Comparison of ABR and ASSR using narrow-band-chirp-stimuli in children with cochlear malformation and/or cochlear nerve hypoplasia suffering from severe/profound hearing loss

Objectives In pediatric audiology, objective techniques for hearing threshold estimation in infants and children with profound or severe hearing loss play a key role. Auditory brainstem responses (ABR) and auditory steady-state responses (ASSR) are available for frequency-dependent hearing threshold estimations and both techniques show strong correlations but sometimes with considerable differences. The aim of the study was to compare hearing threshold estimations in children with and without cochlear and cochlear nerve malformations. Methods Two groups with profound or severe hearing loss were retrospectively compared. In 20 ears (15 children) with malformation of the inner ear and/or cochlear nerve hypoplasia and a control group of 20 ears (11 children) without malformation, ABR were measured with the Interacoustics Eclipse EP25 ABR system® (Denmark) with narrow-band CE-chirps® at 500, 1000, 2000 and 4000 Hz and compared to ASSR at the same center frequencies under similar conditions. Results ABR and ASSR correlated significantly in both groups (r = 0.413 in malformation group, r = 0.82 in control group). The malformation group showed a significantly lower percentage of “equal” hearing threshold estimations than the control group. In detail, patients with isolated cochlear malformation did not differ significantly from the control group, whereas patients with cochlear nerve hypoplasia showed significantly greater differences. Conclusion ABR and ASSR should be used jointly in the diagnostic approach in children with suspected profound or severe hearing loss. A great difference in hearing threshold estimation between these techniques could hint at the involvement of cochlear nerve or cochlear nerve hypoplasia itself.

Új műtéti képalkotó lehetőség a belsőfül-implantátum elektródasorának dinamikus helyzetmeghatározására

Összefoglaló. Bevezetés: A cochlearis implantátum egy műtétileg behelyezett elektromos eszköz, amely az akusztikus hanghullámokat elektromos jelekké alakítja, közvetlenül a hallóideget stimulálja, így segíti a súlyos fokú hallássérüléssel vagy teljes hallásvesztéssel élők életét. Cochlearis implantációt követően a legjobb rehabilitációs eredmény elérésének technikai feltétele többek között az esetre szabott elektródaválasztás és az elektródasor teljes, kontrollált, szövődménymentes bejuttatása a scala tympaniba, miközben a cochlea belső struktúrája a lehető legkisebb mértékben sérül. A rutin intraoperatív elektrofiziológiai tesztek fontos információt adnak a készülék működőképességéről és a hallóideg stimulációjáról, azonban nem hagyatkozhatunk rájuk az elektródasor cochleán belüli helyzetének igazolásában. Mivel előfordulhat, hogy a rendelkezésre álló elektrofiziológiai vizsgálatok eredménye megfelelő, és mégis rendellenes helyzetbe kerül az elektróda, az arany standardot a képalkotó vizsgálatok jelentik. Módszer: Közleményünkben egy modern, hibrid műtő által nyújtott technológiai háttér új alkalmazási területét mutatjuk be. Szimultán kétoldali cochlearis implantációt végeztünk Cochlear Nucleus Slim Modiolar típusú perimodiolaris elektródasorral, a belső fül fejlődési rendellenességével rendelkező betegen. Az intraoperatív képalkotást Siemens Artis pheno C-karos robot digitális szubtrakciós angiográfiás rendszer biztosította valós idejű átvilágító és volumentomográfiás funkcióval. Eredmények: Az intraoperatív képalkotás által dinamikusan követhető az elektródasor bevezetésének folyamata, ellenőrizhető az elektródasor statikus helyzete, így kiváltható a rutinnak számító posztoperatív képalkotó vizsgálat. A rendellenes helyzetbe kerülő elektródasor pozíciója egy ülésben korrigálható, az újból bevezethető, így elkerülhető az újabb altatással járó, bizonytalan kimenetelű revíziós műtét. Következtetés: A hibrid műtő jól kontrollált, minimálisan invazív eljárások elvégzését biztosítja. Különösen a hallószerv fejlődési rendellenessége vagy egyéb, az elektródának a cochleába vezetését nehezítő rendellenesség esetén javasolt a műtői képalkotó diagnosztika. Orv Hetil. 2021; 162(22): 878–883. Summary. Introduction: The cochlear implant is a surgically inserted electrical device that converts acoustic sound waves into electrical signals to stimulate the cochlear nerve, thus helps the rehabilitation of people with severe to total hearing loss. One of the most important technical conditions for achieving the best rehabilitation result after cochlear implantation is the personalized choice of electrodes. Additionally, it is vital that there is a complete, controlled, uncomplicated delivery of the electrode array to the scala tympani while minimizing damage to the inner structures of the cochlea. Routine electrophysiological tests provide important information about device functionality and auditory nerve stimulation. However, they probably do not show an abnormal position of the electrode array within the cochlea. Thus, imaging studies remain the gold standard. Method: In our paper, we present a novel application field of the modern technological background provided by a hybrid operating room. Simultaneous bilateral cochlear implantation was performed with cochlear implants with perimodiolar electrode array (Nucleus Slim Modiolar) in a patient with cochlear malformation. Intraoperative imaging was provided by a Siemens Artis pheno C-arm robot digital subtraction angiography system with real-time fluoroscopy and volume tomography function. Results: Intraoperative imaging ensures dynamic follow-up of the introduction and static determination of the position of the electrode array and replaces routine postoperative imaging. If the electrode array was inserted in an abnormal position, the revision can be performed in the same sitting. Also, the revision surgery with a potential risk of uncertain outcome, alongside additional anaesthesia, can be prevented. Conclusion: The hybrid operating room ensures that well-controlled, minimally invasive procedures are performed. Intraoperative imaging can be imperative in malformed cochleae and conditions that may complicate electrode insertion. Orv Hetil. 2021; 162(22): 878–883.

