Risk of progressive hearing loss in untreated superior semicircular canal dehiscence

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.

Impaired Vestibulo-Ocular Reflex on Video Head Impulse Test in Superior Canal Dehiscence: "Spontaneous Plugging" or Endolymphatic Flow Dissipation?

Surgical plugging of the superior semicircular canal (SSC) represents an effective procedure to treat disabling symptoms in superior canal dehiscence (SCD), despite resulting in an impaired vestibulo-ocular reflex (VOR) gain for the SSC. On the other hand, SSC hypofunction on video head impulse test (vHIT) represents a common finding in patients with SCD exhibiting sound/pressure-induced vertigo, a low-frequency air-bone gap (ABG), and enhanced vestibular-evoked myogenic potentials (VEMPs). "Spontaneous canal plugging" has been assumed as the underlying process. Nevertheless, missing/mitigated symptoms and/or near-normal instrumental findings would be expected. An endolymphatic flow dissipation has been recently proposed as an alternative pathomechanism for SSC VOR gain reduction in SCD. We aimed to shed light on this debate by comparing instrumental findings from 46 ears of 44 patients with SCD exhibiting SSC hypofunction with post-operative data from 10 ears of 10 patients with SCD who underwent surgical plugging. While no difference in SSC VOR gain values was found between the two groups (p = 0.199), operated ears developed a posterior canal hypofunction (p = 0.002). Moreover, both ABG values (p = 0.012) and cervical/ocular VEMP amplitudes (p < 0.001) were significantly higher and VEMP thresholds were significantly lower (p < 0.001) in ears with SCD compared to operated ears. According to our data, canal VOR gain reduction in SCD should be considered as an additional sign of a third window mechanism, likely due to an endolymphatic flow dissipation.

Superior Semicircular Canal Dehiscence Syndrome Following Head Trauma: A Multi-institutional Review

OBJECTIVE

To evaluate patients who become symptomatic from superior semicircular canal dehiscence (SSCD) following head trauma.

STUDY DESIGN

Case series assessing patients presenting with SSCD after a trauma.

METHODS

A case series was completed assessing patients presenting with SSCD after trauma. Data from three academic medical centers were evaluated, including the following: imaging, videonystagmography (VNG)/vestibular evoked myogenic potential (VEMP) testing, audiometric assessment, and surgical repair. Outcome measures included the following: 1) Description of audio-vestibular symptoms, 2) mean pre- and post-operative pure tone average (PTA), word recognition score (WRS), and air bone gap (ABG).

RESULTS

A total of 14 patients were included; 86% were male. Approximately 43% were found to have bilateral SSCD on imaging, with 57% of patients pursuing surgical management. The most common presenting symptoms included pulsatile tinnitus (93%), autophony (79%), and hearing loss (64%). Approximately 36% of patients underwent VNG/VEMP testing, with 83.3% of those demonstrating abnormal results. The mean audiometric findings on the symptomatic side included an air-conduction PTA of 38.0 dB, bone-conduction PTA of 24.3 dB, WRS of 81%, and ABG of 17.9 dB. Among patients who underwent surgery (57%), there was no significant change in the air-conduction PTA, bone-conduction PTA, or WRS (P > .05). However, there was an improvement in the ABG (preoperative = 22.8 dB versus postoperative = 9.7 dB; P = .005).

CONCLUSION

Head trauma may be a potentiating event for SSCD syndrome. This study advances the hypothesis that these patients likely have underlying radiographic SSCD prior to their trauma, and a traumatic event increases in intra-vestibular or intracranial pressures, unmasking SSCD syndrome.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E2810-E2818, 2021.

The Arcuate Eminence and Superior Semicircular Canal: Magnetic Resonance Imaging Study

OBJECTIVE

The present study aimed to explore the relationship between the arcuate eminence (AE) and superior semicircular canal (SSC) using the constructive interference steady-state (CISS) sequence.

PATIENTS AND METHODS

After conventional magnetic resonance imaging, a total of 71 patients underwent the CISS sequence in thin-sliced coronal sections.

RESULTS

In all patients, the SSC was delineated on both sides. In contrast, the AE was identified only in 29 of 71 patients (40.8%) on both sides, varying in shape and relative location to the SSC in the mediolateral dimension. The shortest distance between the highest point of the SSC and middle fossa floor was 1.3 ± 1.1 mm on the right side and 1.3 ± 0.9 mm on the left with considerable variability. A dehiscent SSC with a distance less than 0.2 mm was found in 11.3% of 142 sides. On 22 sides (15.5%), the site on the middle fossa floor, reaching the SSC with the shortest distance (reference point) corresponded to the apex of the AE, equally on the right and left. On 36 sides (25.4%), the distance between the reference point and the apex of the AE was measured as 3.0 ± 1.1 mm on the 18 right sides and 3.7 ± 1.6 mm on the 18 left sides.

CONCLUSIONS

The relationship between AE and SSC is highly variable. Arcuate eminence was not a reliable landmark of the SSC. High-resolution CISS sequence is useful for exploring these structures.

Contribution of Reformatted Multislice Temporal Computed Tomography Images in the Planes of Stenvers and Pöschl to the Diagnosis of Superior Semicircular Canal Dehiscence

OBJECTIVE

In the diagnosis of superior semicircular canal dehiscence (SSCD), computed tomography (CT) is the only imaging method. The aims of the study were to show that reformat images are more accurate than standard planes for diagnosis of SSCD and to determine the prevalence of SSCD.

METHODS

The retrospective review yielded 1309 temporal CTs performed in our radiology department for any reason. Two radiologist interpreted CTs in standard planes collaboratively. Patients with SSCD were reinterpreted in Pöschl and Stenvers planes by 2 radiologists separately.

RESULTS

Statistical analysis was made by accepting that 2 radiologists diagnosis were accurate in Pöschl plane. Coronal plane sensitivity 86%, specificity 64%, Stenvers plane sensitivity 96%, and specificity 52% have been found in the mean result of 2 observers (P < 0.001).

CONCLUSIONS

In the diagnosis of SSCD, standard and Stenvers planes can cause false-negative and false-positive diagnoses. Interpretation in Pöschl plane can significantly increase sensitivity, specificity, negative, and positive predictive values for diagnosing dehiscence.

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.

Three-Category Classification of Magnetic Resonance Hearing Loss Images Based on Deep Autoencoder

Hearing loss, a partial or total inability to hear, is known as hearing impairment. Untreated hearing loss can have a bad effect on normal social communication, and it can cause psychological problems in patients. Therefore, we design a three-category classification system to detect the specific category of hearing loss, which is beneficial to be treated in time for patients. Before the training and test stages, we use the technology of data augmentation to produce a balanced dataset. Then we use deep autoencoder neural network to classify the magnetic resonance brain images. In the stage of deep autoencoder, we use stacked sparse autoencoder to generate visual features, and softmax layer to classify the different brain images into three categories of hearing loss. Our method can obtain good experimental results. The overall accuracy of our method is 99.5%, and the time consuming is 0.078 s per brain image. Our proposed method based on stacked sparse autoencoder works well in classification of hearing loss images. The overall accuracy of our method is 4% higher than the best of state-of-the-art approaches.

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.