Radiological prevalence of superior and posterior semicircular canal dehiscence in children

Insights from therapeutic strategies in superior canal dehiscence syndrome: is there anything beyond surgical treatment?

INTRODUCTION

Superior semicircular canal dehiscence syndrome (SCDS) is a clinical syndrome that can cause instability, vertigo, fullness, tinnitus, autophony, hearing loss (HL), Tullio phenomenon, or Hennebert's sign. Historically, surgery has been the primary treatment reported in the literature, although some medical treatments may also be proposed. This study aims to comprehensively characterize SCDS in a large series of patients from clinical, auditory, and vestibular perspectives, and explore medical alternatives to conventional surgical treatments by comparing their results and evolution.

METHODS

A retrospective observational study was designed in a tertiary care center. Audiovestibular tests evaluated included pure-tone audiometry (PTA), VEMPs, video head impulse test (vHIT), and CT imaging. Improvement was assessed over a follow-up period of up to 6 months for seven cardinal symptoms to verify the efficacy of the proposed treatments.

RESULTS

71 subjects with SCDS and a mean age of 51.20 ± 12.22 years were included in the study. The most common symptom found in our sample was instability in 31 patients (43.66%), followed by aural fullness or tinnitus in 29 subjects (40.85%). 36 patients (43.66%) received medical treatment, with 28 of them (77.78%) showing symptom reduction. Surgical repair was indicated in five patients, with all showing symptom improvement. Statistically significant improvement (p < 0.05) was observed, particularly with surgical treatment and acetazolamide, in both symptoms and objective tests such as pure-tone audiometry and VEMPs.

CONCLUSION

SCDS shows significant similarities with other otic capsule dehiscences. It is essential to perform VEMPs and CT scans to complete the diagnosis, which is usually accompanied by clearly recognizable clinical criteria. Surgery for SCDS is effective, safe, and without complications. However, in cases where symptoms are mild to moderate, addressing this condition with medical treatment using diuretics such as acetazolamide has shown promising results.

Audio-Vestibular Evaluation of Pediatric Pseudo-Conductive Hearing Loss: Third Window Syndromes

Conductive hearing loss caused by external or middle ear problems prevents the transmission of sound waves from the external auditory canal to the cochlea, and it is a common condition, especially in pediatric patients aged 1-5 years. The most common etiological factors are otitis media and cerumen during childhood. In some patients, external and middle ear functions and structures may be normal bilaterally despite the air-bone gap on the audiogram. This condition, which is often a missed diagnosis in children, is defined as a pseudo-conductive hearing loss (PCHL) caused by third window syndromes (TWSs) such as semicircular canal dehiscence, inner ear malformations with third window effect, and perilymphatic fistula. In this review of the literature, the authors emphasize the pitfalls of pediatric audio-vestibular evaluation on TWSs as well as the key aspects of this evaluation for the differential diagnosis of PCHL brought on by TWSs. This literature review will provide audiologists and otologists with early diagnostic guidance for TWSs in pediatric patients.

Comparison of Superior Semicircular Canal Bone Thickness and Patterns in Unilateral and Bilateral Cleft Patients and Normal Controls: A CBCT Study

Superior Semicircular Canal Dehiscence (SSCD) is a recently-defined developmental defect may be associated with several craniofacial anomalies such as Cleft Lip/Palate (CLP). The present study aimed to compare subjects with unilateral and bilateral CLP and normal controls in terms of Superior Semicircular Canal (SSC) bone thickness and pattern.

A total of 238 Cone Beam Computed Tomography (CBCT) images were collected from 52 unilateral Cleft Lip and Palate (UCLP) subjects (104 temporal bones) and 38 Bilateral Cleft Lip and Palate (BCLP) (76 temporal bones) subjects and 148 healthy controls (296 temporal bones). The SSC bone thickness was measured twice and validated by a maxillofacial radiologist. The samples were then classified into five categories based on bone thickness: papyraceous or thin, normal, thick, pneumatized, and dehiscence. After all, the UCLP, BCLP, and normal control groups were compared concerning the SSC pattern and thickness.

The results revealed no significant difference among the three groups regarding the SSC pattern and thickness based on gender. The SSC patterns (P value = .001) and SSC thickness (0.01) were strongly correlated to the cleft type. The thinnest bone thickness and the highest incidence of SSCD were observed among the subjects with BCLP.

