Prevalence of Superior Semicircular Canal Dehiscence on High-Resolution CT Imaging in Patients without Vestibular or Auditory Abnormalities

Photon Counting Versus Energy-integrated Detector CT in Detection of Superior Semicircular Canal Dehiscence

BACKGROUND

Superior semicircular canal dehiscence (SSCD), an osseous defect overlying the SSC, is associated with a constellation of audiovestibular symptoms. This study sought to compare conventional energy-integrated detector (EID) computed tomography (CT) to photon-counting detector (PCD)-CT in the detection of SSCD.

MATERIAL AND METHODS

Included patients were prospectively recruited to undergo a temporal bone CT on both EID-CT and PCD-CT scanners. Two blinded neuroradiologists reviewed both sets of images for 1) the presence or absence of SSCD (graded as present, absent, or indeterminate), and 2) the width of the bone overlying the SSC (if present). Any discrepancies in the presence or absence of SSCD were agreed upon by consensus.

RESULTS

In the study 31 patients were evaluated, for a total of 60 individual temporal bones (2 were excluded). Regarding SSCD presence or absence, there was substantial agreement between EID-CT and PCD-CT (k = 0.76; 95% confidence interval, CI 0.54-0.97); however, SSCD was present in only 9 (15.0%) temporal bones on PCD-CT, while EID-CT examinations were interpreted as being positive in 14 (23.3%) temporal bones. This yielded a false positive rate of 8.3% on EID-CT. The bone overlying the SSC was thinner on EID-CT images (0.66 mm; SD = 0.64) than on PCD-CT images (0.72 mm; SD = 0.66) (p < 0.001).

CONCLUSION

The EID-CT examinations tend to overcall the presence of SSCD compared to PCD-CT and also underestimate the thickness of bone overlying the SSC.

Scuba Diving-Induced Inner-Ear Pathology: Imaging Findings of Superior Semicircular Canal and Tegmen Tympani Dehiscence

BACKGROUND Superior semicircular canal dehiscence is an inner-ear pathology which presents with vertigo, disequilibrium, and hearing loss. Although the exact etiology of superior semicircular canal dehiscence is unknown, it is thought that an increase in middle-ear pressure disrupts a thin overlying temporal bone. Superior semicircular canal dehiscence is frequently seen in association with dehiscence of the tegmen tympani, which overlies the middle ear. Here, we present a case report of a 52-year-old Puerto Rican man with vertigo, dizziness, vomiting, and mild hearing loss associated with superior semicircular canal and tegmen tympani dehiscence after performing improper scuba diving techniques. CASE REPORT A 52-year-old Puerto Rican man presented to the emergency department with vertigo, dizziness, vomiting, and mild hearing loss in the right ear. The symptoms began shortly after scuba diving with inadequate decompression techniques on ascent. He was treated with recompression therapy with mild but incomplete improvement in symptoms. Bilateral temporal magnetic resonance imaging was suggestive of segmental dehiscence of the right superior semicircular canal and tegmen tympani. High-resolution computed tomography of the temporal bone confirmed right superior semicircular canal and tegmen tympani dehiscence with an intact left inner ear. CONCLUSIONS The increased inner-ear pressure that occurs during scuba diving can lead to dehiscence of the superior semicircular canal and tegmen tympani, causing vertigo and hearing loss. Performance of improper diving techniques can further increase the risk of dehiscence. Therefore, appropriate radiologic evaluation of the inner ear should be performed in such patients.

Prevalence of Cochlear-Facial and Other Non-Superior Semicircular Canal Third Window Dehiscence on High-Resolution Temporal Bone CT

BACKGROUND AND PURPOSE

The radiologic prevalence of superior semicircular canal dehiscence in the asymptomatic population has been widely studied, but less is known about the rates of other forms of third window dehiscence. Per the existing literature, the radiologic prevalence of cochlear-facial nerve dehiscence, for example, exceeds that seen in histologic studies, suggesting that conventional CT is unreliable for cochlear-facial dehiscence. These studies relied on nonisometric CT acquisitions, however, and underused multiplanar reformatting techniques, leading to false-positive findings. Our purpose was to determine the rate of cochlear-facial dehiscence and other non-superior semicircular canal third window dehiscences on optimized CT in asymptomatic patients.

