Superior Canal Dehiscence Research Articles

Hearing Outcomes for an Underwater Endoscopic Technique for Transmastoid Repair of Superior Semicircular Canal Dehiscence.

To compare hearing outcomes between traditional microsurgical transmastoid repairs and underwater, endoscopic transmastoid repairs of superior semicircular canal dehiscence syndrome (SCDS). A retrospective review of 14 patients undergoing transmastoid repair of SCDS between 2013 and 2017. Preoperative, immediate (7-10 d) postoperative, and long-term (>6 wk) postoperative speech discrimination scores, pure-tone averages, as well as pure-tone air conduction and bone conduction thresholds were obtained at 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, and 8000 Hz. Hearing threshold changes were all calculated as preoperative thresholds subtracted from postoperative threshold at each frequency. Wilcoxon rank-sum tests were conducted to assess changes in postoperative hearing thresholds at both the immediate and long-term postoperative period between those undergoing the traditional transmastoid technique and the underwater, endoscopic transmastoid technique. Our results demonstrate patients who underwent underwater transmastoid repairs had significantly less increase in their high-frequency bone conduction thresholds at both time periods, indicating less sensorineural hearing loss, compared to the traditional microscopic repair (p = 0.02 [effect size, r = 0.4], p = 0.006 [r = 0.6]). At long-term follow-up, there was also significantly improved pure-tone averages in the patients in the underwater repair cohort compared to the traditional group (p = 0.004 [r = 0.6]). There were no differences in air-bone gaps at any frequency or any time period between the two cohorts. Preliminary findings show that the underwater endoscopic technique may prevent sensorineural hearing loss during transmastoid repair of SCDS.

The Supine Superior Semicircular Canal Dehiscence Test.

Purpose The purpose of this clinical focus article is to describe a new method for assessment of superior semicircular canal dehiscence by laying the patient supine during Valsalva-induced nystagmus testing. Method The traditional Valsalva-induced nystagmus test is described, followed by a new method for assessment of superior semicircular dehiscence conducted by laying the patient supine during testing. A case study is presented to illustrate this new testing technique known as the Supine Superior Semicircular Canal Dehiscence Test. Results It is hypothesized that during Valsalva-induced nystagmus testing performed in the upright, seated position, the dura mater could potentially seal the superior semicircular canal fistula, thereby concealing a defect in the bony labyrinth and yielding a false-negative test. To circumvent this, the patient should be placed in the supine position during Valsalva-induced nystagmus testing in order to prevent the dura mater from inadvertently sealing itself against the petrous portion of the temporal bone. The Supine Superior Semicircular Canal Dehiscence Test may reveal the defect in the bony labyrinth and improve the sensitivity of the Valsalva-induced nystagmus test. Conclusions The Supine Superior Semicircular Canal Dehiscence Test may be more sensitive for identifying superior semicircular canal dehiscence in patients with traditional symptoms and a negative Valsalva-induced nystagmus test in the seated position. While a case study is presented to illustrate the potential benefits of including the Supine Superior Semicircular Canal Dehiscence Test in the battery of diagnostic tests, further research is needed in larger samples.

Inflammatory Pseudotumor of the Temporal Bone Leading to Atypical Superior Semicircular Canal Dehiscence Syndrome: A Novel Case Report

Inflammatory pseudotumor of the temporal bone is a benign idiopathic inflammatory process that is rarely encountered in clinical practice. We describe a novel case of a patient who developed superior semicircular canal dehiscence syndrome in the setting of active inflammatory pseudotumor of the temporal bone. One female patient found to have inflammatory pseudotumor of the temporal bone. After treatment with mastoidectomy and steroids, she subsequently developed superior semicircular canal dehiscence syndrome. The patient initially underwent myringotomy and pressure equalization tube placement for a unilateral effusion. Imaging with computed tomography and magnetic resonance imaging revealed a lytic mastoid mass. A complete mastoidectomy was diagnostic for inflammatory pseudotumor and the patient was treated with adjuvant long-term corticosteroids. After this procedure, she was discovered to have new development of symptomatic superior semicircular canal dehiscence syndrome. She eventually underwent a trans-mastoid repair of her superior semicircular canal dehiscence. The patient's clinical course is described with emphasis on the development of superior semicircular canal dehiscence syndrome in the setting of active inflammatory pseudotumor of the temporal bone. The patient's radiographic and clinical history were found to be consistent with inflammatory pseudotumor of the temporal bone. She underwent a therapeutic mastoidectomy with long-term post-operative corticosteroids. During her post-operative course, she developed symptoms of vertigo, hearing loss, and autophony. She was subsequently diagnosed with superior semicircular canal dehiscence and treated with a trans-mastoid repair of the dehiscence. Her symptoms satisfactorily resolved after this surgery. Inflammatory pseudotumor of the temporal bone is a rare benign inflammatory process. We present what is to our knowledge the first description of superior semicircular canal dehiscence syndrome developing in the setting of inflammatory pseudotumor.

Superior Semicircular Canal Dehiscence : Covering Defects in Understanding from Clinical to Radiologic Evaluation.

Superior semicircular canal dehiscence alters the normal fluid mechanics of the vestibulocochlear system and can be adebilitating condition. This article reviews the current understanding of the bony labyrinthine defect, including symptoms, etiology, surgical approach, as well as preoperative and postoperative imaging pearls.