The results showed a significant association between the SSC patterns and SSC thickness and the study groups.

Otic Capsule Dehiscences Simulating Other Inner Ear Diseases: Characterization, Clinical Profile, and Follow-Up-Is Ménière's Disease the Sole Cause of Vertigo and Fluctuating Hearing Loss?

INTRODUCTION

We present a series of six cases whose clinical presentations exhibited audiovestibular manifestations of a third mobile window mechanism, bearing a reasonable resemblance to Ménière's disease and otosclerosis. The occurrence of these cases in such a short period has prompted a review of the underlying causes of its development. Understanding the pathophysiology of third mobile window syndrome and considering these entities in the differential diagnosis of conditions presenting with vertigo and hearing loss with slight air-bone gaps is essential for comprehending this group of pathologies.

MATERIALS AND METHODS

A descriptive retrospective cohort study of six cases diagnosed at a tertiary center. All of them went through auditive and vestibular examinations before and after a therapeutic strategy was performed.

RESULTS

Out of 84 cases of dehiscences described in our center during the period from 2014 to 2024, 78 belonged to superior semicircular canal dehiscence, while 6 were other otic capsule dehiscences. Among these six patients with a mean age of 47.17 years (range: 18-73), all had some form of otic capsule dehiscence with auditory and/or vestibular repercussions, measured through hearing and vestibular tests, with abnormalities in the results in five out of six patients. Two of them were diagnosed with Ménière's disease (MD). Another two had cochleo-vestibular hydrops without meeting the diagnostic criteria for MD. In two cases, the otic capsule dehiscence diagnosis resulted from an intraoperative complication due to a gusher phenomenon, while in one case, it was an accidental radiological finding. All responded well to the proposed treatment, whether medical or surgical, if needed.

CONCLUSIONS

Otic capsule dehiscences are relatively new and unfamiliar entities that should be considered when faced with cases clinically suggestive of Ménière's disease, with discrepancies in complementary tests or a poor response to treatment. While high-sensitivity and specificity audiovestibular tests exist, completing the study with imaging, especially petrous bone CT scans, is necessary to locate and characterize the otic capsule defect responsible for the clinical presentation.

Posterior Semicircular Canal Dehiscence with Vestibulo-Ocular Reflex Reduction for the Affected Canal at the Video-Head Impulse Test: Considerations to Pathomechanisms

Posterior semicircular canal dehiscence (PSCD) has been demonstrated to result in a third mobile window mechanism (TMWM) in the inner ear similar to superior semicircular canal dehiscence (SSCD). Typical clinical and instrumental features of TMWM, including low-frequency conductive hearing loss (CHL), autophony, pulsatile tinnitus, sound/pressure-induced vertigo and enhanced vestibular-evoked myogenic potentials, have been widely described in cases with PSCD. Nevertheless, video-head impulse test (vHIT) results have been poorly investigated. Here, we present six patients with PSCD presenting with a clinical scenario consistent with a TMWM and an impaired vestibulo-ocular reflex (VOR) for the affected canal on vHIT. In two cases, an additional dehiscence between the facial nerve and the horizontal semicircular canal (HSC) was detected, leading to a concurrent VOR impairment for the HSC. While in SSCD, a VOR gain reduction could be ascribed to a spontaneous "auto-plugging" process due to a dural prolapse into the canal, the same pathomechanism is difficult to conceive in PSCD due to a different anatomical position, making a dural herniation less likely. Alternative putative pathomechanisms are discussed, including an endolymphatic flow dissipation during head impulses as already hypothesized in SSCD. The association of symptoms/signs consistent with TMWM and a reduced VOR gain for the posterior canal might address the diagnosis toward PSCD.

Prevalence of otic capsule dehiscence in temporal bone computed tomography scan

PURPOSE

To investigate the radiologic prevalence of otic capsule dehiscence in temporal bone computed tomography (CT) scan.

METHODS

This was a cross-sectional study. The temporal bone CT scans of the patients presenting to a tertiary center were evaluated for possible dehiscence in any part of the otic capsule; then, all of the dehiscence were confirmed by a trained academic radiologist. For each type of otic capsule dehiscence, at least three planes were used with a specific type of reconstruction. When a dehiscence was present in at least two consecutive images in all planes, it was considered as a true dehiscence.

