Measurements of normal inner ear on computed tomography in children with congenital sensorineural hearing loss

The objective of this study is to use standardized measurements of the inner ear to see whether there are subtle bony malformations in children with congenital sensorineural hearing loss (SNHL) whose temporal bone computed tomography (CT) are grossly normal. The study includes 45 ears with congenital SNHL and grossly normal temporal bone CT scans and 45 ears with normal inner ear structures and normal hearing. Standardized measurements of the inner ear structures were made on axial temporal bone CT scans. Student’s t test was performed to compare the measurements of the two groups. There were significant differences in the measurements of the bony island width of the superior semicircular canal, bony island width of the lateral semicircular canal and maximal height of cochlea between two groups (P < 0.05). In conclusion, standardized measurements of bony labyrinth of inner ear on temporal bone CT can identify subtle abnormalities of inner ear in patients with congenital SNHL having grossly normal radiological images.     

Two temporal bone computed tomography measurements increase recognition of malformations and predict sensorineural hearing loss

OBJECTIVES/HYPOTHESIS: The objectives of this prospective study were to assess the reproducibility of the measurements of the cochlea and lateral semicircular canal (LSCC) and to determine if abnormal measurements predict sensorineural hearing loss (SNHL). METHODS: Two readers independently measured the cochlear height on coronal section and the LSCC bony island width on axial section on 109 temporal bone computed tomography scans; audiologic data on these patients were collected independently from medical records. Inter- and intrareader variability was evaluated using intraclass correlation coefficients (ICCs) based on a random-effects model. The positive and negative predictive values of abnormal measurement for hearing loss were determined. RESULTS: There was excellent inter- and intraobserver agreement for both measurements (ICC >80%). The average cochlear height was 5.1 mm (normal range, 4.4-5.9 mm) and average LSCC bony island width was 3.7 mm (normal range, 2.6-4.8 mm). Review of the original radiology reports demonstrated that both cochlear hypoplasia and LSSC dysplasia were overlooked in >50% of patients with both abnormal measurements and SNHL. Cochlear hypoplasia (< 4.4 mm) had a positive predictive value of 100% for SNHL, whereas cochlear hyperplasia and bony island dysplasia were less predictive. CONCLUSION: The measurements of coronal cochlear height and axial LSCC bony width have excellent reproducibility and identify bony labyrinth abnormalities missed by visual inspection alone. In addition, cochlear hypoplasia is highly predictive of SNHL. To reliably identify inner ear malformations, measurement of the cochlear height and LSCC bony island width, in addition to the vestibular aqueduct, should be routinely performed on all temporal bone studies.     

Computed tomography demonstrates abnormalities of contralateral ear in subjects with unilateral sensorineural hearing loss

Purpose

Prior studies have associated gross inner ear abnormalities with pediatric sensorineural hearing loss (SNHL) using computed tomography (CT). No studies to date have specifically investigated morphologic inner ear abnormalities involving the contralateral unaffected ear in patients with unilateral SNHL. The purpose of this study is to evaluate contralateral inner ear structures of subjects with unilateral SNHL but no grossly abnormal findings on CT.

Materials and methods

IRB-approved retrospective analysis of pediatric temporal bone CT scans. 97 temporal bone CT scans, previously interpreted as “normal” based upon previously accepted guidelines by board certified neuroradiologists, were assessed using 12 measurements of the semicircular canals, cochlea and vestibule. The control-group consisted of 72 “normal” temporal bone CTs with underlying SNHL in the subject excluded. The study-group consisted of 25 normal-hearing contralateral temporal bones in subjects with unilateral SNHL. Multivariate analysis of covariance (MANCOVA) was then conducted to evaluate for differences between the study and control group.

Results

Cochlea basal turn lumen width was significantly greater in magnitude and central lucency of the lateral semicircular canal bony island was significantly lower in density for audiometrically normal ears of subjects with unilateral SNHL compared to controls.

