Bilateral superior semicircular canal dehiscence: bilateral conductive hearing loss with subtle vestibular symptoms

Superior semicircular canal dehiscence is caused by a bone defect on the roof of the superior semicircular canal. The estimated prevalence when unilateral varies between 0.4% and 0.7% and is still unknown when bilateral. Patients may present with audiologic and vestibular symptoms that may vary from asymptomatic to disabling. We report a case of a 72-year-old Caucasian woman presented to otolaryngology department reporting imbalance, bilateral pulsatile tinnitus, hypoacusis while being very sensitive to certain sounds. Physical examination was unremarkable, except for the Rinne test that was negative in both sides. The patient underwent an audiometry revealing a mild bilateral conductive hearing loss. A temporal bone CT scan was performed which evidenced bilateral superior semicircular canal dehiscence. Cervical vestibular evoked myogenic potentials and electrocochleography confirmed diagnosis. Although rare, superior semicircular canal dehiscence shall be considered in conductive hearing loss with vestibular symptoms.

The influence of the subarcuate artery in the superior semicircular canal dehiscence and its frequency on stillbirths: illustrative cases and systematic review

Literature describes that on the 25th gestational week the labyrinth is fully formed and with adult size. However, recent studies have shown that the cranial and labyrinth development continues until 3 years of age.

OBJECTIVES

To demonstrate through tomographic study the frequency of semicircular canal dehiscence on nine specimens of stillbirths between 32 and 40 weeks and, through literature review, present another possible etiology for its cause.

METHODS

Tomographic study of the temporal bone of 9 specimens of stillbirths between 32 and 40 weeks.

RESULTS

A frequency of 88.89% of alterations were found in our study, with 44% presenting bilateral alterations and 44% unilateral alteration; 11.11% had no dehiscence.

CONCLUSION

The tomographic study showed superior semicircular canal dehiscence (SSCD) in 88% of the specimens studied, protrusion of the superior semicircular canal (SSC) in all fetuses, and an enlarged SSC that may be caused by the expansion process provoked by the subarcuate artery entering the subarcuate canaliculus, leading to SSCD.

Superior canal dehiscence with tegmen defect revealed by otoscopy: Video clip demonstration of pulsatile tympanic membrane

Superior canal dehiscence is a pathologic condition of the otic capsule acting as aberrant window of the inner ear. It results in reduction of inner ear impedance and in abnormal exposure of the labyrinthine neuroepithelium to the action of the surrounding structures. The sum of these phenomena leads to the onset of typical cochleo-vestibular symptoms and signs. Among them, pulsatile tinnitus has been attributed to a direct transmission of intracranial vascular activities to labyrinthine fluids. We present the first video-otoscopic documentation of spontaneous pulse-synchronous movements of the tympanic membrane in two patients with superior canal dehiscence. Pulsating eardrum may represent an additional sign of third-mobile window lesion.

The Widely Patent Cochleovestibular Communication of Edward Cock is a Distinct Inner Ear Malformation: Implications for Cochlear Implantation

Objectives:

In 1838, Edward Cock described the anatomic findings in 4 inner ears with a widely patent communication between the cochlea and the vestibule that is now frequently referred to as the “common cavity deformity” and is often confused with Michel's “otocyst deformity.” Little is known about the anatomic characteristics, including the presence of neural elements in this malformation.

Methods:

Light microscopy and 2-dimensional and computerized 3-dimensional reconstructions were used to determine the histopathology and spiral ganglion cell counts in 7 temporal bones with a widely patent cochleovestibular communication.

Results:

In all 7 specimens, the cochlea, vestibule, and semicircular canals were distinguishable and a bony defect resulting in an abnormal communication of perilymphatic space between the cochlea and vestibule was present. The ductus reuniens was abnormally wide in all. The cochlear duct varied from less than 1 turn to up to 2 turns. The mean spiral ganglion cells were estimated as a percentage of age-matched normal controls at 2.3%, 16.5%, and 26.8% when the cochlea was approximately 1, 1½, and 2 turns, respectively (p = .007). The cribrose area consisted of a thin membrane in 2 specimens, and Rosenthal's canal openly communicated with the cerebrospinal fluid space in 3 specimens. The stapes footplate was abnormal in all 7 specimens and consisted of a central defect bridged by a thin membrane in 4 specimens. The facial nerve was dehiscent in 5 specimens (71%) and also followed an anomalous course in 2 specimens (28%).

Conclusions:

The widely patent cochleovestibular communication is a distinct inner ear malformation, recognition of which may have important clinical implications. Estimates of spiral ganglion cells can be predicted from the number of cochlear turns. Although cochlear implantation is feasible in patients with this malformation, a higher risk of cerebrospinal fluid gushers, facial nerve injuries, meningitis, and poor performance would be predicted. A better understanding of the anatomy will allow more effective surgical planning and techniques and may have a significant impact in improving outcomes.

Horizontal Canal Benign Positional Vertigo

The existence of horizontal canal benign positional vertigo (BPV) was predicted from temporal bone studies in 1973, but was not clinically confirmed until later. In this series of 300 patients with BPV, 35 (12%) were identified as having the horizontal canal variant. The essential features are the onset of vertigo when the patient assumes a supine position and bidirectional horizontal nystagmus as the head is turned from side to side. In one third it appeared as a canal “conversion” in patients undergoing repositioning treatment for posterior canal BPV. The mechanism can be canalithiasis or cupulolithiasis. Repositioning treatment is a 360° horizontal head and body rotation that has a high success rate if the symptomatic ear is correctly identified.

[Surgical approach of cochlear implantation in patients with common cavity]

OBJECTIVE

To discuss the surgical approach of cochlear implantation in patients with common cavity.

METHOD

Seventeen patients with common cavity underwent cochlear implantations through facial recess approach or transmastoid lateral semicircular canal approach,according to the preoperative imaging and audiological evaluation.

RESULT

Common cavity was opened and electrodes were inserted smoothly in all cases. Facial recess approach was used in 3 patients, while transmastoid lateral semicircular canal approach was used in the others. Intraoperative "gush" occurred in 4 cases. None of the cases developed intraoperative or postoperative complications, such as facial paralysis, meningitis and cerebrospinal fluid leakage. All cases had improvements in hearing. Atypical postoperative EABR responses were detected, the average free filed hearing threshold was 65 dB HL, the average speech recognition score of Chinese vowels was 75%, and the average speech recognition score of Chinese consonant was less than 10%.