RESULTS

Six hundred patients (mean age: 40 ± 18.1 years) were enrolled. The prevalence of superior and posterior semicircular canal dehiscence was 6.0% and 2.7%, respectively. The prevalence of cochlear-facial dehiscence, cochlear-internal auditory canal dehiscence, and cochlear-carotid dehiscence was 6.3%, 0.7%, and 0.7%, respectively. The prevalence of vestibular aqueduct-jugular bulb dehiscence was 6.3% and the prevalence of posterior semicircular canal-jugular bulb dehiscence was 0.2%.

CONCLUSIONS

Considering different types of otic capsule dehiscence described, care should be taken in patients with vestibular and auditory signs and symptoms to diagnose these dehiscences.

Predictive Factors for Concurrent Tegmen Dehiscence in Superior Canal Dehiscence Syndrome

OBJECTIVES

To describe factors predictive of tegmen dehiscence in subjects with superior semicircular canal dehiscence syndrome (SCDS).

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary referral center.

PATIENTS

Subjects with SCDS who underwent middle fossa craniotomy (MFC) for plugging/resurfacing.

MAIN OUTCOME MEASURES

Operative and radiographic findings of tegmen dehiscences, preoperative low frequency air-bone gaps (LF-ABGs), ocular vestibular evoked myogenic potential (oVEMP) amplitudes, size of superior semicircular canal dehiscence (SCD), and history of obesity or obstructive sleep apnea (OSA).

RESULTS

One hundred thirty six patients (avg. age, 50.6 yr, 55.1% female) underwent MFC for repair of SCDS. Tegmen dehiscences were commonly found intraoperatively (tegmen tympani dehiscence [TTD] in 19.9% [11% with dural contact of ossicles], tegmen mastoideum dehiscence [TMD] in 28.7%). There were no differences in preoperative LF-ABGs and preoperative oVEMP amplitudes with respect to tegmen status. The sensitivity and specificity of computed tomography (CT) for predicting an intraoperatively confirmed TTD was 85 and 74%, respectively, and 44 and 79% for TMD. History of obesity and OSA did not differ between those with and without tegmen dehiscences. The presence of contralateral SCD and increasing cross-sectional area of SCD were both significantly associated with concurrent tegmen defects.

CONCLUSIONS

Obesity, OSA, preoperative oVEMP, and LF-ABG do not differ between those with SCD alone and those with SCD and concurrent tegmen dehiscences. Likewise, CT scans have relatively low sensitivity for identifying tegmen dehiscences. The presence of concurrent tegmen defects is more common in subjects with larger SCD cross-sectional areas and contralateral SCD.

Relationship Between Superior Semicircular Canal Dehiscence Volume with Clinical Symptoms: Case Series

BACKGROUND

Superior semicircular canal dehiscence (SSCD) is an osseous defect of the arcuate eminence of the petrosal temporal bone. Patients typically present with auditory and vestibular symptoms, such as hearing loss and disequilibrium. Using advanced imaging segmentation techniques, we evaluated whether the volume of SSCD correlated with preoperative symptoms and postoperative outcomes.

METHODS

Our laboratory previously described a novel method of quantifying the size of an SSCD via manual segmentation. High-resolution computed tomography images of the temporal bones were imported into a specialized segmentation software. The volume of the dehiscence was outlined on consecutive slices of the coronal and axial planes via a single-pixel-thick paintbrush tool and was then calculated according to the number of nonzero image voxels.

RESULTS

This study included 111 patients (70 women and 41 men; mean age, 55.1 years; age range, 24-87 years) with a total of 164 SSCDs. Mean postoperative follow-up time was 5.2 months (range, 0.03-59.5 months). The most common preoperative and postoperative symptoms were tinnitus (n = 85) and dizziness (n = 45), respectively. Surgery resulted in improvement of symptoms in most patients. The average volume of 164 SSCDs was 1.3 mm³. SSCD volume was not significantly associated with either preoperative symptoms or postoperative outcomes.

CONCLUSIONS

Advances in imaging techniques have allowed increased visualization of SSCD. Further research will be necessary to evaluate the potential correlation of volume of the dehiscence with clinical variables.