Conclusion

Abnormalities of the inner ear were present in the contralateral audiometrically normal ears of subjects with unilateral SNHL. These data suggest that patients with unilateral SNHL may have a more pervasive disease process that results in abnormalities of both ears. The findings of a cochlea basal turn lumen width disparity >5% from “normal” and/or a lateral semicircular canal bony island central lucency disparity of >5% from “normal” may indicate inherent risk to the contralateral unaffected ear in pediatric patients with unilateral sensorineural hearing loss.     

Labyrinthine anomalies with normal cochlear function.

Three cases of labyrinthine anomaly confirmed by polytomography and CT scan are reported. They showed similar dysplasia of the bony labyrinth: dilation and fusion of the lateral semicircular canal (SCC) and of the vestibule with a normally shaped cochlea and other SCCs. One side was involved in 2 cases and both sides in 1 case. The 1st case showed normal hearing levels with markedly reduced response to caloric stimulation in the affected ear. The 2nd case showed conductive hearing loss due to cholesteatoma with normal bone conduction hearing levels and normal caloric response. The 3rd case showed bilateral conductive hearing loss of unknown cause. The classification of labyrinthine anomalies and labyrinthine functions is discussed. Labyrinthine anomaly detected by CT scan and polytomography can be present in patients with normal cochlear and/or vestibular function.     

Utility of temporal bone computed tomographic measurements in the evaluation of inner ear malformations

OBJECTIVE: To investigate whether normative inner ear measurements can assist in the evaluation of sensorineural hearing loss (SNHL). DESIGN: Retrospective cohort review. SETTING: A tertiary care hospital. PATIENTS: Computed tomography or magnetic resonance imaging was performed on 188 ears with SNHL and 220 ears without SNHL (204 children) between 2001 and 2004. INTERVENTION: Two readers measured the basal turn of cochlea (BTC) lumen, lateral semicircular canal (LSCC) bony island width, superior semicircular canal (SSCC) bony island width, and cochlear height (CH). MAIN OUTCOME MEASURES: A t test was performed comparing measurements in patients with and without SNHL. Interobserver variability was characterized by intraclass correlation coefficients and Bland-Altman plots. RESULTS: The t test results demonstrated no statistically significant differences between inner ear measurements in those with and without SNHL. The intraclass correlation coefficients for BTC lumen, CH, LSCC bony island width, and SSCC bony island width measurements was 0.612, 0.632, 0.869, and 0.912, respectively. Bland-Altman plots revealed systematic biases of 1%, 8%, 10%, and 21% for the BTC lumen, SSCC bony island width, LSCC bony island width, and CH measurements, respectively. CONCLUSIONS: Inner ear measurements in children with and without SNHL are not statistically different. Moreover, the measurements are difficult to interpret because while they demonstrate good reproducibility, they are susceptible to systematic biases. However, use of inner ear measurements is more sensitive in identifying vestibulocochlear dysplasias and should be considered to complement visual analysis.     

Study of systemic lupus erythematosus in temporal bones

Despite some reports of sensorineural hearing loss with systemic lupus erythematosus (SLE), its pathologic correlate has remained unidentified due to the scarcity of human temporal bone studies. We here present findings in 14 temporal bones from 7 patients with SLE, examined histologically and immunohistochemically for pathologic conditions in the cochlea that might relate to their otologic histories. Blue-staining concretions were seen in the stria vascularis of 6 ears. Most of the cases showed a loss of spiral ganglion cells, with various degrees of hair cell loss and atrophy of the stria vascularis. One ear demonstrated formation of fibrous tissue and bone throughout the cochlea, with complete loss of the membranous labyrinth. Cochlear hydrops was found in only 1 ear. These findings in temporal bones from patients with SLE are discussed in relation to autoimmune disease of the inner ear.     