CONCLUSION

(1) Selection of surgical approach for patients with common cavity: if the basal turn of cochlear could be distinguished at the posterior tympanum side of common cavity, the facial recess approach was used; if the cochlear,vestibule and the lateral semicircular canal merged to be a spherical cavity, the transmastoid lateral semicircular canal approach was used. (2) Surgical approach of cochlear implantation affected the postoperative outcomes. (3) Outcomes of cochlear implantation in common cavity patients were much poorer than normal cochlear cases.

High prevalence of inner-ear and/or internal auditory canal malformations in children with unilateral sensorineural hearing loss

OBJECTIVE

Radiological and genetic examination has recently advanced for diagnosis of congenital hearing loss. The aim of this study was to elucidate the prevalence of inner-ear and/or internal auditory canal malformations in children with unilateral sensorineural hearing loss (USNHL) for better management of hearing loss and genetic and lifestyle counseling.

METHODS

We conducted a retrospective study of charts and temporal bone computed tomography (CT) findings of 69 consecutive patients 0-15 years old with USNHL. In two cases, genetic examination was conducted.

RESULTS

Of these patients, 66.7% had inner-ear and/or internal auditory canal malformations. The prevalence of malformations in infants (age <1 year) was 84.6%, which was significantly higher than that in children 1-15 years old (55.8%; p<0.01). Almost half of the patients (32; 46.4%) had cochlear nerve canal stenosis; 13 of them had cochlear nerve canal stenosis alone, and in 19 it accompanied other malformations. Internal auditory canal malformations were observed in 22 subjects (31.8%), 14 (20.3%) had cochlear malformations, and 5 (7.2%) had vestibular/semicircular canal malformations. These anomalies were seen only in the affected ear, except in two of five patients with vestibular and/or semicircular canal malformations. Two patients (2.9%) had bilateral enlarged vestibular aqueducts. Mutations were found in SLC26A4 in one of the two patients with bilateral large vestibular aqueducts. The prevalence of a narrow internal auditory canal was significantly higher in subjects with cochlear nerve canal stenosis (50.0%) than in subjects with normal cochlear nerve canals (11.1%; p<0.01). There were no correlations between the type and number of malformations and hearing level.

CONCLUSIONS

The prevalence of inner-ear and/or internal auditory canal malformations detected by high-resolution temporal bone CT in children with USNHL was very high. Radiological and genetic examination provided important information to consider the pathogenesis and management of hearing loss. Temporal bone CT should be recommended to children with USNHL early in life. SLC26A4 mutation also should be examined in cases with bilateral enlarged vestibular aqueduct.

Mutation analysis of Netrin 1 and HMX3 genes in patients with superior semicircular canal dehiscence syndrome

CONCLUSION

In spite of its absence in the control population, there is questionable evidence for the alteration c.114C->T in the HMX3 gene being implicated in the development of superior semicircular canal dehiscence (SSCD). However, the concept of a complex disease is valid for SSCD and a possible molecular origin can neither be confirmed nor excluded by the results of this study.

OBJECTIVES

SSCD was first described in 1998 by Minor et al. While the etiology is not clear, findings from both temporal bone CT and histologic studies suggest a congenital or developmental origin. In recent years, a couple of genes regulating inner ear morphogenesis have been described. Specifically, Netrin-1 and HMX3 have been shown to be critically involved in the formation of the SCC. Molecular alterations in these two genes might lead to a disturbed development of this canal and might represent an explanation for SSCD.

METHODS

DNA was extracted from whole blood of 15 patients with SSCD. The coding sequences of Netrin-1 and HMX3 were amplified by PCR and sequenced.

RESULTS

One sequence alteration, heterozygous c.114C->T (conservative change without alteration of amino acid) in exon 1 of HMX3, was detected in 2 of 15 patients but not in 300 control chromosomes. The study was supported in part by the Emilia-Guggenheim-Schnurr-Foundation, Basel, Switzerland.

Bilateral posterior semicircular canal dehiscence in the setting of Hallermann-Streiff syndrome

Hallermann-Streiff syndrome, also known as oculomandibulofacial syndrome, is a rare congenital disorder affecting growth and cranial, dental, ocular, pilocutaneous, and mental development. In addition to routine audiologic testing in patients with this syndrome, high-resolution computed tomography of the temporal bones should be performed in those with documented or suspected sensorineural hearing loss. Cochlear implantation may be considered, as in other children with syndromic hearing loss and certain inner ear abnormalities, if the appropriate audiologic, psychosocial, and medical criteria are met. The current case report radiographically and clinically characterizes inner ear dysplasia in an 8-year-old patient with Hallermann-Streiff syndrome. High-resolution computed tomography of the temporal bones revealed a hypoplastic bony island between the vestibule and horizontal semicircular canals, as well as incomplete bony coverage of the posterior semicircular canal crura bilaterally. To our knowledge, this is the first report of a pediatric patient demonstrating bilateral posterior semicircular canal dehiscence.

[Vertigo due to enlarged vestibule with lateral semicircular canal dysplasia: an analysis of clinical characteristics]

OBJECTIVE

To explore the clinical characteristics and possible pathological mechanisms of vertigo due to enlarged vestibule with lateral semicircular canal dysplasia.

METHODS

A retrospective review was conducted for 5 cases of peripheral vertigo due to enlarged vestibule with lateral semicircular canal dysplasia. Their characteristics of medical history, precipitating factors, course of vertigo, auditory tests, vestibular tests and imaging examine results were analyzed.