Variation of the cochlear anatomy and cochlea duct length: analysis with a new tablet-based software

Purpose In cochlear implantation, thorough preoperative planning together with measurement of the cochlear duct length (CDL) assists in choosing the correct electrode length. For measuring the CDL, different techniques have been introduced in the past century along with the then available technology. A tablet-based software offers an easy and intuitive way to visualize and analyze the anatomy of the temporal bone, its proportions and measure the CDL. Therefore, we investigated the calculation technique of the CDL via a tablet-based software on our own cohort retrospectively. Methods One hundred and eight preoperative computed tomography scans of the temporal bone (slice thickness < 0.7 mm) of already implanted FLEX28™ and FLEXSOFT™ patients were found eligible for analysis with the OTOPLAN software. Measurements were performed by two trained investigators independently. CDL, angular insertion depth (AID), and cochlear coverage were calculated and compared between groups of electrode types, sex, sides, and age. Results Mean CDL was 36.2 ± 1.8 mm with significant differences between sex (female: 35.8 ± 0.3 mm; male: 36.5 ± 0.2 mm; p = 0.037), but none concerning side or age. Differences in mean AID (FLEX28: 525.4 ± 46.4°; FLEXSOFT: 615.4 ± 47.6°), and cochlear coverage (FLEX28: 63.9 ± 5.6%; FLEXSOFT: 75.8 ± 4.3%) were significant (p < 0.001). Conclusion A broad range of CDL was observed with significant larger values in male, but no significant differences concerning side or age. Almost every cochlea was measured longer than 31.0 mm. Preoperative assessment aids in prevention of complications (incomplete insertion, kinking, tipfoldover), attempt of atraumatic insertion, and addressing individual necessities (hearing preservation, cochlear malformation). The preferred AID of 720° (two turns of the cochlea) was never reached, opening the discussion for the requirement of longer CI-electrodes versus a debatable audiological benefit for the patient in his/her everyday life.

Lack of collagen α6(IV) chain in mice does not cause severe-to-profound hearing loss or cochlear malformation, a distinct phenotype from nonsyndromic hearing loss with COL4A6 missense mutation

Congenital hearing loss affects 1 in every 1000 births, with genetic mutations contributing to more than 50% of all cases. X-linked nonsyndromic hereditary hearing loss is associated with six loci (DFNX1-6) and five genes. Recently, the missense mutation (c.1771G>A, p.Gly591Ser) in COL4A6, encoding the basement membrane (BM) collagen α6(IV) chain, was shown to be associated with X-linked congenital nonsyndromic hearing loss with cochlear malformation. However, the mechanism by which the COL4A6 mutation impacts hereditary hearing loss has not yet been elucidated. Herein, we investigated Col4a6 knockout (KO) effects on hearing function and cochlear formation in mice. Immunohistochemistry showed that the collagen α6(IV) chain was distributed throughout the mouse cochlea within subepithelial BMs underlying the interdental cells, inner sulcus cells, basilar membrane, outer sulcus cells, root cells, Reissner’s membrane, and perivascular BMs in the spiral limbus, spiral ligament, and stria vascularis. However, the click-evoked auditory brainstem response analysis did not show significant changes in the hearing threshold of Col4a6 KO mice compared with wild-type (WT) mice with the same genetic background. In addition, the cochlear structures of Col4a6 KO mice did not exhibit morphological alterations, according to the results of high-resolution micro-computed tomography and histology. Hence, loss of Col4a6 gene expression in mice showed normal click ABR thresholds and normal cochlear formation, which differs from humans with the COL4A6 missense mutation c.1771G>A, p.Gly591Ser. Therefore, the deleterious effects in the auditory system caused by the missense mutation in COL4A6 are likely due to the dominant-negative effects of the α6(IV) chain and/or α5α6α5(IV) heterotrimer with an aberrant structure that would not occur in cases with loss of gene expression.

