness, good speech detection and some speech discrimination. The second child, 1 month after activation, had achieved good environmental sound awareness and moderate speech detection. To the best of our knowledge this is the first report of patients with hypoplasia of the cochlea and aplasia of the cochlear nerve, aged below 5 years and treated with an ABI.