RESULTS

The clinical characteristics were as follows. (1) Specifics of medical history: 4 cases suffered delays in gross motor development and potential equilibrium dysfunctions. One case failed to recount an earlier medical history, but could maintain normal hearing and vestibular functions for a long time in adulthood. (2) Most cases could identify the precipitating factors of initial attacks, such as head-bumping, nose-blowing and constipation, etc. resulting in sudden rises of intracranial or abdominal pressures. (3) Paroxysmal vertigo and progressive hearing loss were mimicking Meniere disease or large vestibular aqueduct syndrome. But its course of vertigo was different from those of Meniere disease and large vestibular aqueduct syndrome with regards to hearing levels and audiograms. (4) Some cases had positional vertigo. But the results of Dix-Hallpike and Roll tests were different from benign paroxysmal positioning vertigo (BPPV). (5) The inner ear imaging showed enlarged vestibule with lateral semicircular canal dysplasia.

CONCLUSION

The enlarged vestibule with lateral semicircular canal dysplasia is a rare etiology of peripheral vertigo. The history of delays in gross motor development and potential equilibrium dysfunctions in childhood may offer important diagnostic clues. And audiological and vestibular tests, high-resolution computed tomography and magnetic resonance may help to ascertain the diagnosis.

Genetic modification of the inner ear lateral semicircular canal phenotype of the Bmp4 haplo-insufficient mouse

In the mouse, development of the lateral semicircular canal of the inner ear is sensitive to Bmp4 heterozygosity. In the C57BL6 background 30% of the heterozygotes display circling behavior, 66% have a specific defect in the vestibular part of the inner ear, namely the constriction, interruption or absence of the lateral semicircular canal. Only mice having both ears affected display circling behavior. In the (C57BL6xCBA)N1 background, the penetrance of the canal phenotype is greatly reduced, and bilateral lateral canal defect is not sufficient to induce circling. We found association of the canal phenotype with the genotype of markers on chromosome 14 and 4, co-localizing with Ecs and Eclb identified in the Ecl mouse with similar lateral canal defects. Candidate genes to contain the causal mutation are Bmp4 on chromosome 14, and Rere on chromosome 4.

[The diagnostic value of multi-planar reconstruction in semicircular canals disease by HRCT]

OBJECTIVE

To study the diagnostic value of high-resolution computed tomography (HRCT) and multiplanar reconstruction (MPR) in assessment of semicircular canals disease.

METHOD

Eighty-three patients were scanned with HRCT and the original data were processed with MPR. The semicircular canals full length was respectively observed in one image of MPR in the normal ears. The abnormal location of the canal were observed.

RESULT

In one image the full length of the horizontal, superior and posterior semicircular canal can be respectively displayed in one image of MPR in normal ears. By this way ,1 superior semicircular canal dehiscence (SSCD)was found in precaution group, 1 superior and 2 horizontal semicircular canal blocked, 1 vestibular aqueduct (VA) joined into superior semicircular canal and 2 VAs joined into posterior semicircular canal and abnormity of the three semicircular canals were found in SNHL.

CONCLUSION

MPR canould display the three canals full length in one picture and have a high specificity in the diagnosis of the semicircular canal abnormity.

Congenital inner ear malformations without sensorineural hearing loss

It has been reported that normal hearing is rare in patients with severe inner ear vestibular malformations [Kokai H, Oohashi M, Ishikawa K, Harada K, Hiratsuka H, Ogasawara M et al. Clinical review of inner ear malformation. J Otolaryngol Jpn 2003;106(10):1038-44; Schuknecht HF. Mondini dysplasia. A clinical pathological study. Ann Otol Rhinol Laryngol 1980;89(Suppl. 65):1-23; Jackler RK, Luxford WM, House WF. Congenital malformations of the inner ear: a classification based on embryogenesis. Laryngoscope 1987;97:2-14; Phelps PD. Congenital lesions of the inner ear, demonstrated by tomography. Arch Otolaryngol 1974;100:11-8]. A 37-year-old woman had combined dysplasia of the posterior and lateral semicircular canals (PSCC, LSCC) with normal cochlear development and normal hearing in both ears. She had complained of dizziness for 8 months. High resolution computed tomography (CT) showed hypogenesis of the bony labyrinth in both ears. Bilateral PSCC and LSCC dysplasia and dilatation of the vestibule were detected. Magnetic resonant imaging (MRI) revealed that the deformity of the PSCC was more severe than the LSCC. Although the caloric test of the left ear elicited no nystagmus and there was reduced response in the right ear, the horizontal vestibulo-occular reflex (VOR) was present. Her dizzy sensation disappeared within 3 months without special treatment. The dizziness attack might have been caused by a temporary breakdown of her peripheral vestibular system.

[Diagnosis of superior semicircular canal dehiscence syndrome]

OBJECTIVE

To better understand superior semicircular canal dehiscence (SSCD) syndrome.

METHODS

A retrospective study was conducted on 6 patients who were diagnosed with SSCD syndrome in the Otology and Skull Base Surgery group of Fudan University. The clinical presentations including symptoms, signs, auditory tests and high resolution temporal bone computed tomography were reviewed.

RESULTS

Four patients presented with low frequency hearing loss while acoustic reflex responses were intact. Another patient was concomitance with chronic otitis media demonstrated profound sensorineural hearing loss. The sixth patient demonstrated normal hearing. Two patients also complained of autophony, but they were unable to tolerate their own voice. Five patients presented with vertigo while 2 patients were unable to tolerate the environmental noise. All patients showed slow component vertical torsional eye movement away from the effected eye which was induced by the presence of loud sound or pressure in the middle ear or valsalva maneuver. Four patients also demonstrated vertigo induced by the loud sound, 1 patient was induced head movement by 110 dB tone. All patients were revealed variable bone defect overlying on the SSC using high resolution temporal bone CT scan with SSC reformation.

CONCLUSIONS

The diagnosis of SSCD syndrome was established on both the presence of bone defect overlying superior semicircular canal which was demonstrated using high resolution temporal bone CT scan, and the presence of associated vestibular and auditory symptoms and signs.

[Indication and approach of cochlear implantation with common cavity]

OBJECTIVE

To discuss the indication and approach of cochlear implantation with common cavity inner ear malformation.

METHOD

Through imaging examination preoperatively for profound sensorineural hearing loss patients, we found 6 cases with common cavity inner ear malformation, in which cochlear, vestibule and lateral semicircular canal formed a big cavity. Among these cases, five had residual hearing, in the others, residual hearing was not detected.