MATERIALS AND METHODS

Sixty-four-channel temporal bone CT scans from 602 patients in emergency departments were assessed for cochlear-facial and other non-superior semicircular canal third window dehiscences by using high-resolution, multiplanar oblique reformats. Confidence intervals for dehiscence prevalence were calculated using the Newcombe 95% interval confidence method.

RESULTS

Of 602 patients, 500 were asymptomatic, while 102 had an imaging indication consistent with possible third window syndrome (symptomatic). Eight asymptomatic patients (1.6%) had cochlear-facial dehiscence, while 43 (8.4%) had jugular bulb-vestibular aqueduct dehiscence. There was no statistically significant difference between the prevalence of cochlear-facial dehiscence or jugular bulb-vestibular aqueduct dehiscence in asymptomatic patients compared with symptomatic patients. Cochlear-carotid canal, cochlear-internal auditory canal, and cochlear-petrosal sinus dehiscences were not observed.

CONCLUSIONS

Sixty-four-channel CT with multioblique reformatting is sensitive and specific for identifying cochlear-facial dehiscence, with rates similar to those in postmortem series. Jugular bulb-vestibular aqueduct dehiscence is a common incidental finding and is unlikely to produce third window physiology. Other non-superior semicircular canal third window dehiscences are rare in asymptomatic patients.

An evidenced-based diagnostic tool for superior semicircular canal dehiscence syndrome

Purpose

To construct a symptoms-based prediction tool to assess the likelihood of superior canal dehiscence (SSCD) on high-resolution CT.

Materials and methods

Mathematical modeling was employed to predict radiologic evidence of SSCD at a tertiary neurotology referral center.

Results

A total of 168 patients were included, of which 118 had imaging-confirmed SSCD. On univariate analysis significant predictors of SSCD presence were: sound/pressure-induced vertigo (p = 0.006), disequilibrium (p = 0.008), hyperacusis (p = 0.008), and autophony (p = 0.034). Multivariate analysis enabled a 14-point symptom-weighted tool to be developed, wherein a score of ≥6 raised the suspicion of SSCD (≥70% likelihood of being present), R2 = 0.853.

Conclusions

The likelihood of SSCD on CT scan can be determined with a high degree of certainty based on symptoms recorded at presentation. Using the evidenced-based diagnostic tool validated herein, a score ≥6 with any symptom combination justifies ordering a CT scan.

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.

Etiopathology and Prevalence of Pulsatile Tinnitus in a Tertiary Care Referral Hospital

The diverse etiopathogenesis of pulsatile tinnitus (PT) makes it a difficult condition to diagnose and treat. To describe the clinical features, investigations and diagnosis of patients presenting with pulsatile tinnitus (PT). Retrospective chart review in an otology unit of a tertiary care referral centre. All medical records of patients who had a complaint of pulsatile tinnitus during the period 1st January 2014-1st May 2020 were included in the study. Data regarding history, characteristics of tinnitus, examination findings, investigations and diagnosis were collected and analyzed. Sixty-four patients with complaints of PT presented to our clinic during this time period and were included in the study giving a prevalence of 0.09%. Definite diagnosis was made in 62 (96.8%) cases with a detailed history, clinical examination and tailored investigations. Pathologies diagnosed were paraganglioma (25%), superior semicircular canal dehiscence (20.3%), anterior inferior cerebellar artery loop (7.8%), sigmoid sinus wall dehiscence (10.9%), sigmoid sinus diverticulum (6.25%), jugular bulb anomalies (7.8%) and hyperpneumatised petrous apex (3.1%) among others. Rare causes encountered were IgG4 disease, far advanced otosclerosis, vestibular aqueduct dehiscence and idiopathic intracranial hypertension. Pulsatile tinnitus is a rare complaint in the Otology clinic. Almost all cases of PT can be diagnosed correctly and appropriate treatment initiated with a logical approach to investigations.

Case Report: Fremitus Nystagmus in Superior Canal Dehiscence Syndrome

Superior canal dehiscence syndrome (SCDS) is a structural bony defect of the roof of the superior semi-circular canal into the middle cranial fossa and is responsible for the creation of a third window, which alters the dynamics of the inner ear. During humming, vibratory waves entering the vestibulum and cochlea are re-routed through the dehiscence, leading to stimulation of the otolithic and ampullary vestibular organs. This is responsible for the torsional-vertical nystagmus known as “fremitus nystagmus”. In this case report, we video-document a rare case of fremitus nystagmus and its resolution after plugging of the superior semi-circular canal.