CT of the temporal bone in the study of the inner ear structures in detection of the causes of neurosensory hypoacusis

Computed tomograms of the inner ear structures (n=175) of 150 patients (age 0-75 years) with unaffected temporal bones were studied in detail. It is shown that polyposition CT of the temporal bone is a non-invasive method of visualization of the osseous labyrinth structures: cochlea, vestibule, semicircular canals, aqueducts of the labyrinth and internal acoustic meatus which are reflected on tomograms in 100% cases irrespective of the patient age. Their age-related features are analysed. CT imaging was made in 65 patients with neurosensory hypoacusis of inherited and acquired genesis. The following causes of neurosensory hypoacusis and deafness were revealed: congenital malformation of the labyrinth of Mondini type, common cavity of the labyrinth, cochlear hypoplasia, dysplasia of the vestibule and semicircular canals, a wide aqueduct of the vestibule, stenosis of the internal acoustic meatus, bulboform enlargement of the inner acoustic meatus, neurinoma (schwannoma) of the hearing nerve, Langerhans-cell histiocytosis with affection of the labyrinth capsule, atypical cholesteatoma. The detected changes in the inner ear structures determine further treatment policy.     

Hearing in patients with congenital deformity of the inner ear.

Congenital abnormalities of the bony labyrinth and internal auditory meatus range from complete absence to minor anomalies compatible with normal cochlea function. A 'follow-up' survey to assess the hearing of 56 patients with abnormalities of the inner ear shown by tomography was made. The hearing levels are discussed in relation to the tomographic appearances and comparison made with other series of inner ear abnormalities demonstrated both radiographically and histologically.     

Hearing in patients with congenital deformity of the inner ear

Congenital abnormalities of the bony labyrinth and internal auditory meatus range from complete absence to minor anomalies compatible with normal cochlea function. A ‘follow-up’ survey to assess the hearing of 56 patients with abnormalities of the inner ear shown by tomography was made. The hearing levels are discussed in relation to the tomographic appearances and comparison made with other series of inner ear abnormalities demonstrated both radiographically and histologically.     

Cochlear nerve size evaluation in children with sensorineural hearing loss by high-resolution magnetic resonance imaging

PURPOSE: To determine differences in size of cochlear nerves among subjects with deafness due to connexin 26 (Cx26) mutations, subjects with deafness of unknown origin, and normal hearing subjects by sagittal high-resolution magnetic resonance (HRMR) imaging of the temporal bone. MATERIALS AND METHODS: Cross-sectional and surface areas and volumetric measurements of the cochlear nerve and modiolus were made on HRMR images of the internal auditory canal (IAC) and inner ear in the 3 groups of children (groups 1, 2, and 3). Three-way comparisons of in vivo cochlear nerve measurements on HRMR imaging were made among 17 children with sensorineural hearing loss (SNHL) and no obvious etiology for the hearing loss (group 1), 7 children with profound SNHL due to a Cx26 mutation (group 2), and 10 normal hearing children (group 3). RESULTS: Children with profound SNHL of unknown cause and children with profound SNHL due to a connexin mutation displayed hypoplastic cochlear nerves as compared with normal controls. HRMR imaging of the temporal bone was accurately delineated potential problems with cochlear nerves in 2 of 17 instances where high-resolution computed tomography did not do so. CONCLUSIONS: Accurate and specific measurements of the cochlear nerve and related structures is possible on HRMR imaging of the temporal bone. The size of the cochlear nerve is mildly hypoplastic in children with profound SNHL of unknown causes or children with a deafness-causing Cx26 mutation. HRMR imaging is superior to high-resolution computed tomography in the investigation of profound SNHL in children.     

Inner ear anomalies in cochlear implantees: importance of radiologic measurements in the classification.