RESULT

Among these cases with common cavity, 5 cases with residual hearing were treated with cochlear implantation, in 3 cases we selected round window approach, in the other 2 cases, we implanted the electrodes through the joint of the common cavity and posterior semicircular canal. Postoperatively, All these 5 patients have auditory response with cochlear implantation. The patient without residual hearing was not given cochlear implantation.

CONCLUSION

In patients with common cavity inner malformation, those who have residual hearing have indication for cochlear implantation, but it must be emphasized that their effect may not be as good as patients without inner ear malformation. In those patients without residual hearing, cochlear implantation should better not be performed.

Superior Canal Dehiscence Syndrome

The Superior Canal Dehiscence Syndrome (SCDS) was first reported by Minor at. Al. (1998), and has been characterized by vertigo and vertical-torsional eye movements related to loud sounds or stimuli that change middle ear or intracranial pressure. Hearing loss, for the most part with conductive patterns on audiometry, may be present in this syndrome. We performed a literature survey in order to to present symptoms, signs, diagnostic and therapeutic approaches to the SCDS, also aiming at stressing the great importance of including this syndrome among the tractable cause of vertigo. We should emphasize that this is a recent issue, still unknown by some specialists. The Correct SCDS diagnosis, besides enabling patient treatment, precludes misdiagnosis and inadequate therapeutic approaches.

How to prevent a stapes gusher

A stapes gusher is the result of a congenital inner ear anomaly showing at tone audiometry a conductive or mixed hearing loss. The conductive part of the hearing loss could lead to the thought to explore the middle ear. The congenital origin should lead to a high resolution. CT-scanning to evaluate a widening of the internal acoustic canal. Repeated audiometry could show especially a large conductive impairment in the lowest frequencies with a closure of the airbone gap at 2 khz and a high sensorineural high frequency loss at 4 and 8 khz. Contralateral stapedial reflexes may be present. Since the x-recessive mixed deafness syndrome (DFN3) frequently involves males with an early childhood hearing impairment, clinical suspicion should be high. When stapes surgery is considered a precise medical history is essential regarding on the start of the hearing impairment. A continuous suspicion will guide to the audiological, radiological and molecular genetic clues to trace the correct diagnosis before embarking on stapes surgery.

Absent semicircular canals in CHARGE syndrome: radiologic spectrum of findings

BACKGROUND AND PURPOSE

This paper describes the CT findings that characterize the middle and inner ear anomalies in coloboma, heart defects, choanal atresia, mental retardation, genitourinary, and ear anomalies (CHARGE) syndrome. With this information, neuroradiologists will be better prepared to provide clinically relevant information to their referring physicians regarding this rare syndrome.

MATERIALS AND METHODS

CT studies from 13 patients were reviewed by 2 neuroradiologists with Certificate of Additional Qualification. Each ear was counted separately for a total of 26 ears. Middle and inner ear anomalies associated with CHARGE syndrome were categorized. Investigational review board approval was obtained.

RESULTS

Twenty of 26 (77%) ears demonstrated cochlear aperture atresia. Four of these ears were evaluated with MR imaging and were found to lack a cochlear nerve. Twenty-one of 26 (81%) cochlea had some form of dysplasia. Six of 26 (23%) round windows were aplastic. Three of 26 (12%) round windows were hypoplastic. Twenty-one of 26 (81%) oval windows were atretic or aplastic. Fifteen of 26 (58%) vestibules were hypoplastic or dysplastic. There were 5 of 26 (19%) enlarged vestibular aqueducts. Twelve of 26 (46%) vestibular aqueducts had an anomalous course. All cases demonstrated absent semicircular canals. Twenty-three of 26 (88%) facial nerve canals had an anomalous course. Four of 26 (15%) tympanic segments were prolapsed. Three of 26 (12%) temporal bones had an anomalous emissary vein referred to as a petrosquamosal sinus. Twenty-one of 26 (81%) middle ear cavities were small. Twenty-three of 26 (93%) ossicles were dysplastic with ankylosis. Three of 26 (12%) internal auditory canals were small.

CONCLUSION

The CT findings that correlate to the anomalies of CHARGE syndrome affect conductive as well as sensorineural hearing. Stenosis of the aperture for the cochlear nerve aperture on CT is suggestive of hypoplasia or absence of the cochlear nerve, which has been demonstrated in some cases by MR. Absence of the cochlear nerve would be a contraindication to cochlear implantation.

Partial absence of the posterior semicircular canal in Alagille syndrome: CT findings

We report a case of bilateral partial absence of the posterior semicircular canals (with normal lateral semicircular canals) imaged with CT in a patient with Alagille syndrome. Similar histologic findings have been reported in the pathology literature. This association has been previously reported only for Waardenburg syndrome in the imaging literature. We review the imaging findings and embryology of the semicircular canals, and suggest that this abnormality is specific to patients with Alagille or Waardenburg syndrome.

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.

Abnormal mesenchymal differentiation in the superior semicircular canal of brn4/pou3f4 knockout mice

OBJECTIVE

To examine the developmental time course of the mutant phenotype and cellular mechanisms that result in malformations of the superior semicircular canal (SSCC) in Brn4 knockout mice. Mutations in the Brn4/Pou3f4 gene result in characteristic inner ear abnormalities in mutant mouse pedigrees, and the findings in these mice are similar to those in human X-linked deafness type III.

DESIGN

Mutant and control mice were killed at various neonatal time points to assess the development of the SSCC. Measurements of SSCC diameter were made on paint-perfused specimens at postnatal day (P) 0, P7, P10, and P14. Histologic evaluation of the SSCC was made on hematoxylin-eosin-stained sections at P10.

RESULTS

A dysmorphic constriction of the superior arc of the SSCC in Brn4 knockout mice was initially detectable at P14. Interestingly, the mutant SSCC is indistinguishable from control mice at earlier neonatal time points. In mutant neonates, there is persistence of immature woven bone with high cellularity surrounding the perilymphatic space of the SSCC. These findings are not present in control animal specimens, which demonstrate appropriate lamellar bony architecture.

CONCLUSIONS

In Brn4 knockout mice, constriction of the SSCC with narrowing of the bony labyrinth develops in the postnatal period at approximately P14. The persistence of immature bone in affected mice indicates that signaling abnormalities disrupt normal mesenchymal differentiation in the SSCC.

