Diagnosis Of Superior Semicircular Canal Dehiscence Research Articles

Skull Vibration-Induced Nystagmus in Superior Semicircular Canal Dehiscence: A New Insight into Vestibular Exploration-A Review.

The third window syndrome, often associated with the Tullio phenomenon, is currently most often observed in patients with a superior semicircular-canal dehiscence (SCD) but is not specific to this pathology. Clinical and vestibular tests suggestive of this pathology are not always concomitantly observed and have been recently complemented by the skull-vibration-induced nystagmus test, which constitutes a bone-conducted Tullio phenomenon (BCTP). The aim of this work was to collect from the literature the insights given by this bedside test performed with bone-conducted stimulations in SCD. The PRISMA guidelines were used, and 10 publications were included and analyzed. Skull vibration-induced nystagmus (SVIN), as observed in 55 to 100% of SCD patients, usually signals SCD with greater sensitivity than the air-conducted Tullio phenomenon (ACTP) or the Hennebert sign. The SVIN direction when the test is performed on the vertex location at 100 Hz is most often ipsilaterally beating in 82% of cases for the horizontal and torsional components and down-beating for the vertical component. Vertex stimulations are more efficient than mastoid stimulations at 100 Hz but are equivalent at higher frequencies. SVIN efficiency may depend on stimulus location, order, and duration. In SCD, SVIN frequency sensitivity is extended toward high frequencies, with around 400 Hz being optimal. SVIN direction may depend in 25% on stimulus frequency and in 50% on stimulus location. Mastoid stimulations show frequently diverging results following the side of stimulation. An after-nystagmus observed in 25% of cases can be interpreted in light of recent physiological data showing two modes of activation: (1) cycle-by-cycle phase-locked activation of action potentials in SCC afferents with irregular resting discharge; (2) cupula deflection by fluid streaming caused by the travelling waves of fluid displacement initiated by sound or vibration at the point of the dehiscence. The SVIN direction and intensity may result from these two mechanisms' competition. This instability explains the SVIN variability following stimulus location and frequency observed in some patients but also discrepancies between investigators. SVIN is a recent useful insight among other bedside examination tests for the diagnosis of SCD in clinical practice.

Comparison of digital volume tomography and high-resolution computed tomography in detecting superior semicircular canal dehiscence – a temporal bone study

Conclusion: In detecting a thin bony coverage of a superior semicircular canal (SSC), digital volume tomography (DVT) scans in Poeschl projection seem to be superior to high-resolution computed tomography (CT) scans. Still, a definite diagnosis of SSC dehiscence (SSCD) is not possible with any radiologic imaging technique. Objective: To compare CT and DVT to find out whether DVT is equal, better or worse in showing a thin bony layer on top of an SCC. Methods: In 11 human temporal bone specimens, the SSC was microscopically blue-lined leaving a thin bony coverage on top of it. All specimens were assessed with both high-resolution CT and DVT. After reconstructing the images in Stenvers and Poeschl projections, all images were evaluated by five independent examiners experienced in radiologic imaging of the temporal bone using a four-point ordinal scale, from 1 (distinct dehiscence) to 4 (distinct coverage). Results: The mean score for all CT scans was 2.58 compared with 3.22 for DVT scans (p = 0.000). Poeschl projection showed a mean score of 3.25 compared with 2.55 for Stenvers projection (p = 0.000). The best imaging modality was found to be DVT scans in Poeschl projections, with a mean score of 3.60.

Superior Semicircular Canal Dehiscence in Patients with Spontaneous Cerebrospinal Fluid Otorrhea