OBJECTIVE: To classify the inner ear anomalies of cochlear implantees with profound sensorineural hearing loss. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: For the normative data of the inner ear structures, the temporal bone computed tomography of 60 patients (120 ears) with normal bone-conduction threshold (< 15 dB) were used, and the data were applied to 570 ears of 285 cochlear implantees. INTERVENTIONS: Predesignated inner ear structures were measured in temporal bone computed tomography images from the normal and cochlear implantation groups using a computer-based caliper that formed part of a picture archiving and communication system. MAIN OUTCOME MEASURES: The inner ear anomalies were defined when the structures presented visually obvious malformations or the measurements deviated 2 standard deviations from the means in the normative data. RESULTS: The application of normative data to 570 profound SNHL ears resulted in the identification of 293 individual anomalies in 127 anomalous ears. An enlarged vestibular aqueduct was the most common individual anomaly (49 cases), followed by vestibular enlargement (38 cases) and other semicircular canal dysplasia (37 cases). When the individual anomalies were reaccounted according to the more prominent anomaly where multiple anomalies were present in each ear, incomplete partition type II was the most common (34 ears), followed by cochlear hypoplasia (22 ears) and incomplete partition type I (20 ears). CONCLUSION: We suggested a measurement technique for the inner ear structures using computed tomography and derived normative measurements helpful for diagnosing inner ear anomalies. Using these normative data, we classified the inner ear anomalies of profound SNHL ears in cochlear implantees.     

Temporal bone findings on computed tomography imaging in branchio-oto-renal syndrome

OBJECTIVES/HYPOTHESIS: To describe temporal bone findings using visual inspection and direct measurement on computerized tomography (CT) in individuals with branchio-oto-renal syndrome (BOR). We ask if it is possible for the untrained observer to use a battery of CT observations as a tool in the overall evaluation of the BOR phenotype. STUDY DESIGN: Retrospective evaluation of CT findings in individuals with a clinical diagnosis of BOR based on criteria derived from genotype-phenotype analyses. METHODS: Prospective measurement of temporal bone CT imaging in 21 individuals (42 ears) with BOR and 21 normally hearing controls (21 ears) was performed. Thirty-nine aspects of each temporal bone were evaluated: 17 by direct measurement, 5 computed from direct measurement, and 17 by visual inspection. Thirty-eight recordings from each ear were made on axial section and 1 was made on coronal section. RESULTS: Statistically significant differences were found between BOR and control groups in 30 of 39 categories (76.9%). The most common and easily identifiable characteristics of BOR by visual inspection were 1) hypoplastic apical turn of the cochlea, 2) facial nerve deviated to the medial side of the cochlea, 3) funnel-shaped internal auditory canal, and 4) patulous eustachian tube. The embryological origin of temporal bone anomalies in BOR are described. CONCLUSIONS: CT evaluation of the temporal bone, when properly investigated, should be used as an important tool in the overall evaluation of the BOR phenotype.     

Expression of aquaporins in inner ear disease

The inner ear is responsible for hearing and balance and consists of a membranous labyrinth within a bony labyrinth. The balance structure is divided into the otolith organ that recognizes linear acceleration and the semicircular canal that is responsible for rotational movement. The cochlea is the hearing organ. The external and middle ear are covered with skin and mucosa, respectively, and the space is filled with air, whereas the inner ear is composed of endolymph and perilymph. The inner ear is a fluid-filled sensory organ composed of hair cells with cilia on the upper part of the cells that convert changes in sound energy and balance into electric energy through the hair cells to transmit signals to the auditory nerve through synapses. Aquaporins (AQPs) are a family of transmembrane proteins present in all species that can be roughly divided into three subfamilies according to structure and function: 1) classical AQP, 2) aquaglyceroporin, and 3) superaquaporin. Currently, the subfamily of mammalian species is known to include 13 AQP members (AQP0–AQP12). AQPs have a variety of functions depending on their structure and are related to inner ear diseases such as Meniere's disease, sensorineural hearing loss, and presbycusis. Additional studies on the relationship between the inner ear and AQPs may be helpful in the diagnosis and treatment of inner ear disease. Laryngoscope, 130:1532–1539, 2020     