TIGA KASUS IMPLAN KOKLEA PADA DISPLASIA MONDINI

Mondini dysplasia is a kind of cochlear malformation caused by a failure growth of cochlea in the seventh week of pregnancy, results in cochlear turn which only reaches 1,5 turn until less than 2,5 turn. There is sensorineural hearing loss in Mondini dysplasia caused by anatomical malformation. The diagnosis of Mondini dysplasia is made by accurate anamnesis, audiology assessments and imaging results. This case study explains the importance of the holistic process of diagnosis and treatment of Mondini's dysplasia. Purpose: To explain that Mondini dysplasia should be diagnosed immediately and given the cochlear implant. Cases: There had been reported three cases of cochlear malformation of Mondini dysplasi type. They were first diagnosed with sensorineural hearing loss and speech delay in the age of 2-4 years. After had been done sequence of audiology assessments and imaging CT-scan and MRI simultaneously there were obtained that those three patients had Mondini dysplasia. Case Management: The use of hearing aid in those three patients had no effectiveness that brought them to the decision of cochlear implantation. Cochlear implant became such a great challenge even through for experienced physicians considering the scarcity of the case and the risk for complications like pelymph gusher and incorrect insertion of electrode. Cochlear implant surgeries had been done to those three patients with carefu consideration and the selection for appropriate type of electrode. On the first case there had been applied right ear cochlear implant, on the second case was bilateral, and on the third case was in the left ear. Complications of the surgeries were bleeding and perilymph gusher but they had been solved properly. Electrode insertion in all three cases had been placed correctly. Conclusion: Found three cases of Mondini dysplasia with symptoms of bilateral hearing loss, speech development, bilateral Mondini dysplasia, techniques and complications of cochlear implants. These three cases differ in the shape, width and size of the cochlear anatomy if they are studied more specifically. Two cases of unilateral cochlear implant placement and one bilateral case.

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.

Auditory Skills following Cochlear Implantation in Children with the Charge Syndrome

Objectives: To assess the auditory outcomes and skills of pediatric cochlear implant (CI) users with the CHARGE syndrome. To determine the influence of inner ear malformations on the surgical procedure and speech understanding outcomes in this population. Study Design: Observational, retrospective study. Materials and Methods: Imaging, auditory testing, intraoperative findings, complications, and postoperative auditory skills and outcomes of pediatric CI users with CHARGE syndrome were recorded. Results: 6 children (8 ears) were included, 5 of whom had prelingual deafness. Their mean age at implantation was 37 months. Six of the 8 ears presented cochlear malformation; the most frequent was hypoplasia type III. Intraoperatively, the transmastoid facial recess approach was used in 5 ears, and abnormalities of facial nerve anatomy were found in 5 ears. All electrode insertions were complete. All children were, to a varying degree, able to detect and identify sound. Verbalization skills were developed by 2 children, 1 of whom used oral language as his primary mode of communication. Conclusions: Cochlear implantation performed by an experienced surgeon in patients with the CHARGE syndrome is a safe procedure with adequate treatment planning. All children had improved auditory skills although the improvement was variable.

Cochlear Nerve Hypoplasia: Audiological Characteristics in Children and Adults

Background: Cochlear nerve deficiency is a general term used to describe both cochlear nerve hypoplasia (CNH) and cochlear nerve aplasia. Although these two conditions can have similar results on audiological evaluation, CNH yields more variation in audiological tests. Objectives: To describe the audiological characteristics of the CNH cases in our series in relation to radiological findings. Methods: We reviewed the medical charts, audiological findings, and radiological findings on cases with CNH. We included cases with CNH in one ear or both ears. Out of 90 subjects with CNH, we included a total of 40 individuals (21 women and 19 men; 49 ears) in the current study. We reviewed and analyzed the participants’ audiological test results according to the radiological findings. Results: Cases with CNH showed variations according to the cochlear structure. There were 13 normal cochleae, 4 with incomplete partition type I, and 32 with cochlear hypoplasia. The accompanying cochlear apertures also showed variation: 17 were normal, 28 stenotic, and 4 aplastic cochlear apertures. The subjects displayed hearing loss ranging from moderate to profound; furthermore, 4 subjects had no response to sound whatsoever. The degree of hearing loss was not statistically significantly different with regard to the presence or absence of cochlear malformation with CNH (p > 0.005). We observed both sensorineural hearing loss and mixed-type hearing loss among the CNH cases. Conclusions: CNH is the presence of a cochlear nerve that is smaller in diameter than the facial nerve. It can be accompanied with other associated inner ear malformations of different degrees of severity. We observed degrees of hearing loss ranging from moderate to profound.