Congenital aplasia of the semicircular canals

Embryology, Malformations, and Rare Diseases of the Cochlea

Despite the low overall prevalence of individual rare diseases, cochlear dysfunction leading to hearing loss represents a symptom in a large proportion. The aim of this work was to provide a clear overview of rare cochlear diseases, taking into account the embryonic development of the cochlea and the systematic presentation of the different disorders. Although rapid biotechnological and bioinformatic advances may facilitate the diagnosis of a rare disease, an interdisciplinary exchange is often required to raise the suspicion of a rare disease. It is important to recognize that the phenotype of rare inner ear diseases can vary greatly not only in non-syndromic but also in syndromic hearing disorders. Finally, it becomes clear that the phenotype of the individual rare diseases cannot be determined exclusively by classical genetics even in monogenetic disorders.

Rare Disorders of the Vestibular Labyrinth: of Zebras, Chameleons and Wolves in Sheep's Clothing

The differential diagnosis of vertigo syndromes is a challenging issue, as many - and in particular - rare disorders of the vestibular labyrinth can hide behind the very common symptoms of "vertigo" and "dizziness". The following article presents an overview of those rare disorders of the balance organ that are of special interest for the otorhinolaryngologist dealing with vertigo disorders. For a better orientation, these disorders are categorized as acute (AVS), episodic (EVS) and chronic vestibular syndromes (CVS) according to their clinical presentation. The main focus lies on EVS sorted by their duration and the presence/absence of triggering factors (seconds, no triggers: vestibular paroxysmia, Tumarkin attacks; seconds, sound and pressure induced: "third window" syndromes; seconds to minutes, positional: rare variants and differential diagnoses of benign paroxysmal positional vertigo; hours to days, spontaneous: intralabyrinthine schwannomas, endolymphatic sac tumors, autoimmune disorders of the inner ear). Furthermore, rare causes of AVS (inferior vestibular neuritis, otolith organ specific dysfunction, vascular labyrinthine disorders, acute bilateral vestibulopathy) and CVS (chronic bilateral vestibulopathy) are covered. In each case, special emphasis is laid on the decisive diagnostic test for the identification of the rare disease and "red flags" for potentially dangerous disorders (e. g. labyrinthine infarction/hemorrhage). Thus, this chapter may serve as a clinical companion for the otorhinolaryngologist aiding in the efficient diagnosis and treatment of rare disorders of the vestibular labyrinth.

MRI Evaluation of Vestibular Endolymphatic Space in Patients with Isolated Cystic Lateral Semicircular Canal Malformation

Isolated lateral semicircular canal dysplasia (LSCCD) is one of the most frequent malformations of the bony labyrinth. The aim of this study is to depict morphology and size of the vestibular endolymphatic space in patients with isolated LSCCD using a dedicated 3D high resolution MR sequence called 3D inversion recovery with REAL reconstruction (3D-REAL-IR). From January 2018 to February 2020, we reviewed 281 CT and 241 MR temporal bone studies, and 103 MR studies performed for the evaluation of endolymphatic hydrops (EH). Five patients with LSCCD were found, one of them with bilateral malformation. Three patients (four affected ears) underwent specific MR examination for the evaluation of EH, consisting of a heavily T2-weighed cisternography sequence (T2 SPACE) and a 3D inversion-recovery with REAL reconstruction. The endolymphatic volumetric ratio (ELR) was calculated as the total endolymphatic volume divided by the total lymph (vestibular) volume multiplied by 100. Hydrops MR imaging was available in four of the affected ears. ELR ranged from 22% to 81%. Both extremes were present in the same patient, corresponding to a patient with right unilateral Ménière’s syndrome but with bilateral LSCCD. A patient affected with hearing loss had an ELR of 33% and the last patient with unilateral probable Ménière’s syndrome showed an ELR of 42%. Endolymphatic hydrops imaging is feasible and can be performed on patients with inner ear malformations like LSCCD. The endolymphatic volumetric ratio could be a useful and reproducible tool in daily clinical practice.

Cochlear nerve canal stenosis and associated semicircular canal abnormalities in paediatric sensorineural hearing loss: a single centre study

OBJECTIVE

This study aimed to evaluate the association between cochlear nerve canal dimensions and semicircular canal abnormalities and to determine the distribution of bony labyrinth anomalies in patients with cochlear nerve canal stenosis.

METHOD

This was a retrospective study in which high-resolution computed tomography images of paediatric patients with severe-to-profound sensorineural hearing loss were reviewed. A cochlear nerve canal diameter of 1.5 mm or less in the axial plane was classified as stenotic. Semicircular canals and other bony labyrinth morphology and abnormality were evaluated.

RESULTS

Cochlear nerve canal stenosis was detected in 65 out of 265 ears (24 per cent). Of the 65 ears, 17 ears had abnormal semicircular canals (26 per cent). Significant correlation was demonstrated between cochlear nerve canal stenosis and semicircular canal abnormalities (p < 0.01). Incomplete partition type II was the most common accompanying abnormality of cochlear nerve canal stenosis (15 out of 65, 23 per cent).

CONCLUSION

Cochlear nerve canal stenosis is statistically associated with semicircular canal abnormalities. Whenever a cochlear nerve canal stenosis is present in a patient with sensorineural hearing loss, the semicircular canal should be scrutinised for presence of abnormalities.

Ear malformations: what do radiologists need to know?

Ear malformations represent 50% of ear, nose and throat malformations. Ear malformations cause conductive hearing loss (CHL) and/or sensorineural hearing loss (SNHL) with a significant childhood disability worldwide. Early accurate diagnosis and treatment are mandatory to enhance language and speech development. Understanding the embryology of the ear explains the outcome of ototoxic prenatal insult according to the affected gestational age and the incidence of association among inner, middle, and external ear malformations. Computed tomography (CT) and magnetic resonance imaging (MRI) examinations of the temporal bone are used in the evaluation of ear malformations. In this review article, the spectrum of ear malformations is discussed in detail with hints on the ear embryology, the ear radiological anatomy, and radiological determinant factors of operative reconstruction of ear anomalies.