Audiovestibular Quantification in Rare Third Window Disorders in Children

Third window disorders are structural abnormalities in the bony otic capsule that establish a connection between the middle/inner ear or the inner ear/cranial cavity. Investigated extensively in adults, they have hardly been studied in children. This study is a retrospective study of children (aged 5-17 years) diagnosed with rare third window disorders (third window disorders reported rarely or not reported in children) in a tertiary pediatric vestibular unit in the United Kingdom. It aimed to investigate audiovestibular function in these children. Final diagnosis was achieved by high resolution CT scan of the temporal bones. Of 920 children attending for audiovestibular assessment over a 42 month period, rare third windows were observed in 8 (<1%). These included posterior semicircular canal dehiscence (n = 3, 0.3%), posterior semicircular canal thinning (n = 2, 0.2%), X linked gusher (n = 2, 0.2%), and a combination of dilated internal auditory meatus/irregular cochlear partition/deficient facial nerve canal (n = 1, 0.1%). The majority of them (87.5%) demonstrated a mixed/conductive hearing loss with an air-bone gap in the presence of normal tympanometry (100%). Transient otoacoustic emissions were absent with a simultaneous cochlear pathology in 50% of the cohort. Features of disequilibrium were observed in 75% and about a third showed deranged vestibular function tests. Video head impulse test abnormalities were detected in 50% localizing to the side of the lesion. Cervical vestibular evoked myogenic potential test abnormalities were observed in all children in the cohort undergoing the test where low thresholds and high amplitudes classically found in third window disorders localized to the side of the defects in 28.5%. In the series, 71.4% also demonstrated absent responses/amplitude asymmetry, some of which did not localize to the ipsilesional side. Two children presented with typical third window symptoms. This study observes 2 new rare pediatric third window phenotypes and the presence of a cochlear hearing loss in these disorders. It emphasizes that these disorders should be considered as an etiology of hearing loss/disequilibrium in children. It also suggests that pediatric third window disorders may not present with classical third window features and are variable in their presentations/audiovestibular functions.

Children with posterior semicircular canal dehiscence: A case series

Posterior semicircular canal dehiscence is a rare condition and can cause a variety of symptoms. We report three cases of children between 5 and 12 years of age with a PSCD. They all presented with different complaints as follows: Tullio phenomenon in the first case, conductive hearing loss in the second and, conductive hearing loss and pulsatile tinnitus in the third. Imaging showed in all cases a PSCD on the right side, caused by a prominent jugular bulb (high riding bulb). We describe the clinical, audiometric and radiological findings, and discuss the management and therapy. A conservative "wait and see" approach is recommended, especially with children, because of the possible complications of surgery and the possibility that the symptoms will lessen with the skull base osseous maturation.

The variation of superior semicircular canal bone thickness in relation to age and gender

BACKGROUND

Superior semicircular canal dehiscence syndrome (SSCD) is a current diagnosis that is due to a loss of bone covering the superior semicircular canal (SSC). This results in pressure-/sound- induced vertigo and oscillopsia.

OBJECTIVE

To find the variation of the thickness of the bone that covers the Superior Semicircular Canal with relation to age and gender among the Chinese descents.

MATERIALS AND METHODS

Three hundred and eleven temporal bone Cone Beam Computed Tomography (CBCT) images of patients who attended Otology clinic at Second Hospital of Shandong University from January, 2017 to April, 2018 were retrospectively studied. The images were reconstructed in the line of Poschl and the thinnest area of the bone covering the SSC was taken.

RESULTS

We included 172 (55.31%) females and 139 (44.69%) males. Mean age was 41 years. Overall mean difference in thickness was found to be -0.0210. There was no significant difference between the female and male bone thickness (p = .7113). With age the mean difference was 0.0801 (p = .1557) which was not statistically significant.

CONCLUSION AND SIGNIFICANCE

There was no significant change in bone thickness with advancing age. CBCT is the best method of assessing SSCD.