To determine the prevalence of superior semicircular canal dehiscence (SCD) in patients with spontaneous cerebrospinal fluid (CSF) otorrhea. Case series with chart review. Tertiary care referral center. Patients included have undergone a middle fossa craniotomy for repair of spontaneous CSF otorrhea between January 2007 and December 2011. The main outcome measure is the presence or absence of SCD observed during spontaneous CSF leak repair. Computed tomography (CT) imaging was also reviewed to determine the diagnostic accuracy of this modality. Thirty-three ears in 31 patients underwent surgical repair for spontaneous CSF otorrhea via a middle fossa craniotomy. The average age at the time of repair was 60.5 years, and 80.6% of patients were female. A dehiscence of the superior canal was observed in 15.2% of ears (16.1% of individuals). No significant difference in age, body mass index, or sex was noted between those patients with or without a superior canal dehiscence. For the diagnosis of SCD, coronal CT was 100% sensitive and 91.7% specific. The positive predictive value and negative predictive value of CT were 66.7% and 100%, respectively. The prevalence of superior semicircular canal dehiscence in ears with spontaneous otorrhea is 15.2%. This prevalence is greater than the 0.5% reported in a temporal bone study of ears not selected for CSF otorrhea.

Anatomo-radiological study of the superior semicircular canal dehiscence of 37 cadaver temporal bones

To assess the presence of dehiscence of the superior semicircular canal (SSCC) on computed tomography (CT) scanning and to study the microscopic anatomo-radiological correlation. Thirty-seven temporal bones preserved in formalin, regardless of the clinical history of cadavers, were studied. A microscopic anatomical study was conducted with an operative microscope (20×). The settings of the CT permitted to obtain 0.6mm slices contiguous reconstruction in Pöschl plane and in Stenvers plane. Three-dimensional (3D) reconstructions were performed if a radiological dehiscence was observed. The apex thickness was measured in Pöschl plane. The radiological positive criterion of SSCC dehiscence was an absence of bone coverage of more than 1mm long in Pöschl and Stenvers planes. We observed three dehiscences of the 37 temporal bones on CT in Pöschl and Stenvers planes. However, no dehiscence was found microscopically. The 3D reconstruction was also positive in these three cases. Reconstructions in the Pöschl plane offered good results up to a bone thickness of 0.6mm. When it was lower than 0.6mm, the interpretation of the images appeared to be subjective. This study emphasizes the limitations of CT imaging, with a risk of false positives to take into account when interpreting the images. The 3D reconstructions also give too many false positives to be used alone and make an accurate diagnosis. The diagnosis of SSCC dehiscence will therefore remain clinical. Complementary and instrumental radiological examinations should be performed only to confirm this clinical suspicion.

CT imaging of superior semicircular canal dehiscence: Added value of reformatted images

Conclusion: Superior semicircular canal dehiscence (SSCD) syndrome may present with various symptoms. CT scans previously interpreted as normal may show SSCD, especially if special reconstructions tailored for superior canal evaluation are added. Objectives: The purpose of this study was to investigate prevalence of SSCD, its length and its correlation with symptoms in patients who had previously undergone temporal bone CT examination that was reported normal and to demonstrate the importance of reformatted images in the diagnosis of SSCD. Methods: We retrospectively reviewed 108 patients who had undergone temporal bone CT examination for various symptoms and were reported as normal. High-resolution temporal bone CT imaging was performed with 1 mm slice thickness in the transverse plane. Each of the superior semicircular canals was evaluated in the plane of Pöschl and Stenver reformatted images together with axial images. Results: Ninety-three patients were included in the study. Nineteen patients with semicircular canal dehiscence were detected. The mean age of the study group was 45 years. Radiologic evidence of SSCD occurred in 23 of 186 temporal bones with a radiologic prevalence of 12%. The most common symptoms in dehiscent patients were vertigo, hearing loss and tinnitus. Defect lengths varied between 1 mm and 6.5 mm.

Déhiscence du canal semi-circulaire antérieur mimant une otospongiose : intérêt de l'imagerie

Objectives To emphasize the role of computerized tomography (CT) in the etiologic work-up of stapes surgery failure. Material and methods Helical high resolution CT scan of the temporal bone with axial and coronal views and multiplanar reconstructions was performed in a patient who had undergone unsuccessful stapedectomy. Results CT scan demonstrated a well located prosthesis, the absence of the radiological hallmarks of otosclerosis, and revealed a superior semicircular canal dehiscence (SSCD). The diagnosis of SSCD was retrospectively considered accountable for the preoperative clinical and audiometric presentation that had mimicked otosclerosis. Conclusion CT is the diagnostic test of choice in elucidating stapes surgery failure (with persistent or recurrent conductive hearing loss), whereas SSCD should be systematically considered among its causes.