A New Model for Congenital Vestibular Disorders

Many developmental disorders of the inner ear are manifested clinically as delayed motor development and challenges in maintaining posture and balance, indicating involvement of central vestibular circuits. How the vestibular circuitry is rewired in pediatric cases is poorly understood due to lack of a suitable animal model. Based on this, our lab designed and validated a chick embryo model to study vestibular development in congenital vestibular disorders. The developing inner ear or "otocyst" on the right side of 2-day-old chick embryos (E2) was surgically rotated 180° in the anterior-posterior axis, forming the "anterior-posterior axis rotated otocyst chick" or ARO chick. The ARO chick has a reproducible pathology of a sac with truncated or missing semicircular canals. A sac is the most common inner ear defect found in children with congenital vestibular disorders. In E13 ARO chicks, the sac contained all three cristae and maculae utriculi and sacculi, but the superior crista and macula utriculi were shortened in anterior-posterior extent. Also, the number of principal cells of the tangential vestibular nucleus, a major avian vestibular nucleus, was decreased 66 % on the rotated side. After hatching, no difference was detected between ARO and normal chicks in their righting reflex times. However, unlike normal chicks, ARO hatchlings had a constant, right head tilt, and after performing the righting reflex, ARO chicks stumbled and walked with a widened base. Identifying the structure and function of abnormally developed brain regions in ARO chicks may assist in improving treatments for patients with congenital vestibular disorder.

Bilateral Vestibular Weakness

Bilateral vestibular weakness (BVW) is a rare cause of imbalance. Patients with BVW complain of oscillopsia. In approximately half of the patients with BVW, the cause remains undetermined; in the remainder, the most common etiology by far is gentamicin ototoxicity, followed by much rarer entities such as autoimmune inner ear disease, meningitis, bilateral Ménière’s disease, bilateral vestibular neuritis, and bilateral vestibular schwannomas. While a number of bedside tests may raise the suspicion of BVW, the diagnosis should be confirmed by rotatory chair testing. Treatment of BVW is largely supportive. Medications with the unintended effect of vestibular suppression should be avoided.

Prevalence of Petrosquamosal Sinus and Its Clinical Significance: Radiologic Study and Meta-analysis

OBJECTIVE

The petrosquamosal sinus (PSS) is clinically important as it represents a potential hemorrhagic hazard during neurosurgical procedures. This double-approach radiologic study and meta-analysis aimed to assess the imaging characteristics of the PSS on computed tomography (CT) and systematically analyze its prevalence to improve imaging accuracy and assist in neurosurgical management.

METHODS

The retrospective radiologic study included CT scans of 388 patients aged 18 years or older. All patients with any visible intracranial pathologies or history of head trauma were excluded. To identify articles eligible for inclusion in our meta-analysis, an extensive search was conducted through PubMed, Embase, ScienceDirect, Web of Science, and CNKI. Data extracted included investigative method, prevalence of the PSS among subjects, ethnicity, gender, side, laterality, and mean diameter. The extracted data were pooled into a meta-analysis with a random-effects model.

RESULTS

The radiologic study showed that the PSS was visualized in 25.5% of the sides examined, that it was slightly more common among females (27.5%) than males (23.8%) and on the left (21.7%) than the right (29.4%). Its mean diameter was 1.14 ± 0.58 mm. The meta-analysis revealed that the overall prevalence of the PSS in the population is 11.1%, that it is more common in females (27.4%) than males (17.6%), and that a unilateral PSS is more common (78.2%) than a bilateral one (21.8%).

CONCLUSIONS

As a PSS is present in about one tenth of the population, it is important to consider the possibility that it is present when undertaking neurosurgical procedures and to assess preoperative CT scans to avoid complications.

Cochlear Implantation in Inner Ear Malformations: Systematic Review of Speech Perception Outcomes and Intraoperative Findings

Objective

(1) To analyze reported speech perception outcomes in patients with inner ear malformations who undergo cochlear implantation, (2) to review the surgical complications and findings, and (3) to compare the 2 classification systems of Jackler and Sennaroglu.

Data Sources

PubMed, Scopus (including Embase), Medline, and CINAHL Plus.

Review Methods

Fifty-nine articles were included that contained speech perception and/or intraoperative data. Cases were differentiated depending on whether the Jackler or Sennaroglu malformation classification was used. A meta-analysis of proportions examined incidences of complete insertion, gusher, and facial nerve aberrancy. For speech perception data, weighted means and standard deviations were calculated for all malformations for short-, medium-, and long-term follow-up. Speech tests were grouped into 3 categories—closed-set words, open-set words, and open-set sentences—and then compared through a comparison-of-means t test.

Results

Complete insertion was seen in 81.8% of all inner ear malformations (95% CI: 72.6-89.5); gusher was reported in 39.1% of cases (95% CI: 30.3-48.2); and facial nerve anomalies were encountered in 34.4% (95% CI: 20.1-50.3). Significant improvements in average performance were seen for closed- and open-set tests across all malformation types at 12 months postoperatively.

Conclusions

Cochlear implantation outcomes are favorable for those with inner ear malformations from a surgical and speech outcome standpoint. Accurate classification of anatomic malformations, as well as standardization of postimplantation speech outcomes, is necessary to improve understanding of the impact of implantation in this difficult patient population.

Inner ear malformations: a practical diagnostic approach

Pediatric sensorineural hearing loss is a major cause of disability; although inner ear malformations account for only 20-40% of all cases, recognition and characterization will be vital for the proper management of these patients. In this article relevant anatomy and development of inner ear are surveyed. The role of neuroimaging in pediatric sensorineural hearing loss and cochlear preimplantation study are assessed. The need for a universal system of classification of inner ear malformations with therapeutic and prognostic implications is highlighted. And finally, the radiological findings of each type of malformation are concisely described and depicted. Computed tomography and magnetic resonance imaging play a crucial role in the characterization of inner ear malformations and allow the assessment of the anatomical structures that enable the selection of appropriate treatment and surgical approach.

CT findings of the temporal bone in CHARGE syndrome: aspects of importance in cochlear implant surgery

To provide an overview of anomalies of the temporal bone in CHARGE syndrome relevant to cochlear implantation (CI), anatomical structures of the temporal bone and the respective genotypes were analysed. In this retrospective study, 42 CTs of the temporal bone of 42 patients with CHARGE syndrome were reviewed in consensus by two head-and-neck radiologists and two otological surgeons. Anatomical structures of the temporal bone were evaluated and correlated with genetic data. Abnormalities that might affect CI surgery were seen, such as a vascular structure, a petrosquamosal sinus (13 %), an underdeveloped mastoid (8 %) and an aberrant course of the facial nerve crossing the round window (9 %) and/or the promontory (18 %). The appearance of the inner ear varied widely: in 77 % of patients all semicircular canals were absent and the cochlea varied from normal to hypoplastic. A stenotic cochlear aperture was observed in 37 %. The middle ear was often affected with a stenotic round (14 %) or oval window (71 %). More anomalies were observed in patients with truncating mutations than with non-truncating mutations. Temporal bone findings in CHARGE syndrome vary widely. Vascular variants, aberrant route of the facial nerve, an underdeveloped mastoid, aplasia of the semicircular canals, and stenotic round window may complicate cochlear implantation.