Functional and Objective Audiovestibular Evaluation of Children With Apparent Semicircular Canal Dehiscence-A Case Series in a Pediatric Vestibular Center

Semicircular canal dehiscence is a bony abnormality in the otic capsule especially involving the superior semicircular canal. Since its identification in 1998, there is significant research regarding the pathology in the adult population. This condition generates a third window effect that is well–described in the literature. However, the entity is rare in the pediatric population with limited research. Difficulties encountered in children are obtaining a direct history that is essential for the diagnosis followed by neurovestibular tests that may be difficult to perform. This study presents observations regarding different clinical and diagnostic aspects of semicircular canal dehiscences in children as a retrospective audit in a tertiary pediatric vestibular center. Of 580 children assessed in a 30 months period undergoing comprehensive functional and objective audiovestibular assessment, 13 children (2.2%) were detected to possess radiological semicircular canal dehiscences (high resolution computed tomography scans at 0.625 mm slices reformatted in the axial, coronal and sagittal planes). The right superior semicircular canal was most commonly affected (66.6%). There were 4 bilateral semicircular canal dehiscences. Clinical suspicion of the condition was raised with reliable surrogate history from carers or from older children (100%), a mixed or conductive hearing loss (80% of hearing losses) in the presence of normal impedance audiometry (92.3%), normal transient otoacoustic emissions (84.6%) on the side of the dehiscence and the presence of replicable pathological saccades in the video head impulse test (76.9%). Disequilibrium symptoms and typical third window symptoms were absent or difficult to elicit in children (46.15 and 30.76% respectively). Only 3 (0.5%) fulfilled the adult criteria of a superior semicircular canal dehiscence syndrome. The abnormal video head impulse test characterized by pathological saccades may affect other non-dehisced ipsilateral canals. Semicircular canal dehiscences are rare in children but may be considered as an etiology for hearing losses and imbalance. Children with semicircular canal dehiscence may present differently from the classical superior semicircular canal dehiscence syndrome found in adults.

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.

Recent surgical options for vestibular vertigo

Vertigo is not a well-defined disease but a symptom that can occur in heterogeneous entities diagnosed and treated mainly by otolaryngologists, neurologists, internal medicine, and primary care physicians. Most vertigo syndromes have a good prognosis and management is predominantly conservative, whereas the need for surgical therapy is rare, but for a subset of patients often the only remaining option. In this paper, we describe and discuss different surgical therapy options for hydropic inner ear diseases, Menière's disease, dehiscence syndromes, perilymph fistulas, and benign paroxysmal positional vertigo. At the end, we shortly introduce the most recent developments in regard to vestibular implants. Surgical therapy is still indicated for vestibular disease in selected patients nowadays when conservative options did not reduce symptoms and patients are still suffering. Success depends on the correct diagnosis and choosing among different procedures the ones going along with an adequate patient selection. With regard to the invasiveness and the possible risks due to surgery, in depth individual counseling is absolutely necessary. Ablative and destructive surgical procedures usually achieve a successful vertigo control, but are associated with a high risk for hearing loss. Therefore, residual hearing has to be included in the decision making process for surgical therapy.

Incidence of Pediatric Superior Semicircular Canal Dehiscence and Inner Ear Anomalies: A Large Multicenter Review

OBJECTIVE

To determine the pediatric incidence and association of superior semicircular canal dehiscence (SSCD) with inner ear (IE) anomalies.

STUDY DESIGN

Retrospective chart review.

SETTING

Two tertiary referral centers.

PATIENTS

Children less than 18 years who received a 0.5 mm or less collimated computed tomography study including the temporal bones between 2010 and 2013 for reasons including, but not limited to, hearing loss, trauma, and infection.

INTERVENTIONS

Images were reformatted into Pöschl and Stenver planes. Five hundred three computed tomography studies (1,006 temporal bones) were reviewed by experienced, blinded neuroradiologists.

MAIN OUTCOME MEASURES

Incidence of SSCD and IE anomalies. Patient age, sex, and diagnosis were recorded. Statistical analysis was performed to compare outcome measures among patient demographics.

RESULTS

The incidence of SSCD was 6.2% (31/503) and an IE anomaly was 15.1% (76/503) of individuals. The incidence of SSCD with an IE anomaly was not significantly correlated (1.1%, 40/1,006; p = 0.23; LR = +1.29). The mean age of children with SSCD was lower (5.9 versus 9.8 yr; p = 0.002). SSCD incidence decreased with age (ages <2, 2-8, and 9-18 yr were 36.7%, 5.6%, and 3.2%; p<0.001) and SSC bone thickness nonsignificantly increased with age. Children with SSCD were commonly male (74.2%, p = 0.041).