Circling behavior in the Ecl mouse is caused by lateral semicircular canal defects

The epistatic circler mouse (Ecl mouse) is a preexisting mutant, which displays a circling phenotype and hyperactivity. It has been shown that the circling phenotype in this mutant results from a complex inheritance pattern, but the vestibular pathology has not been analyzed. The present study deals with the morphological and functional basis responsible for the circling behavior in the Ecl mouse. Morphological examination of the inner ears revealed a bilateral malformation of the horizontal (lateral) semicircular canal and duct. No cochlear abnormalities were detected, and auditory brainstem response (ABR) measurements indicated that the auditory system is not affected. Investigation of the vestibuloocular reflex (VOR) in Ecl mice showed that their horizontal VOR on stimulation is virtually absent, which correlates with the morphological findings.

Molecular Genetic Advances in Semicircular Canal Abnormalities and Sensorineural Hearing Loss: A Report of 16 Cases

OBJECTIVES: The study goals were (1) to determine if the degree and pattern of semicircular canal dysmorphology and the presence or absence of a cochlea in patients with congenital sensorineural hearing loss predict audiologic outcome, severity, or the frequencies involved and (2) to review the recent advances in molecular genetics of the semicircular canals and correlate this information with audiologic and anatomic patterns seen in our series of patients

DESIGN AND SETTING: We conducted a retrospective study at a tertiary care center with a large otologic and cochlear implant service.

PATIENTS AND METHODS: The study population consisted of 16 patients with congenital sensorineural hearing loss in 28 congenitally malformed inner ears consisting of semicircular canal dysplasia or aplasia, with or without cochlear malformation. History, physical examination, computed tomography scans, and serial audiograms were reviewed. Factors analyzed included other phenotypic dysmorphology characteristic of syndromes, audiometric configuration, severity and type of hearing loss, and the presence of associated inner ear anomalies other than the vestibular system. An extensive review of the literature regarding molecular genetic factors in semicircular canal anomalies, with or without cochlear abnormalities, was performed.

RESULTS: Sixteen patients (31 ears) were identified with profound sensorineural hearing loss and semicircular canal abnormalities. Only 3 patients had known syndromes, although 4 patients had other congenital anomalies. Most radiographic detectable abnormalities were bilateral. Audiograms of the patients demonstrated pure tone averages between 90 and 100 dB in the affected ears with few exceptions. No correlation was found between type and severity of malformation of either the cochlea or semicircular canals with the severity of hearing loss. There was no stepwise progression of hearing loss increasing malformation severity. Seven of the 16 patients received cochlear implants. Of these 7, 3 patients had cochlear hypoplasia and 1 patient had a common cavity deformity. Audiologic follow-up on all 7 patients revealed improvement in both speech assessment threshold and pure tone average. Presence or absence of the cochlea was not a factor in outcome after cochlear implantation.

CONCLUSION: We have assembled the largest series of patients with semicircular canal dysmorphology, with or without various cochlear abnormalities. Our study failed to correlate the type and severity of semicircular canal malformation with any specific audiologic outcome. The variation in hearing loss severity and pattern even in patients with similar bony radiographic findings must be explained by other non-radiologically detectable defects, likely abnormalities in membranous labyrinthine development. New molecular genetic discoveries have linked specific genes to the development of certain inner ear structures in mice studies. The independent development of the individual semicircular canals in relation to the cochlea and vestibule and the variability in hearing loss suggest a more complex embryologic process than merely an arrest in development as previously thought. As genetic studies are extended into humans, we will likely be able to stratify these patients by molecular defect and severity of hearing loss. (Otolaryngol Head Neck Surg 2003;129:637-46.)

Congenital aplasia of the semicircular canals

OBJECTIVE

To describe the underrecognized inner ear malformation characterized by complete aplasia of the labyrinthine semicircular canals associated with a relatively well-formed cochlea, to investigate its relationship with known syndromic forms of hearing loss, and to hypothesize regarding the potential embryopathogenesis of this anomaly.

STUDY DESIGN

A retrospective case review consisting of cases of sensorineural hearing loss with radiographic evidence demonstrating agenesis of the semicircular canals associated with a cochlea that was either morphologically normal or sufficiently well developed to accommodate the full insertion of a cochlear implant electrode. Cases were identified by computerized tomography findings that identified the anomaly under study.

SETTING

Departments of otolaryngology and radiology in a tertiary referral center, with a large cochlear implant program serving over 800 patients, more than half of whom are children.

PATIENTS

Fifteen patients with the anomaly under study were identified.

INTERVENTIONS

Each patient underwent a complete otologic examination, audiometric studies, and high resolution computerized tomography of the temporal bone in axial and coronal planes.

MAIN OUTCOME MEASURES

The bony morphology of the cochlea, round and oval windows, vestibule, semicircular canals, and vestibular aqueduct, and the course of the facial nerve were examined. Auditory findings and otologic treatment are presented.

RESULTS

Of the 15 identified patients, 4 were nonsyndromic, 9 had CHARGE association (Coloboma of the eye, congenital Heart defects, choanal Atresia, mental and/or growth Retardation, Genital hypoplasia, and Ear anomalies and/or deafness), 1 met criteria for Noonan's syndrome, and one had features of both these syndromes. Although the cochlea was present in all cases, the cochlear morphology was usually abnormal in the CHARGE association patients. Of the 20 ears in the CHARGE subjects, only 3 ears (15%) were seen to have completely normal development of the cochlea in both the basal and upper turns. The others showed either mild hypoplasia of the upper turns (13 ears, 65%) or an incomplete partition typical of the classic Mondini deformity (4 ears, 20%). In the 4 nonsyndromic cases, one subject had bilateral Mondini dysplasia and the other three had normal cochleae. In the entire group, abnormalities of oval window development were common (20 of 30 ears, 67%), especially in the syndromic cases (18/22, 81%), but the round window was normal in the majority of cases (73%). Seven patients in the CHARGE association group had an anomalous course of the facial nerve, which was particularly severe in three. Four patients had congenital unilateral facial paralysis, although two of these children had normal radiographic anatomy of the facial nerve. One patient had bilateral facial weakness.