Outcomes of long-term audiological rehabilitation in charge syndrome

The aim of this paper is to assess the long-term audiological features and outcomes of hearing rehabilitation in a large group of individuals with CHARGE Syndrome. The study has been conducted retrospectively, on a paediatric patient database, at the Audiology Department of the University Hospitals of Ferrara and Padua. The study sample included 31 children presenting with different degrees of hearing impairment associated with CHARGE syndrome. Hearing was assessed using auditory brainstem responses (ABRs) and/or electrocochleography, or conditioned audiometry (visual reinforcement audiometry [VRA] or play audiometry). Auditory-perceptual outcomes in terms of communication skills and expressive language were also recorded. The effects of hearing rehabilitation (with hearing aids or cochlear implants) in this group of children and language outcomes after rehabilitation were monitored during long-term follow-up. The outcomes of rehabilitation measures differed in relation to the heterogeneous and often severe disabilities associated with CHARGE syndrome, e.g. developmental delay, intellectual delay, visual impairment, thin 8^th nerve with retrocochlear auditory dysfunction (as described in cases of auditory neuropathy/dyssynchrony). Oral expressive language was severely impaired in most cases, even after lengthy follow-up, suggesting the need for alternative augmentative communication modes. The early identification of sensorineural hearing loss, and carefully planned rehabilitation treatments, can be of some benefit in children with CHARGE syndrome.

Preoperative imaging of sensorineural hearing loss in pediatric candidates for cochlear implantation

Cochlear implantation is the only U.S. Food and Drug Administration-approved treatment for children with marked bilateral sensorineural hearing loss. It provides auditory benefits that range from simple sound detection to substantial word understanding. Improved hearing through cochlear implantation has been demonstrated to enhance the rate of language acquisition, enable development of spoken language, and advance literacy in deaf children. Magnetic resonance imaging and computed tomography both have roles in the preoperative assessment of inner-ear abnormalities, cochlear nerve deficiency, and variant anatomy that may affect the decision to implant and the prognosis for auditory improvement and increase the risk for complications. Most cochlear abnormalities may be successfully treated with cochlear implantation, but the presence of a cochlear malformation may increase the risk for intraoperative cerebrospinal fluid leakage and postoperative bacterial meningitis. Eighth-nerve deficiency correlates with poor auditory outcomes and may affect eligibility for cochlear implantation. Another important consideration for implantation is the presence of labyrinthitis ossificans in some children with deafness resulting from bacterial meningitis, which may cause obstruction that limits electrode insertion. Anatomic variations of the facial nerve or middle-ear cavity, which are more common in syndromic patients, may also affect the surgical approach and make implantation difficult.

Isolated lateral semicircular canal aplasia: Functional consequences

INTRODUCTION

Lateral semicircular canal aplasia is a malformation of the inner ear, usually associated with vestibular and cochlear malformations in the context of congenital malformation syndromes. We report a rare case of a young patient with isolated lateral semicircular canal aplasia and no associated vestibular symptoms.

CLINICAL CASE SUMMARY

A 20-year-old man with no personal or family history presented with persistent unilateral tinnitus for three years with no associated vestibular symptoms. Moderate unilateral right sensorineural hearing loss was detected. Magnetic resonance imaging demonstrated isolated aplasia of the right lateral semicircular canal. Videonystagmography revealed right hyporeflexia. Vestibular evoked myogenic potentials were absent after stimulation on the right side and normal on the left side.

DISCUSSION

Although the morphological abnormalities appeared to be isolated on imaging, the patient presented functional signs of global cochlear, semicircular canal and otolithic lesions, probably related to a developmental disorder of the membranous labyrinth. Functional investigations must be performed in the presence of isolated semicircular canal aplasia, even when it is an incidental finding, to exclude more extensive labyrinthine lesions.

Cochlear Nerve Stimulation in the Internal Auditory Canal in Ossified Cochlea: A Case Study

OBJECTIVE

To present the first reported case of intraneural direct cochlear nerve stimulation in a human being.

STUDY DESIGN

This is a case report.

RESULTS

A 23-year-old patient with bilateral progressive hearing loss associated with bilateral complete semicircular canal aplasia and ossified cochleas underwent cochlear implantation. During surgery, a patent cochlear lumen could not be found, and the array was positioned in the internal auditory canal adjacent to the cochlear nerve. Against our expectations, an assiduous rehabilitation and frequent fitting adjustments have led to a word recognition score, in open set speech with lip reading, of 18/25 and acceptable frequency discrimination.

CONCLUSIONS

We are aware that this was an anomalous use of the cochlear implant, and it is not our aim to suggest a new indication for cochlear array positioning. However, this case shows that auditory perception, to some degree, can be obtained with intraneural direct cochlear nerve stimulation.

CHARGE syndrome and Cochlear implantation: difficulties and outcomes in the paediatric population

OBJECTIVES

CHARGE syndrome is a complex cluster of congenital abnormalities, these children may have absent or hypoplastic auditory nerves. Our objective was to assess preoperative factors and outcomes for paediatric cochlear implant recipients with CHARGE syndrome, to enable better surgical preparation and family counselling.

METHODS

The Sydney Cochlear Implant Centre database was searched for children with CHARGE syndrome who had received a cochlear implant at ages 16 and less. Data were collected regarding clinical history; hearing assessments; MRI and CT scan findings; preoperative transtympanic electrical Auditory Brainstem Response (ABR); intraoperative findings and intraoperative electrical ABR and Neural Response Telemetry; and language outcomes in terms of main language used and Categories of Auditory Performance scores (0-7 ranking).

RESULTS

Ten children were identified. All seven prelingual profoundly deaf children with CHARGE syndrome had hypoplastic or absent auditory nerves bilaterally on MRI scans. Middle ear anatomy was often abnormal, affecting surgical landmarks and making identification of the cochlea very difficult in some cases. Three cases required repeated surgery to obtain successful cochlear implant insertion, one under CT scan image guided technique. All seven children used sign language, or simpler gestures, as their main mode of communication. Two children of of these children, who were implanted early, also attained some spoken language. CAP scores ranged from 0 to 6. The three children with CHARGE syndrome and progressive sensorineural hearing loss had a normal auditory nerve in at least one ear on MRI scans. All had preoperative verbal language, with CAP scores of 6, and continued with CAP scores of 6 following receipt of the cochlear implant.