CONCLUSION

SSCD and IE anomalies are unlikely related. SSCD incidence is highest in children <2 years, with SSC bone increasing until 2 to 8 years of age. This supports the theory of a congenital precedent to SSCD, with overlying bone maturation occurring during early childhood. Age <2 years was a significant predictor of SSCD.

Pediatric superior semicircular canal dehiscence: illustrative case and systematic review

OBJECTIVE The purpose of this study is to present an illustrative case of pediatric superior semicircular canal dehiscence (SSCD) and to systematically review the current published literature in the pediatric population. METHODS An electronic search of the Scopus, Web of Science, PsycINFO, Cochrane, and Embase databases was performed by 2 independent authors through January 2017. Search term combinations included "pediatrics," "children," "canal," and "dehiscence." Inclusion criteria were as follows: English, full-text clinical studies, case reports, and case series describing pediatric patient(s) (younger than 18 years) with CT evidence of SSCD. Baseline patient demographic characteristics, clinical presentations, dehiscence characteristics, management strategies, and outcome data were extracted. RESULTS A total of 14 studies involving 122 patients were included in the quantitative synthesis. The patients' mean age was 7.22 years. Male predominance was observed (approximate male-to-female ratio of 1.65:1). Neurodevelopmental disorders were common (n = 14, 11.5%). Auditory signs and symptoms were more common than vestibular signs and symptoms. Hearing loss (n = 62, 50.8%) was the most common auditory symptom and an indicator for imaging evaluation. Vertigo was the most common vestibular symptom (n = 8, 6.6%). Hearing aids were recommended in 8 cases (6.6%), and surgical repair was performed in 1 case (0.8%). Symptom outcomes and follow-up durations were infrequently reported. CONCLUSIONS The authors' data suggest that in pediatric SSCD, males are more commonly affected than females. This is different than the adult population in which females are predominantly affected. A history of otologic and/or neurodevelopmental abnormalities was common. There was a preponderance of auditory symptoms in this age group. Conservative management was favored in the majority.

Influence of Sex and Age on Posterior Semicircular Canal Thickness

OBJECTIVE

The aim of this study is to determine whether sex and age influence posterior semicircular canal (PSC) thickness.

METHODS

This observational study was conducted in 3 tertiary hospitals. The minimal distance between the PSC and the posterior cranial fossa (PSC thickness) was estimated by thin-section multidetector row computed axial tomography (CAT) scan of the temporal bones. Nonselected consecutive patients of all ages (607 temporal bones) were considered.

RESULTS

A significant effect was only detected for sex (F = 5.418, p = 0.020); PSC thickness showed a higher mean value in women (mean difference ± SE: 0.224 ± 0.096 mm). A significant and negative r value was detected for males aged >45 years (-0.173, p = 0.026); in that group of patients, PSC thickness decreased as age increased (0.018 ± 0.008 mm/year). For females aged ≤45 years, a significant and positive r value was found (0.198, p = 0.022); in that group, PSC thickness increased as age increased (0.020 ± 0.008 mm/year).

CONCLUSIONS

PSC thickness did not significantly evolve with age in young males (≤45 years) but it decreased from age 45 years onwards. On the other hand, PCS thickness increased with age in women until the age of 45 years and it did not significantly change in older females.

[Dehiscence syndromes : Diagnosis and treatment]

BACKGROUND

Dehiscence syndromes of the semicircular canals are a relatively new group of neurotological disorders. They have a variety of symptoms with hearing/balance involvement. Younger patients have clinically relevant symptoms in only about one third of cases. In addition to etiology and pathogenesis, the present paper describes diagnostic and therapeutic possibilities using a patient series of the authors.

MATERIALS AND METHODS

This nonrandomized prospective study included 52 patients with uni-/bilateral dehiscence syndromes of the superior and/or posterior canal (SCDS/PCDS), diagnosed with high-resolution computed tomography (HR-CT) of the petrous bone. Of 41 patients undergoing surgical therapy for severe symptoms-predominantly vertigo attacks (Meniere-like) and/or falls (Tumarkin crises)-31 received single-sided hearing implants.