CONCLUSIONS

Syndromic and nonsyndromic cases of isolated semicircular canal aplasia were identified. Except for mild to moderate cochlear dysplasia, and the anomalous course of the facial nerve in some CHARGE association patients, both groups of patients were generally suitable for cochlear implantation if indicated. A high incidence of oval window aplasia with normal round window development may help to explain the embryopathogenesis of this anomaly, considering the sequence of inner ear development.

Familial lateral semicircular canal malformation with external and middle ear abnormalities

We report a family with inner ear lateral semicircular canal (LSC) malformation and external and middle ear abnormalities. The family had no history of known syndromes or toxic exposures. Distinct phenotypic manifestations were found in three family members. A young girl exhibited bilateral LSC malformation with a right-sided preauricular tag, a mildly deformed auricle, a stenotic external auditory canal, and a constricted middle ear cavity. She had moderate conductive hearing loss in the right ear but normal hearing in the left ear. Her younger brother exhibited right-sided LSC malformation, microtia, external auditory canal atresia, a malformed middle ear cavity, and abnormal auditory ossicles. He had severe mixed hearing loss in his right ear. Their mother exhibited left-sided LSC malformation without external and middle ear abnormalities, and the hearing was normal in her left ear. None of the three cases had vestibular symptoms, and their results of balance tests were appropriate for the corresponding ages. In contrast, significantly decreased LSC function was revealed by caloric tests in an ear with LSC malformation. Previously, LSC malformation may have been underdiagnosed in patients presenting with external and middle ear abnormalities and their relatives, since this malformation is frequently associated with normal hearing and balance or conductive hearing loss only. To our knowledge, this condition has not been described previously. This condition supports a genetic basis for the combination of LSC malformation and external and middle ear abnormalities and may represent an autosomal dominant condition with variable expressivity.

Cochlear implants in children with craniofacial syndromes: assessment and outcomes

The aim of this retrospective study was to review the outcomes for children with craniofacial syndromes who had received a cochlear implant. The group comprised four children (three girls, one boy) aged between 3.3 and 10.1 years (mean 6.3 years) at time of implantation with the Cochlear CI-22M device. Two children had the CHARGE association. one had Goldenhar's syndrome and one had brachio-oculo-facial syndrome. All had full electrode insertion at time of surgery. At follow-up, three of the children demonstrated benefit in detection, recognition and identification of environmental sounds, and they continued to gain receptive spoken language skills, although none had intelligible speech. The group required careful mapping and higher levels of electrical stimulation of the implant compared to normal child implantees. Stimulation of the facial nerve was a problem with one child. The pre-implantation assessment of these children requires extensive interdisciplinary discussion and careful radiological investigation. Cases should be carefully selected. Parents should receive realistic counselling about outcomes and the time commitment necessary, as habilitation of these children can take twice as long as that of children without additional special needs. Post-implantation, these children continue to require well-coordinated medical and interdisciplinary management.

Dehiscence of the bony roof of the superior semicircular canal in the middle cranial fossa

Spontaneous dehiscence of the superior semicircular canal (SSC) in the middle cranial fossa is rare and may cause clinical problems. This dehiscence was investigated in cadaveric and dried temporal bone specimens. One cadaveric specimen showed a spontaneous defect: the dehiscence was a symmetrical, elongated ellipse with smooth margins. Four of 244 dry bone specimens showed bony defects in the roof of the SSC, however, only one specimen was thought to have a spontaneous defect. Based on computer-simulation models, we hypothesized that spontaneous defects of the SSC may arise during the fetal period. Although rare, this defect may cause problems in middle cranial fossa surgery and may relate to certain vertiginous disorders.

ENU mutagenesis reveals a highly mutable locus on mouse Chromosome 4 that affects ear morphogenesis

Chemical mutagenesis followed by screening for abnormal phenotypes in the mouse holds much promise as a method for revealing gene function. This method is particularly well-suited for discovering genes involved in hearing or balance function, as these defects are relatively easy to screen for in the mouse. We report here the inner ear abnormalities and genetic localization of seven new dominant mutations created by ENU mutagenesis. All seven mutant stocks were identified because of circling and/or head-weaving behavior, which is an indication of balance dysfunction. Investigation of the inner ears of the seven mutant stocks revealed very similar lateral and posterior semicircular canal defects. Studies of the development of the canals in one mutant stock revealed that the affected canals showed reduced outgrowth and delayed canal fusion. Physiological studies performed in one mutant stock showed raised average compound-action-potential thresholds of approximately 10-20 dB sound pressure level (SPL) (depending on frequency), indicating a mild hearing impairment, although scanning electron microscopy performed in several of the mutant stocks revealed no obvious structural defects in the organ of Corti. All seven mutations mapped to the proximal portion of Chromosome (Chr) 4, near the centromere. On the basis of their similar phenotype and map location, we suggest that the seven mutant genes may be allelic and represent a highly mutable locus on Chr 4 that may be particularly susceptible to ENU-induced mutation on the BALB/c genetic background.

The nuclear receptor Nor-1 is essential for proliferation of the semicircular canals of the mouse inner ear

Nor-1 belongs to the nur subfamily of nuclear receptor transcription factors. The precise role of Nor-1 in mammalian development has not been established. However, recent studies indicate a function for this transcription factor in oncogenesis and apoptosis. To examine the spatiotemporal expression pattern of Nor-1 and the developmental and physiological consequences of Nor-1 ablation, Nor-1-null mice were generated by insertion of the lacZ gene into the Nor-1 genomic locus. Disruption of the Nor-1 gene results in inner ear defects and partial bidirectional circling behavior. During early otic development, Nor-1 is expressed exclusively in the semicircular canal forming fusion plates. After formation of the membranous labyrinth, Nor-1 expression in the vestibule is limited to nonsensory epithelial cells localized at the inner edge of the semicircular canals and to the ampullary and utricular walls. In the absence of Nor-1, the vestibular walls fuse together as normal; however, the endolymphatic fluid space in the semicircular canals is diminished and the roof of the ampulla appears flattened due to defective continual proliferative growth of the semicircular canals.