CONCLUSION

Children with CHARGE and congenital profound hearing loss all had hypoplasia or absent auditory nerves, affecting their outcomes with cochlear implants. They often had markedly abnormal middle ear anatomy and CT image guided surgery can be helpful. These children should be offered a bilingual early intervention approach, using sign language and verbal language, to ensure best language outcomes. Children with CHARGE syndrome and progressive profound hearing loss did well with cochlear implants and continue to be able to use verbal language.

Radiological prevalence of superior and posterior semicircular canal dehiscence in children

OBJECTIVE

Establishing the prevalence of semicircular canal dehiscence in a pediatric population using temporal bone CT imaging.

STUDY DESIGN

Retrospective analysis of all temporal bone CT scans during a 5-year period (2007-2012).

METHODS

CT scan images were reformatted in the plane of the canals and assessed by two independent reviewers with a third to resolve disagreement. Detailed chart review was performed for those found to have dehiscence. Superior and posterior canals were classified as "dehiscent", "possibly dehiscent", "thin" or "normal" for each case.

RESULTS

649 temporal bones were assessed from 334 children (under 18 years of age). The prevalence rate of superior canal dehiscence (SCD) was 1.7% (3.3% of individuals). Posterior canal dehiscence (PCD) was present in 1.2% (2.1% of individuals). There were no cases of bilateral SCD, and one case of bilateral PCD. Age under 3 years was associated with a higher prevalence of thinning but not dehiscence. Congenital inner ear malformation was not related to a higher probability of dehiscence. The superior petrosal sinus was associated with the SCD in three cases (27.3%). Retrospective chart review highlighted possible vestibular symptoms in 3/11 patients with SCD (27.3%).

CONCLUSIONS

This forms the largest pediatric study of canal dehiscence to date. This study's prevalence rate is significantly lower than previous reports. The identified association with overlying venous structures may reflect the etiological process involved. The occurrence in children supports the hypothesis of a congenital predisposition for development of canal dehiscence syndrome.

Auditory brainstem implant candidacy in the United States in children 0-17 years old

OBJECTIVES

The auditory brainstem implant (ABI) is an option for hearing rehabilitation in profoundly deaf patients ineligible for cochlear implantation. Over the past decade, surgeons have begun implanting ABIs in pediatric patients who are unable to receive cochlear implants due to congenital or acquired malformations of the inner ear. No study has examined the potential population-level demand for ABIs in the United States (US). Herein, we aim to quantify the potential need for pediatric ABIs.

METHODS

A systematic literature review was conducted to identify studies detailing the rates of congenital cochlear and/or cochlear nerve (CN) anomalies. Absolute indications for ABI include bilateral cochlea or CN aplasia (Group A), and relative indications for ABI include bilateral cochlea or CN hypoplasia (Group B). Data was subsequently correlated to the US Census Bureau, the National Health Interview Survey, and the Gallaudet Research Institute to provide an estimation of pediatric ABI candidates.

RESULTS

Eleven studies documented rates of bilateral findings. Bilateral cochlea aplasia was identified in 0-8.7% of patients and bilateral CN aplasia in 0-4.8% of patients (Group A). Bilateral cochlea hypoplasia was identified in 0-8.7% of patients and bilateral CN hypoplasia in 0-5.4% of patients (Group B). Using population-level sensorineural hearing loss data, we roughly estimate 2.1% of potential implant candidates meet absolute indications for an ABI in the United States.

CONCLUSION

Congenital cochlear and cochlear nerve anomalies are exceedingly rare. This study provides the first preliminary estimate of cochlea and CN aplasia/hypoplasia at the population level albeit with limitations based on available data. These data suggest the need for dedicated ABI centers to focus expertise and management.

Superior canal dehiscence patients have smaller mastoid volume than age- and sex-matched otosclerosis and temporal bone fracture patients

Background and Objectives

The purpose of the study was to compare the mastoid air-cell volume of the patients with superior semicircular canal dehiscence syndrome (SCDS) and that of the control patients with otosclerosis and temporal bone (TB) fracture.

Subjects and Methods

Ten patients with SCDS were enrolled and 10 patients with bilateral otosclerosis and TB fracture were selected as control groups by age and sex matching. To measure the mastoid air-cell volume, 3D reconstruction software was used.

Results

In 10 patients with SCDS, the mean age was 44.5 years, ranging from 16 to 79 years (M : F=4 : 6). Mean mastoid air-cell volume in the SCDS side was 3319.9 mm³, whereas 4177.2 mm³ in the normal side (p=0.022). Mean mastoid air-cell volume in the right side of otosclerosis patients was 6594.3 mm³ and it was not different from 6380.5 mm³ in the left side (p=0.445). Mean mastoid air-cell volume in normal side of TB fracture was 6477.2 mm³. The mastoid air-cell volume in the SCDS side was significantly smaller than that of otosclerosis and TB fracture patients (p=0.009, p=0.002, respectively). The mastoid air-cell volume in the normal side of SCDS was significantly smaller than that of TB fracture (p=0.019), but not significant with that of otosclerosis (p=0.063).

Conclusions

Our findings revealed that the mastoid air-cell volume in the SCDS side was significantly smaller than control group, which suggest that the decreased mastoid pneumatization is closely related to the generation of SCDS.

Spontaneous tegmen defect and semicircular canal dehiscence: same etiopathogenic entity?

OBJECTIVES

To describe the clinical and radiologic features of associated spontaneous tegmen defects (STDs) with semicircular canal dehiscences (SCCDs) and to postulate a novel etiopathogenic hypothesis of these pathologic conditions.

METHODS

Medical records of all patients with surgically confirmed STD between 2001 and May 2010 were reviewed. We excluded all secondary tegmen defects. Clinical, audiological, and radiologic data were analyzed.

RESULTS

Twenty-three patients matched the inclusion criteria. Semicircular canal dehiscence was associated to STD in 13 patients. Of these patients, 12 (95%) had protruding superior semicircular canals in the middle cranial fossa versus only 3 (30%) of 10 patients for the nondehiscent cases. Twenty-two patients complained of hearing loss. Cerebrospinal fluid leak was found in 13 patients. Four patients had history of meningitis. Vestibular symptoms were present in 8 patients.