RESULTS

Of the 41 patients with transmastoid superior and/or posterior canal occlusion, 30 showed a significant improvement of balance in the Dizziness Handicap Inventory (DHI); the dizzy spells ceased. A positive outcome was correlated with the severity of the preoperative disorder; a poor outcome (nonsignificant increase in DHI, recurrent vertigo of various qualities/frequencies) with the comorbidities vestibular migraine, Menière's disease of the contralateral ear, and a dehiscence size exceeding 4 mm.

CONCLUSION

The more severe the vestibular symptoms, the better the outcome of surgical therapy. Auditory symptoms (nonspecific aural fullness, hyperacusis) do not generally respond well to surgical therapy. Cochlear implants have an additional beneficial effect; comorbidities should be considered as (relative) contraindications.

Superior Canal Dehiscence Syndrome: Lessons from the First 20 Years

Superior semicircular canal dehiscence syndrome was first reported by Lloyd Minor and colleagues in 1998. Patients with a dehiscence in the bone overlying the superior semicircular canal experience symptoms of pressure or sound-induced vertigo, bone conduction hyperacusis, and pulsatile tinnitus. The initial series of patients were diagnosed based on common symptoms, a physical examination finding of eye movements in the plane of the superior semicircular canal when ear canal pressure or loud tones were applied to the ear, and high-resolution computed tomography imaging demonstrating a dehiscence in the bone over the superior semicircular canal. Research productivity directed at understanding better methods for diagnosing and treating this condition has substantially increased over the last two decades. We now have a sound understanding of the pathophysiology of third mobile window syndromes, higher resolution imaging protocols, and several sensitive and specific diagnostic tests. Furthermore, we have a treatment (surgical occlusion of the superior semicircular canal) that has demonstrated efficacy. This review will highlight some of the fundamental insights gained in SCDS, propose diagnostic criteria, and discuss future research directions.

Superior semicircular canal dehiscence syndrome

Superior semicircular canal dehiscence (SSCD) syndrome is an increasingly recognized cause of vestibular and/or auditory symptoms in both adults and children. These symptoms are believed to result from the presence of a pathological mobile "third window" into the labyrinth due to deficiency in the osseous shell, leading to inadvertent hydroacoustic transmissions through the cochlea and labyrinth. The most common bony defect of the superior canal is found over the arcuate eminence, with rare cases involving the posteromedial limb of the superior canal associated with the superior petrosal sinus. Operative intervention is indicated for intractable or debilitating symptoms that persist despite conservative management and vestibular sedation. Surgical repair can be accomplished by reconstruction or plugging of the bony defect or reinforcement of the round window through a variety of operative approaches. The authors review the etiology, pathophysiology, presentation, diagnosis, surgical options, and outcomes in the treatment of this entity, with a focus on potential pitfalls that may be encountered during clinical management.

Lateral Skull Base Attenuation in Superior Semicircular Canal Dehiscence and Spontaneous Cerebrospinal Fluid Otorrhea

Objectives

(1) To quantitatively assess the lateral skull base thickness in patients with superior semicircular canal dehiscense (SSCD) using a standardized and validated radiographic measure and to compare it with that of a population with spontaneous cerebrospinal fluid otorrhea (CSFO). (2) To analyze demographic and clinical factors associated with skull base thickness in the SSCD group.

Study Design

Case series with chart review.

Setting

Tertiary neurotologic referral center.

Subjects and Methods

Based on computed tomography imaging of the tegmen, mean skull base thickness was calculated for 16 patients with radiographic and clinical SSCD. Similar measures were performed in 4 comparison groups consisting of adults with spontaneous CSFO (n = 33), as well as 3 control groups recruited from our adult cochlear implant database: 30 obese controls (body mass index [BMI] >30 kg/m2), 11 overweight controls (BMI, 25-30 kg/m2), and 20 normal weight controls (BMI <25 kg/m2).

Results

The SSCD group had a significantly lower mean BMI (28.6 kg/m2) than the spontaneous CSFO group (37.7 kg/m2; P = .0007). The mean skull base thickness of SSCD patients was 17% thinner than that of the CSFO group, 31% thinner vs obese controls, 49% thinner vs overweight controls, and 45% thinner vs normal weight controls. These differences were all statistically significant ( P < .05).

Conclusion

Patients with SSCD have a marked thinning of the lateral skull base, more so than patients with spontaneous CSF otorrhea and control groups with different BMIs. Skull base attenuation in SSCD patients did not correlate with BMI.