Labyrinthine involvement in Langerhans' cell histiocytosis

BACKGROUND: Langerhans' cell histiocytosis, a rare condition caused by the proliferation of abnormal Langerhans' cells ('LCH cells') and an accompanying granulomatous infiltrate, can affect several organs including the ear. External and middle ear involvement are common with a reported incidence as high as 61%. The bony labyrinth is resistant to erosion by the granulation tissue, thereby protecting the cochlea and vestibular structures. Probably for this reason, involvement of the inner ear is rare, with few case reports in the literature. PATIENTS: We report two girls, one with bilateral and the other with unilateral mastoid involvement, in whom there was invasion of the labyrinth. The first girl had 'single system' LCH affecting only bone and developed an acute hearing loss due to invasion of the cochlea, while the second had both bone and skin involvement and labyrinthine involvement was diagnosed on imaging prior to the onset of labyrinthine symptoms. CONCLUSION: Inner ear involvement can lead to permanent deafness, which may be prevented by early institution of treatment. Threatened inner ear involvement requires urgent systemic medical therapy with steroids, possibly combined with chemotherapy.     

Normal anatomy of the inner ear.

The three parts of the inner ear have been reviewed: the membranous (endolymph containing) labyrinth surrounded by the osseous (perilymph containing) labyrinth, and the otic capsule of bone that encases the osseous labyrinth. This is a brief survey of the normal anatomy, but one must always remember that the hallmark of the temporal bone is variation.     

Traumatic perilymphatic fistulas in children: etiology, diagnosis and management

Post-traumatic perilymphatic fistulas have been described following ear and temporal bone injury, particularly in the setting of temporal bone fractures. However, indications for exploratory surgery in cases of trauma without temporal bone fracture are vague and not well described. We describe three children who presented with symptoms suggestive of perilymphatic fistula (PLF) without an associated temporal bone fracture: two with penetrating tympanic membrane injuries and one with blunt temporal bone trauma. All had symptoms of hearing loss and vestibular disturbance. Two of the children cooperated with ear-specific audiologic assessment, which demonstrated sensorineural hearing loss (SNHL) on the traumatized side. The third child showed audiometric evidence of a SNHL on the injured side, but due to his age, the degree of severity of the SNHL was unable to be appropriately addressed prior to the patient being surgically managed. All three children underwent exploratory surgery and were found to have bony defects in the region of the oval window. All were repaired with fascial grafts to the oval and round windows with complete resolution of vestibular symptoms. However, two of the three patients with documented post-operative audiograms suffered from persistent SNHL on the injured side. We conclude that exploratory middle ear surgery is indicated in patients suffering from blunt or penetrating temporal bone or middle ear trauma who demonstrate persistent vestibular symptoms, sensorineural hearing loss or radiographic evidence of oval window pathology. As this is a limited number of patients, a larger series may be warranted to study the actual incidence of post-traumatic PLF in the child with persistent hearing loss and vertigo after head or ear trauma.     

Concept and anatomical feasibility study of an "endosteal electrode" for bimodal stimulation in severely deaf ears

BACKGROUND: Many patients with severe hearing loss could benefit from a bimodal stimulation unilaterally: acoustically in the apical region of the cochlea with some residual low frequency hearing and electrically via a cochlear implant in the basal turn with lost high hearing in the high frequency range. As a new concept we introduce the idea of an "endosteal electrode" - to be inserted between spiral ligament and endosteum of the bony wall without opening the fluid-filled inner ear. In this paper the feasibility from the anatomical point of view is to be proven. MATERIALS AND METHODS: In 10 human temporal bone specimens the bone covering the membraneous inner ear is carefully removed in the site of a typical cochleostomy. It should by proven whether or not the soft tissue layer covering the inner ear could be left intact and, furthermore, whether a "dummy-electrode array" could be inserted "endosteally". RESULTS: In 10 of the 10 specimen the preparation could be carried out in the desired way, leaving the spiral ligament intact. The regular site of the "electrode" was morphologically proven after embedding the specimens for histological evaluation. CONCLUSIONS: From the anatomical point of view, an "endosteal cochlear implantation" seems feasible. Further experiments including animal studies must show, whether this concept might succeed functionally.     