CONCLUSION

This is the largest series of reported coexistence of STD and SCCD in the literature. Protrusion of the superior semicircular canal in the middle cranial fossa is probably an additional factor underlying STD and SCCD etiopathogeny. Semicircular canal dehiscence should always be looked for when STD is present.

Role of Chd7 in zebrafish: a model for CHARGE syndrome

CHARGE syndrome is caused by mutations in the CHD7 gene. Several organ systems including the retina, cranial nerves, inner ear and heart are affected in CHARGE syndrome. However, the mechanistic link between mutations in CHD7 and many of the organ systems dysfunction remains elusive. Here, we show that Chd7 is required for the organization of the neural retina in zebrafish. We observe an abnormal expression or a complete absence of molecular markers for the retinal ganglion cells and photoreceptors, indicating that Chd7 regulates the differentiation of retinal cells and plays an essential role in retinal cell development. In addition, zebrafish with reduced Chd7 display an abnormal organization and clustering of cranial motor neurons. We also note a pronounced reduction in the facial branchiomotor neurons and the vagal motor neurons display aberrant positioning. Further, these fish exhibit a severe loss of the facial nerves. Knock-down of Chd7 results in a curvature of the long body axis and these fish develop irregular shaped vertebrae and have a reduction in bone mineralization. Chd7 knockdown also results in a loss of proper segment polarity illustrated by flawed efnb2a and ttna expression, which is associated with later vascular segmentation defects. These critical roles for Chd7 in retinal and vertebral development were previously unrecognized and our results provide new insights into the role of Chd7 during development and in CHARGE syndrome pathogenesis.

The vestibulocochlear nerve: aplasia and hypoplasia in combination with inner ear malformations

OBJECTIVE

To determine features of hypoplasia and aplasia of the vestibulocochlear nerve (VCN) in combination with inner ear malformations (IEMs).

METHODS

Index cases were retrospectively selected from all IEMs collected since 1995. CT and MRI data were reviewed by two neuroradiologists. The number and thickness of visible nerves in the cerebellopontine angle cistern and inside the internal auditory canal (IAC) were analysed.

RESULTS

MR images for 176 patients with IEMs were analysed. Labyrinthine aplasia and otocyst deformity showed 100% correlation, and IAC malformations exhibited 92% correlation with VCN aplasia. Cochlear aplasia, complete aplasia of the semicircular canals, severe cochlear hypoplasia, common cavity, incomplete partition type 1 and mild cochlear hypoplasia showed decreasing degrees of correlation with hypoplasia of the VCN. The remaining types of IEM did not demonstrate VCN hypoplasia.

CONCLUSIONS

Certain forms of IEM show 100% correlation with hypoplasia or aplasia of the VCN, while others correlate less strongly and some do not usually exhibit VCN hypoplasia. MRI should always be carried out for those forms often correlated with VCN hypoplasia.

KEY POINTS

Vestibulocochlear nerve deficiency can be strongly suspected in certain inner ear malformations • Bony cochlear aplasia and cochlear nerve aplasia are strongly correlated • In semicircular canal aplasia, hypoplasia of the vestibular nerve can be found • Before cochlear implantation, the type of any IEM should be fully understood.

Superior semicircular canal dehiscence: congenital or acquired condition?

BACKGROUND AND PURPOSE

It remains unclear whether SSCD syndrome, characterized by onset of vestibular symptoms in the setting of loud noises, is a congenital or acquired condition. The purpose of this investigation was to assess the prevalence of SSCD on imaging among multiple age groups to determine whether this condition is more likely to be congenital or acquired.

MATERIALS AND METHODS

Following approval of the institutional review board, 306 consecutive temporal bone CT examinations performed between July 2005 and March 2007 were retrospectively reviewed. Of these, 2 patients were eliminated due to destructive processes in the inner ear. Patients ranged in age from 7 months to 89 years. Images were independently evaluated by 2 neuroradiologists, and the superior semicircular canal was characterized as normal, thin, or frankly dehiscent in each temporal bone. Any discrepancies were resolved by consensus. The patient list was then subcategorized into 5 age groups, and the prevalence of SSCD was calculated for each group.

RESULTS

Twenty-four patients were identified with SSCD, of which 6 demonstrated dehiscence bilaterally. One hundred thirty-seven subjects were identified with thinning, of which 50 demonstrated thinning bilaterally. Each successively older age category experienced a 93% increase (95% CI, 30%-187%) in the prevalence of SSCD (P = .001) and a 9% increase (95% CI, -5%-25%) in the prevalence of thinning (P = .21). Neither crude nor age-adjusted models demonstrated a significant association between thinning and contralateral dehiscence or vice versa.

CONCLUSIONS

The increased radiologic prevalence of SSCD among older age groups suggests that this is more commonly an acquired rather than congenital condition.

Sensorineural hearing loss: there is no correlation with isolated dysplasia of the lateral semi-circular canal on temporal bone CT

Background

Inner ear malformations may cause sensorineural hearing loss (SNHL). However, the correlation between the small lateral semi-circular canal (LSCC) and SNHL is controversial.

Purpose

To determine whether there is a correlation between the two using CT-based measurement.

Material and Methods

We retrospectively reviewed the high-resolution CT images of the temporal bone obtained from consecutive patients. A total 136 ears of 68 patients (25 men and 43 women; age range 20–85 years, mean 49.8 years) were included in this study. Patients who were clinically suspected to have otosclerosis were also excluded. Two radiologists independently measured the width and cross-sectional area of the bony island of LSCC. We evaluated the correlation between LSCC bone island width or cross-sectional area and hearing level in all cases using Pearson correlation co-efficients. In addition, we compared hearing levels among the patient group with normal-sized LSCC (≧mean-SD), small LSCC (<mean-SD) and very small LSCC (<mean-2SD) as defined by the width and cross-sectional area of the bony island using Student's t-test.

Results

A total 136 ears of 68 patients (25 men and 43 women; age range 20–85 years, mean 49.8 years) were included in this study. No significant correlation was shown between LSCC bony island width or cross-sectional area and hearing level (P > 0.05). No significant difference in hearing levels were found among groups of the normal-sized, small and very small LSCC (P > 0.05).

Conclusion

We conclude that there is no correlation between isolated small LSCC and SNHL.

Posterior semicircular canal dehiscence in asymptomatic ears

CONCLUSIONS

This study revealed that, in the adult population, the final diagnosis of this entity can only be made by combining imaging with clinical tests.