Goldenhar's syndrome: congenital hearing deficit of conductive or sensorineural origin? Temporal bone histopathologic study

BACKGROUND

Oculoauriculovertebral dysplasia (OAVD) (Goldenhar's syndrome) is a congenital syndrome with ipsilateral deformity of the ear and face, epibulbar lipodermoids, coloboma, and vertebral anomalies. Goldenhar's anomaly has often been associated with a degree of congenital hearing deficits, almost always of a conductive origin, but a sensorineural component is also suspected in some cases, evident through malformations of the inner ear.

PATIENTS AND METHODS

Both temporal bones of a 10-day-old deceased patient with oculoauriculovertebral dysplasia were examined by light microscopy.

RESULTS

The ear deformities included deformity of the auricle, atresia of the external auditory canal, and malformation of the tympanic cavity and ossicles. Abnormalities of the stria vascularis and the semicircular canals were also demonstrated. Further inner ear deformities were not identified in this case.

CONCLUSION

These histopathologic findings appear to confirm the conductive component of the congenital hearing deficit, but a sensorineural component could not be omitted. The ear alterations favor early developmental field defects. The causes of this condition are controversial. Recent results in genetic research pertaining to the MSX class genes permit better understanding of the variety, variability, and different degrees of severity of the anomalies described here.

Temporal bone histopathology in trisomy 22

Trisomy 22 has multiple physical anomalies, and aural malformations are commonly associated with trisomy 22. However, there has been only one report describing the temporal bone histopathology in trisomy 22. Our case is the second reported temporal bone histopathology of trisomy 22. Aural anomalies in this case were less serious than those earlier described, though showing Mondini dysplasia of the bony and membranous labyrinth. Deafness in patients with trisomy 22 may manifest sensorineural, conductive or mixed hearing losses, and/or vestibular dysfunction of varying degrees, according to the site and severity of aural anomalies.

Virtual endoscopy of the labyrinth, using a 3D-FastASE sequence

Virtual endoscopy (VE) of the labyrinth was performed using three-dimensional (3D)-fast asymmetric spin-echo MR imaging. The spatial resolution requirements and the usefulness of zero-fill interpolation (ZIP) were evaluated, and VE was used to examine three patients. The (0.6-mm) voxel data with ZIP satisfies the minimum requirements for VE for evaluation of the complex 3D anatomy and pathology of the labyrinth. J. Magn. Reson. Imaging 2001;13:792-796.

Temporal bone anomaly proposed as a major criteria for diagnosis of CHARGE syndrome

The acronym CHARGE defines a non-random clustering of congenital malformations of unknown origin. Classical diagnostic criteria include: 1) one major feature namely coloboma/microphthalmia or choanal atresia, and 2) four of the six features designated in the CHARGE acronym. Interestingly, all CHARGE patients hitherto reported had partial or complete semicircular canal hypoplasia on temporal bone CT-scan. We report on semicircular canal agenesis/hypoplasia in three patients with three to four features of the CHARGE syndrome and neither coloboma nor choanal atresia and we propose to include temporal bone malformations as a major criteria for diagnosis of CHARGE syndrome.

Three-dimensional magnetic resonance imaging findings of inner ear anomaly

Using three-dimensional magnetic resonance imaging (3D-MRI), the membranous labyrinth was examined in normal cases and in a case with bilateral Mondini-type inner ear malformations. Both ears were also examined by high-resolution computed tomography (CT) of the temporal bone. 3D-MRI provided more detail than findings obtained by conventional high-resolution CT and it enabled 3D observations to be made. Detailed examination of maximum intensity projection images along the cochlea axis revealed the cochlear turns in three dimensions.

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.

Unilateral semicircular canal aplasia in Goldenhar's syndrome

A patient with Goldenhar's syndrome (oculoauriculovertebral dysplasia) and unilateral aplasia of all semicircular canals is presented. This is the first report of such a finding and may support the hypothesis that Goldenhar's syndrome and the CHARGE association have a common pathogenetic mechanism.

EphB2 guides axons at the midline and is necessary for normal vestibular function

Mice lacking the EphB2 receptor tyrosine kinase display a cell-autonomous, strain-specific circling behavior that is associated with vestibular phenotypes. In mutant embryos, the contralateral inner ear efferent growth cones exhibit inappropriate pathway selection at the midline, while in mutant adults, the endolymph-filled lumen of the semicircular canals is severely reduced. EphB2 is expressed in the endolymph-producing dark cells in the inner ear epithelium, and these cells show ultrastructural defects in the mutants. A molecular link to fluid regulation is provided by demonstrating that PDZ domain-containing proteins that bind the C termini of EphB2 and B-ephrins can also recognize the cytoplasmic tails of anion exchangers and aquaporins. This suggests EphB2 may regulate ionic homeostasis and endolymph fluid production through macromolecular associations with membrane channels that transport chloride, bicarbonate, and water.

Superior canal dehiscence syndrome

OBJECTIVE

To present the symptoms, signs, and findings on diagnostic tests of patients with the superior canal dehiscence syndrome and to describe the surgical procedures used to treat the dehiscence in five patients.

DESIGN AND SETTING

Prospective study of a series of patients identified as having this syndrome at a tertiary care referral center.

PATIENTS AND RESULTS

Seventeen patients with vertigo, oscillopsia, or both evoked by intense sounds or stimuli that caused changes in middle ear and/or intracranial pressure were identified over a 4-year period. The evoked eye movements had vertical and torsional components, with the direction corresponding to the effect of the stimuli in causing excitation (Valsalva against pinched nostrils, tragal compression, sounds) or inhibition (Valsalva against a closed glottis or jugular venous compression) of the affected superior semicircular canal. Thirteen (76%) of these patients also experienced chronic dysequilibrium that was often the most debilitating symptom. Dehiscence of bone overlying the superior semicircular canal on the affected side was confirmed with computed tomographic scans in each case. Surgical procedures through the middle fossa approach to plug or resurface the superior canal were performed in five patients (canal plugging in three cases and resurfacing of the dehiscence without plugging in two). The debilitating symptoms resolved or improved after the procedures. Signs of vestibular hypofunction, without loss of hearing, were noted in one patient after plugging of the superior canal and in one other patient after resurfacing of the canal.