Sensorineural and Conductive Hearing Loss Associated With Lateral Semicircular Canal Malformation

Objective Lateral semicircular canal (LSCC) malformation is one of the most common radiological inner ear malformations. Traditionally, inner ear malformations are thought to be associated with sensorineural hearing loss (SNHL). Recent experience with patients with LSCC malformation suggested that LSCC malformation may be associated with both SNHL and conductive hearing loss (CHL). The auditory phenotype associated with LSCC malformation is not well delineated. The objective of this study is to define the nature of the hearing loss associated with LSCC malformation. Study Design Retrospective review Methods Retrospective review of clinical records, audiological evaluation, and imaging studies. Results Two patients with unilateral and 13 patients with bilateral LSCC malformation were identified. LSCC malformation was associated with CHL in 14% (4 ears), SNHL in 71% (20 ears), normal hearing in 11% (3 ears) and CHL due to atresia in one ear. Hearing loss varied from mild to profound but did not correlate with the severity of LSCC malformation. In bilateral malformation, the hearing loss was asymmetric in half of the cases. Malformation of the posterior limb of the LSCC was always associated with a large vestibular aqueduct. An absent or rudimentary LSCC was invariably associated with a cochlear abnormality. Conclusions LSCC malformation, like other inner ear malformations such as large vestibular aqueduct and X‐linked mixed deafness with perilymph gusher, can be associated with CHL, SNHL, or normal hearing. Children with unexplained conductive hearing loss often undergo exploratory surgery to improve hearing. Given that inner ear malformations may be associated with a pure CHL, it is critical that children undergo computed tomography scan of the temporal bone prior to undergoing exploratory surgery.     

Magnetic resonance appearance of the inner ear after hearing-preservation surgery.

OBJECTIVE: To determine whether the appearance of the inner ear on T2-weighted follow-up magnetic resonance imaging correlates with hearing status after hearing-preservation surgery for vestibular schwannoma. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral medical center. PATIENTS: The study includes patients undergoing hearing-preservation surgery for vestibular schwannoma from 1998 to 2003. INTERVENTION: Diagnostic evaluation with magnetic resonance imaging and audiometric evaluation. MAIN OUTCOME MEASURES: Hearing results as reported in charts was correlated with appearance of membranous labyrinth on T2-weighted magnetic resonance images obtained at least 1 year after surgery. RESULTS: Twenty-nine patients were identified, 16 of whom satisfied the inclusion criteria. All 16 of the patients underwent middle fossa removal of vestibular schwannoma. Serviceable hearing according to American Academy of Otolaryngology-Head and Neck Surgery criteria was preserved in eight patients (50%). Of the eight patients without serviceable hearing, six had the cochlear nerve sacrificed at the time of surgery. All patients with serviceable hearing had normal appearing cochleovestibular signal on T2-weighted images, whereas six of eight patients (75%) with no hearing or poor hearing had abnormal low signal in the inner ear, suggesting inner ear ossification. The positive predictive value of a normal labyrinth for preserved hearing was 90%, whereas the negative predictive value of an abnormal labyrinth for no hearing was 100%. All but one patient who had the cochlear nerve sacrificed showed abnormal morphology of the labyrinth on T2-weighted magnetic resonance imaging. CONCLUSION: We describe the T2-weighted magnetic resonance findings after hearing-preservation surgery for acoustic tumor removal. Loss of inner ear signal on T2-weighted images correlates with loss of hearing postoperatively, whereas preserved inner ear signal correlates with hearing preservation after middle fossa surgery for vestibular schwannoma removal.