OBJECTIVE

We developed the largest temporal bone multislice computed tomography (CT) scan study so far by including 410 cases to investigate the prevalence of posterior semicircular canal dehiscence in patients with symptoms unrelated to the inner ear.

METHODS

A prospective study was performed in 410 consecutive adult individuals who underwent temporal bone multislice CT scan examinations.

RESULTS

The prevalence of posterior semicircular canal dehiscence was determined to be 1.2%. No superior or lateral semicircular canal defect was detected in these five patients. All cases with posterior semicircular canal defect were male. In two cases the canal was located unilaterally, while in three cases the defects were present bilaterally. Otological examination and audiovestibular tests revealed no abnormal findings in any of the individuals.

Chromodomain proteins in development: lessons from CHARGE syndrome

In humans, heterozygous mutations in the adenosine triphosphate-dependent chromatin remodeling gene CHD7 cause CHARGE syndrome, a common cause of deaf-blindness, balance disorders, congenital heart malformations, and olfactory dysfunction with an estimated incidence of approximately 1 in 10,000 newborns. The clinical features of CHARGE in humans and mice are highly variable and incompletely penetrant, and most mutations appear to result in haploinsufficiency of functional CHD7 protein. Mice with heterozygous loss of function mutations in Chd7 are a good model for CHARGE syndrome, and analyses of mouse mutant phenotypes have begun to clarify a role for CHD7 during development and into adulthood. Chd7 heterozygous mutant mice have postnatal delayed growth, inner ear malformations, anosmia/hyposmia, and craniofacial defects, and Chd7 homozygous mutants are embryonic lethal. A central question in developmental biology is how chromodomain proteins like CHD7 regulate important developmental processes, and whether they directly activate or repress downstream gene transcription or act more globally to alter chromatin structure and/or function. CHD7 is expressed in a wide variety of tissues during development, suggesting that it has tissue-specific and developmental stage-specific roles. Here, we review recent and ongoing analyses of CHD7 function in mouse models and cell-based systems. These studies explore tissue-specific effects of CHD7 deficiency, known CHD7 interacting proteins, and downstream target sites for CHD7 binding. CHD7 is emerging as a critical regulator of important developmental processes in organs affected by human CHARGE syndrome.

Spectrum of hearing disorders and their management in children with CHARGE syndrome

OBJECTIVE

The CHARGE syndrome is associated with ear anomalies and deafness in addition to other malformations. Deformations of the ossicles or aplasia of the semicircular canals, cochlear hypoplasia, hypoplasia or aplasia of the VIIIth cranial nerve and abnormal routing of the VIIth cranial nerve, sigmoid sinus, and emissaries are typical findings. The aim of this study is to explore the feasibility and procedure of cochlear implantation in patients with CHARGE syndrome and to assess the outcome.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center; cochlear implant program.

PATIENTS

Ten patients with CHARGE syndrome and 3 patients with CHARGE-like syndrome treated in our center due to hearing impairment. Eleven patients were congenitally deaf, 1 patient had progressive hearing loss, and 1 patient had mixed hearing loss.

INTERVENTION

Computed tomography of temporal bones and magnetic resonance imaging of the brain; bone-anchored hearing aid surgery, cochlear implantation, rehabilitation results.

MAIN OUTCOME MEASURES

Surgical suitability and hearing rehabilitation.

RESULTS

We illustrate the management of preoperative diagnostics, surgical planning, and hearing rehabilitation. One patient with mixed hearing loss underwent bilateral bone-anchored hearing aid surgery. Because 2 patients had bilateral aplasia of the auditory nerves, we recommended an auditory brainstem implant. The unilateral cochlear implantation was performed in 9 patients and bilateral in 1 patient. In selected cases, it was helpful to plan the operation using a simulator for temporal bone surgery. Complex malformations, such as in CHARGE syndrome, with an increased intraoperative risk for complications should be facilitated by using intraoperative digital volume tomography-assisted navigation and intraoperative digital volume tomography control of electrode position. The results after CI surgery vary due to the differing extent of additional disabilities such as developmental delay, intellectual delay, and visual impairment. Nine of our patients showed improved responsiveness with the cochlear implant. Open speech comprehension could not be observed in 8 patients, whereas the follow-up period was less than 1 year in 4 patients. The relatively high age of our patients at implantation might be an important factor.

CONCLUSION

Careful planning of the treatment of CHARGE syndrome patients with sensorineural hearing loss can, to a limited extent, lead to auditory benefit without increasing surgical complications. Cochlear implantation is therefore indicated after critical assessment.

Semicircular canal dehiscence in the pediatric population

OBJECTIVES

(1) Identify the existence of semicircular canal bony dehiscence in the pediatric population; (2) determine the frequency of this finding in children over 3 years of age who have had temporal bone computed tomography (CT) imaging; (3) correlate the clinical history and audiological data to CT findings in this population.

DESIGN AND SETTING

Retrospective review of temporal bone CT scans performed at a tertiary care children's hospital and retrospective chart review.

PATIENTS

Children over 3 years of age who underwent a temporal bone CT scan between January 2006 and December 2006.

RESULTS

Review of 131 temporal bone CT scans using multiplanar imaging techniques revealed evidence of semicircular canal bony dehiscence in 18 children older than 3 years of age. Dehiscence of the superior semicircular canal was identified in 14 patients while dehiscence of the posterior semicircular canal was identified in 5 patients. One patient had both the superior and posterior semicircular canal dehiscences. Retrospective chart review comparing children with and without semicircular canal dehiscence showed no significant difference in clinical history or audiological data.

CONCLUSIONS

Semicircular canal dehiscence exists in the pediatric population. In this series, 18 of 131 temporal bone CT scans were positive for bony dehiscence of the superior or posterior semicircular canals. Further study is required to determine the clinical significance of this radiographic finding.

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.

Cochlear Implantation in Children With CHARGE Syndrome: Therapeutic Decisions and Outcomes

OBJECTIVES

Ear anomalies and deafness are associated with CHARGE syndrome, which also presents with a cluster of features including coloboma of the eye, heart defects, atresia of the choanae, developmental retardation, and genitourinary abnormalities. The aim of this study is to explore the viability of cochlear implantation in children with CHARGE syndrome and to assess the outcome.

STUDY DESIGN

Retrospective chart review.