CONCLUSIONS

The superior canal dehiscence syndrome is identified based on characteristic symptoms, signs, and computed tomographic findings. The clinical presentation and findings can be understood in terms of the effect of the dehiscence on the physiology of the labyrinth. The syndrome is a treatable cause of vestibular disturbance.

Vestibular compensation in infants and children with congenital and acquired vestibular loss in both ears

In children with semicircular canal anomalies, vestibular compensation during their development and growth was studied. The damped rotation test elicited 'absence or poor per-rotatory nystagmus and absence of post-rotatory nystagmus in all cases. Development of gross motor and balance function was seriously delayed in each case during the first 2 or 3 years of life. Thereafter, during the pre-school age, all children could achieve most landmarks of motor development, such as head control, independent walking and running. However, balance functions at the age of entrance of the elementary school (6 years old) were variously impaired in each case. The better case could swim under water but the poor case could not maintain static balance with eyes closed. These motor skills due to vestibular compensation presumably depend on integration of the compensatory input from visual, somatosensory and proprioceptive senses, and the maturation of motor control systems in the cerebellum, basal ganglia and motor cortex.

Targeted mutagenesis of the POU-domain gene Brn4/Pou3f4 causes developmental defects in the inner ear

Targeted mutagenesis in mice demonstrates that the POU-domain gene Brn4/Pou3f4 plays a crucial role in the patterning of the mesenchymal compartment of the inner ear. Brn4 is expressed extensively throughout the condensing mesenchyme of the developing inner ear. Mutant animals displayed behavioral anomalies that resulted from functional deficits in both the auditory and vestibular systems, including vertical head bobbing, changes in gait, and hearing loss. Anatomical analyses of the temporal bone, which is derived in part from the otic mesenchyme, demonstrated several dysplastic features in the mutant animals, including enlargement of the internal auditory meatus. Many phenotypic features of the mutant animals resulted from the reduction or thinning of the bony compartment of the inner ear. Histological analyses demonstrated a hypoplasia of those regions of the cochlea derived from otic mesenchyme, including the spiral limbus, the scala tympani, and strial fibrocytes. Interestingly, we observed a reduction in the coiling of the cochlea, which suggests that Brn-4 plays a role in the epithelial-mesenchymal communication necessary for the cochlear anlage to develop correctly. Finally, the stapes demonstrated several malformations, including changes in the size and morphology of its footplate. Because the stapes anlage does not express the Brn4 gene, stapes malformations suggest that the Brn4 gene also plays a role in mesenchymal-mesenchymal signaling. On the basis of these data, we suggest that Brn-4 enhances the survival of mesodermal cells during the mesenchymal remodeling that forms the mature bony labyrinth and regulates inductive signaling mechanisms in the otic mesenchyme.

Vestibular function in children with the CHARGE association

BACKGROUND

Histopathological examinations and computed tomographic scans of the temporal bone in patients with the CHARGE association (a malformative syndrome that includes coloboma, heart disease, choanal atresia, retarded development, genital hypoplasia, and ear anomalies, including hypoplasia of the external ear and hearing loss) have shown an absence of semicircular canals and a Mondini form of cochlear dysplasia. Until recently, no information was available concerning a possible loss of vestibular function, which could be a factor in retarded posturomotor development. To our knowledge, this is the first report of otolith tests done on patients with the CHARGE association.

OBJECTIVE

To test residual vestibular function in patients with the CHARGE association.

STUDY DESIGN

In 7 patients with the CHARGE association, we made electro-oculographic recordings of vestibulo-ocular responses to earth-vertical and off-vertical axis rotations to evaluate the function of the canal and the otolith-vestibular systems.

RESULTS

None of the 7 patients had semicircular canals in the computed tomographic scan, and none had canal vestibulo-ocular responses to earth-vertical axis rotation, but all had normal otolith vestibulo-ocular responses to the off-vertical axis rotation test.

CONCLUSIONS

These results support the hypothesis of a residual functional otolith organ in the hypoplastic posterior labyrinth of children with the CHARGE association. The severe delays in psychomotor development presented by these children are more likely a consequence of multiple factors: canal vestibular deficit, visual impairment, and environmental conditions (long hospital stays and breathing and feeding problems). The remaining sensitivity of the otolith system to gravity and linear acceleration forces in these children could be exploited in early education programs to improve their posturomotor development.

Nkx5-1 controls semicircular canal formation in the mouse inner ear

The inner ear develops from the otic vesicle, a one-cell-thick epithelium, which eventually transforms into highly complex structures including the sensory organs for balance (vestibulum) and hearing (cochlea). Several mouse inner ear mutations with hearing and balance defects have been described but for most the underlying genes have not been identified, for example, the genes controlling the development of the vestibular organs. Here, we report the inactivation of the homeobox gene, Nkx5-1, by homologous recombination in mice. This gene is expressed in vestibular structures throughout inner ear development. Mice carrying the Nkx5-1 null mutation exhibit behavioural abnormalities that resemble the typical hyperactivity and circling movements of the shaker/waltzer type mutants. The balance defect correlates with severe malformations of the vestibular organ in Nkx5-1(−/−) mutants, which fail to develop the semicircular canals. Nkx5-1 is the first ear-specific molecule identified to play a crucial role in the formation of the mammalian vestibular system.

[Vestibular function: a prerequisite for normal language development?]

BACKGROUND

First language acquisition depends on intermodal perception, especially auditive, tactile-kinesthetic, and partly visual in addition to sensomotoric integration. The influence of the vestibular function for a physiological language development is still unknown.

PATIENT

A case history of a child with bilateral aplasia of all semicircular canals, normacusis in the right ear, and severe sensorineural hearing loss in the left (hearing aid supplied), without mental deficiency, allows us to draw initial conclusions.

RESULTS

Logopedic diagnostics revealed only a mild articulation disorder (interdental sigmatism, inconstant gammacism) as a possible consequence of recurrent middle ear effusions since early childhood. Language development diagnostics did not demonstrate any significant norm deviation.

CONCLUSIONS

In contrast to the statomotoric disorder, no evidence for a specific language impairment was found. Our report elucidates the importance of a selected diagnostic imaging (spiral CT and MIP MRI) in the phoniatric-ped-audiological field.