METHODS

Eleven children presenting with severe to profound sensorineural hearing loss associated with CHARGE syndrome were the subjects of this study. Routine audiometric measurements and the Infant Toddler Meaningful Auditory Integration Scale (IT-MAIS) were performed pre- and postoperatively. In addition, the degree of the subjects' cochlear deformity were measured and correlated to outcome.

RESULTS

All patients had varying degrees of ear anomalies, seven patients suffered from coloboma of the eyes, two had heart defects, five exhibited choanal atresia, eleven showed developmental retardation, and six had genitourinary abnormalities. Ten of the children underwent cochlear implantation with complete insertion of the electrode array without complication and were followed over a 3-month to a 7-year period. The eleventh child was not implanted because of severe retardation. All of the implanted children showed varying, but limited degrees, of auditory benefit as measured by routine audiometry and the IT-MAIS.

CONCLUSIONS

Careful treatment planning for children with sensorineural hearing loss and CHARGE syndrome can lead to varying, but limited degrees, of auditory benefit with no increase in surgical complications. Although the implant enhanced the children's 'connectivity' to the environment, it did not promote the development of oral language skills in this population.

Loss of Chd7 function in gene-trapped reporter mice is embryonic lethal and associated with severe defects in multiple developing tissues

CHD7 is a novel chromodomain gene mutated in 60%-80% of humans with CHARGE syndrome, a multiple congenital anomaly condition characterized by ocular coloboma, heart defects, atresia of the choanae, retarded growth and development, genital hypoplasia, and characteristic ear abnormalities including deafness. Phenotypic features of CHARGE are highly variable and incompletely penetrant. To explore developmental roles of CHD7, we generated mice carrying the Chd7(Gt) allele from a Chd7-deficient, gene-trapped lacZ reporter ES cell line. RT-PCR of embryo RNA demonstrated significantly reduced levels of wild-type transcript in Chd7(Gt/Gt) embryos. Chd7(Gt/Gt) embryos survive only up to embryonic day 10.5 (E10.5). Chd7(Gt/+) male and female mice are viable, small, and exhibit variable degrees of head-bobbing and circling, consistent with vestibular dysfunction. Paint-filling of E16.5 heterozygous inner ears revealed defects of the semicircular canals. The pattern of beta-galactosidase activity in Chd7(Gt/+) embryos mimics Chd7 mRNA expression in wild-type embryos, confirming the fidelity of the lacZ reporter. We observed tissue-specific beta-galactosidase in the E12.5 and E14.5 Chd7(Gt/+) brain, pituitary, ear, heart, and craniofacial structures, indicating survival of Chd7(Gt/+) cells in CHARGE-relevant organs. These studies demonstrate the utility of Chd7(Gt) as a reporter-tagged loss-of-function allele for future studies exploring developmental mechanisms of Chd7 deficiency.

CHARGE syndrome: an update

CHARGE syndrome is a rare, usually sporadic autosomal dominant disorder due in 2/3 of cases to mutations within the CHD7 gene. The clinical definition has evolved with time. The 3C triad (Coloboma-Choanal atresia-abnormal semicircular Canals), arhinencephaly and rhombencephalic dysfunctions are now considered the most important and constant clues to the diagnosis. We will discuss here recent aspects of the phenotypic delineation of CHARGE syndrome and highlight the role of CHD7 in its pathogeny. We review available data on its molecular pathology as well as cytogenetic and molecular evidences for genetic heterogeneity within CHARGE syndrome.

Inner Ear Dysplasia is Common in Children With Down Syndrome (trisomy 21)

OBJECTIVES/HYPOTHESIS

Middle and external ear anomalies are well recognized in Down syndrome (DS, trisomy 21). Inner ear anomalies are much less frequently described. This study reviews inner ear morphology on imaging to determine the prevalence of cochlear and vestibular anomalies in children with DS.

STUDY DESIGN

The authors conducted a retrospective review of imaging features of (DS) inner ear structures.

METHODS

Fifty-nine sequential patients with DS with imaging of the inner ear were identified by a radiology report text search program. Quantitative biometric assessment of the inner ear was performed on patients with high-resolution computed tomography or magnetic resonance images of the petrous bone. Petrous imaging was performed for evaluation of inflammatory disease or hearing loss. Spinal imaging, which included petrous views, was performed in most cases to exclude C1 to 2 dislocation, a potential complication of DS. Measurements were compared with normative data.

RESULTS

Inner ear dysplasia is much more common in DS than previously reported. Inner ear structures are universally hypoplastic. Vestibular malformations are particularly common and a small bony island of the lateral semicircular canal (<3 mm in diameter) appears highly typical. Additional findings in some patients were persistent lateral semicircular anlage with fusion of the lateral semicircular canal and vestibule into a single cavity, vestibular aqueduct and endolymphatic sac fossa enlargement, cochlear nerve canal hypoplasia, and stenosis or duplication of the internal auditory canal. Stenosis of the external meatus, poor mastoid pneumatization, middle ear and mastoid opacification, and cholesteatoma were common, as expected.

Middle and Inner Ear: Improved Depiction with Multiplanar Reconstruction of Volumetric CT Data

Many anatomic structures of the middle and inner ear are not optimally depicted at computed tomography (CT) with image reconstruction in the standard axial and coronal planes. Recent advances in multidetector CT, including the development of scanners with 32 detector rows, allow the acquisition of isotropic voxels that can be reconstructed in any plane of section. This technique gives radiologists the opportunity to visualize the anatomic structures of the middle and inner ear (the ossicular chain, stapedial footplate-oval window complex, round window, cochlea, vestibular aqueduct, and bones of the superior semicircular canal and facial nerve canal) in greater detail and may help increase the accuracy of CT for the diagnosis of diseases of the middle and inner ear.

Multiple mutations in mouse Chd7 provide models for CHARGE syndrome

Mouse ENU mutagenesis programmes have yielded a series of independent mutations on proximal chromosome 4 leading to dominant head-bobbing and circling behaviour due to truncations of the lateral semicircular canal of the inner ear. Here, we report the identification of mutations in the Chd7 gene in nine of these mutant alleles including six nonsense and three splice site mutations. The human CHD7 gene is known to be involved in CHARGE syndrome, which also shows inner ear malformations and a variety of other features with varying penetrance and appears to be due to frequent de novo mutation. We found widespread expression of Chd7 in early development of the mouse in organs affected in CHARGE syndrome including eye, olfactory epithelium, inner ear and vascular system. Closer inspection of heterozygous mutant mice revealed a range of defects with reduced penetrance, such as cleft palate, choanal atresia, septal defects of the heart, haemorrhages, prenatal death, vulva and clitoral defects and keratoconjunctivitis sicca. Many of these defects mimic the features of CHARGE syndrome. There were no obvious features of the gene that might make it more mutable than other genes. We conclude that the large number of mouse mutants and human de novo mutations may be due to the combination of the Chd7 gene being a large target and the fact that many heterozygous carriers of the mutations are viable individuals with a readily detectable phenotype.

CHARGE syndrome: the phenotypic spectrum of mutations in the CHD7 gene

BACKGROUND

CHARGE syndrome is a non-random clustering of congenital anomalies including coloboma, heart defects, choanal atresia, retarded growth and development, genital hypoplasia, ear anomalies, and deafness. A consistent feature in CHARGE syndrome is semicircular canal hypoplasia resulting in vestibular areflexia. Other commonly associated congenital anomalies are facial nerve palsy, cleft lip/palate, and tracheo-oesophageal fistula. Specific behavioural problems, including autistic-like behaviour, have been described. The CHD7 gene on chromosome 8q12.1 was recently discovered as a major gene involved in the aetiology of this syndrome.

METHODS

The coding regions of CHD7 were screened for mutations in 107 index patients with clinical features suggestive of CHARGE syndrome. Clinical data of the mutation positive patients were sampled to study the phenotypic spectrum of mutations in the CHD7 gene.

RESULTS

Mutations were identified in 69 patients. Here we describe the clinical features of 47 of these patients, including two sib pairs. Most mutations were unique and were scattered throughout the gene. All patients but one fulfilled the current diagnostic criteria for CHARGE syndrome. No genotype-phenotype correlations were apparent in this cohort, which is best demonstrated by the differences in clinical presentation in sib pairs with identical mutations. Somatic mosaicism was detected in the unaffected mother of a sib pair, supporting the existence of germline mosaicism.

CONCLUSIONS

CHD7 mutations account for the majority of the cases with CHARGE syndrome, with a broad clinical variability and without an obvious genotype-phenotype correlation. In one case evidence for germline mosaicism was provided.

Inner Ear Abnormalities in Patients with Goldenhar Syndrome

OBJECTIVE

The objective of this study is to investigate the inner ear malformations in patients with Goldenhar syndrome and to hypothesize the potential embryopathogenesis of these malformations.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Fourteen patients with Goldenhar syndrome.

INTERVENTIONS

Each patient underwent hearing tests and high-resolution computed tomography (CT) of the temporal bone. In six patients, magnetic resonance imaging of the temporal bone also was performed.

RESULTS

Among the 14 patients with Goldenhar syndrome, 13 had outer and middle ear anomalies and 5 (36%) had inner ear malformations, including one case of common cavity.

CONCLUSIONS

Our observations regarding inner ear anomalies in Goldenhar syndrome correlate with the reported cases in the literature and may help to hypothesize the embryological origin of these malformations, which can caused by an early developmental arrest in the fourth gestational week. Specialists evaluating patients with Goldenhar syndrome should be aware of the possibility of inner ear malformations, which could be diagnosed earlier with appropriate imaging studies.

SNP genotyping to screen for a common deletion in CHARGE syndrome

Background

CHARGE syndrome is a complex of birth defects including coloboma, choanal atresia, ear malformations and deafness, cardiac defects, and growth delay. We have previously hypothesized that CHARGE syndrome could be caused by unidentified genomic microdeletion, but no such deletion was detected using short tandem repeat (STR) markers spaced an average of 5 cM apart. Recently, microdeletion at 8q12 locus was reported in two patients with CHARGE, although point mutation in CHD7 on chromosome 8 was the underlying etiology in most of the affected patients.

Methods

We have extended our previous study by employing a much higher density of SNP markers (3258) with an average spacing of approximately 800 kb. These SNP markers are diallelic and, therefore, have much different properties for detection of deletions than STRs.

Results

A global error rate estimate was produced based on Mendelian inconsistency. One marker, rs431722 exceeded the expected frequency of inconsistencies, but no deletion could be demonstrated after retesting the 4 inconsistent pedigrees with local flanking markers or by FISH with the corresponding BAC clone. Expected deletion detection (EDD) was used to assess the coverage of specific intervals over the genome by deriving the probability of detecting a common loss of heterozygosity event over each genomic interval. This analysis estimated the fraction of unobserved deletions, taking into account the allele frequencies at the SNPs, the known marker spacing and sample size.

Conclusions

The results of our genotyping indicate that more than 35% of the genome is included in regions with very low probability of a deletion of at least 2 Mb.

Implante coclear en malformaciones congénitas

OBJECTIVE

The main objective is to evaluate the complications and problems encountered in a population with inner ear congenital malformation undergoing cochlear implantation.

MATERIALS AND METHODS

The present study includes 33 patients with congenital inner ear malformation, from a total population of 346 cochlear implant patients, implanted from February 1993 to March 2004. Radiological evaluation and neurological exams were performed to all these patients in order to evaluate all the preoperative conditions.

RESULTS

The most common cochlear anomalies we found were: cochlear hypoplasia, Incomplete partition and Common cavity (n=15). In 4 cases an enlarge aqueduct was also associated to the cochlear anomaly. We also found 6 cases with labyrinthine anomalies. The surgical procedure was performed in 23 cases, and in 18 of them we obtained an electrical stimulation of the neural elements.

CONCLUSIONS

There are no differences between patients with Incomplete Partition of the cochlea and mild Cochlea hypoplasia, if compared with those with normal cochlea. Severe malformations as Common Cavity or severe hypoplasia may have a higher rate of surgical complications and the outcome cannot be predicted.

Behavior in CHARGE syndrome: Introduction to the special topic

Challenging behavior in children with CHARGE syndrome has been increasingly a concern of parents, educators, and health professionals. This article introduces the special topic in the American Journal of Medical Genetics on behavior in individuals with CHARGE syndrome. It provides background on CHARGE syndrome, diagnostic criteria, and the relationship of sensory and other physical deficits with both development and behavior. Four themes related to our developing understanding of behavior in CHARGE are described: children with CHARGE have behaviors different from those seen in other syndromes with or without deafblindness. The behavior they display is often very adaptive to their environment and to their own disabilities. These behaviors may be partially related to problems with arousal and self-regulation. And, finally, all papers point to behavior as communication, especially within relationships, where it is essential for maximizing intellectual and social outcomes.