Round Window Reinforcement-Induced Changes in Intracochlear Sound Pressure

Introduction: The round window membrane (RWM) acts as a pressure-relieving membrane for incompressible cochlear fluid. The reinforcement of the RWM has been used as a surgical intervention for the treatment of superior semicircular canal dehiscence and hyperacusis. The aim of this study was to investigate how RWM reinforcement affects sound pressure variations in the cochlea. Methods: The intracochlear sound pressure (ICSP) was simultaneously measured in the scala tympani (ST) and scala vestibuli (SV) of cadaveric human temporal bones (HTBs) in response to acoustic stimulation for three RWM reinforcement materials (soft tissue, cartilage, and medical-grade silicone). Results: The ICSP in the ST was significantly increased after RWM reinforcement for frequencies below 2 kHz. Between 400 and 600 Hz, all three materials demonstrated the highest median pressure increase. The higher the RWM stiffness, the larger the pressure increase: silicone (7 dB) < soft tissue (10 dB) < cartilage (13 dB). The ICSP in the SV was less affected by reinforcement. The highest median pressure increase was 3 dB. The experimental findings can be explained with numerical models of cochlear mechanics. Discussion and conclusions: RWM reinforcement increases the sound pressure in ST at lower frequencies but only has a minor influence on the SV pressure.

Transmastoid Superior Semicircular Canal Plugging: A Prospective Analysis of Surgical Outcomes.

To assess the outcomes of the transmastoid superior semicircular canal plugging in patients with superior semicircular canal dehiscence (SSCD). Prospective cohort study. Tertiary, university center. Patients with SSCD undergoing transmastoid superior semicircular canal plugging within a 30-month period. Transmastoid superior semicircular canal occlusion. We documented the surgical technique, pre- and postoperative (3-month review) dizziness handicap inventory scores, average hearing thresholds, low-frequency air-bone gap, six-canal video head-impulse-test responses, improvement of the auditory symptoms and complications. Out of 30 patients with SSCD, 11 patients (12 ears) were enrolled with an average age 41.17 years (range 32-65 years). Oscillopsia resolved in all patients; DHI score improved from 56.7 (range 22-84) preoperatively to 25.83 (10-46) postoperatively (p = 0.001), while out of the nine patients with troublesome auditory symptoms, five patients noticed an improvement. The average pre- and postoperative hearing thresholds were 15.2 dB (range 3-32.5 dB) and 14.17 dB (range 5-30 dB) (p = 0.73), respectively. The average pre- and postoperative low-frequency air bone gap was 12.3 dB (range 5-20 dB) and 9.4 dB (range 0-20 dB), respectively (p = 0.24) (Table 1). There were no major complications; two patients developed postoperative benign paroxysmal positional vertigo. Transmastoid plugging of the superior semicircular canal can safely and significantly improve the vestibular symptoms of the patients with SCDS, as well as the auditory symptoms in a substantial number of patients in a hearing-preservation way.

Video Head Impulse Test (vHIT) Findings in Patients With Superior Semicircular Canal Dehiscence: A Case-Control Study.

Objective:To explore the usefulness of the responses of video head impulse testing (vHIT) in assessing symptomatic patients with superior semicircular canal dehiscence (SSCD).Methods:This was a prospective case–control study performed in a tertiary skull base referral Centre in the UK. It included all patients ­diagnosed with SSCD from January 2015 to January 2019 and compared to a control group of age and gender-matched unaffected indi­viduals. The main outcome of the study was semicircular canal vestibule-ocular reflex (VOR) gains during vHIT assessment and link to patients’ symptoms.Results:A total of 28 patients were diagnosed with SSCD during the study period and completed the vHIT assessment. Reduced VOR gains (<0.8) were noted in 57% of patients (n = 16). Half of these (n = 8) were in canals other than the superior semicircular (posterior only: n = 5; lateral and posterior: n = 3). Three patients (10.7%) had abnormal responses in 2 canals. The canals in the contralateral side were affected in 56.5% of the cases. There was no correlation with the patients’ symptoms. Results were directly comparable with the control group vHIT results with no identifiable statistically significant differences on comparison of the ipsilateral SSCD side with a randomly selected side from the control group (all comparisons: P > .05).Conclusion:SSCD can affect the vestibular responses from all 3 semicircular canals; not necessarily the superior one. Similar responses were found in a control group of normal subjects. Although the use of vHIT in the assessment of SSCD is not diagnosis-specific, it can still help with identifying the impact of surgery on all canals prior to any intervention in order to avoid bilateral vestibular failure.

Current Trends, Controversies, and Future Directions in the Evaluation and Management of Superior Canal Dehiscence Syndrome.

Patients with superior canal dehiscence syndrome (SCDS) can present with a range of auditory and/or vestibular signs and symptoms that are associated with a bony defect of the superior semicircular canal (SSC). Over the past two decades, advances in diagnostic techniques have raised the awareness of SCDS and treatment approaches have been refined to improve patient outcomes. However, a number of challenges remain. First, there is currently no standardized clinical testing algorithm for quantifying the effects of superior canal dehiscence (SCD). SCDS mimics a number of common otologic disorders and established metrics such as supranormal bone conduction thresholds and vestibular evoked myogenic potential (VEMP) measurements; although useful in certain cases, have diagnostic limitations. Second, while high-resolution computed tomography (CT) is the gold standard for the detection of SCD, a bony defect does not always result in signs and symptoms. Third, even when SCD repair is indicated, there is a lack of consensus about nomenclature to describe the SCD, ideal surgical approach, specific repair techniques, and type of materials used. Finally, there is no established algorithm in evaluation of SCDS patients who fail primary repair and may be candidates for revision surgery. Herein, we will discuss both contemporary and emerging diagnostic approaches for patients with SCDS and highlight challenges and controversies in the management of this unique patient cohort.

Selected Otologic Disorders Causing Dizziness.

This article details updated clinical presentations and current treatment paradigms of the common otologic disorders that may present to the neurologist for vertigo, including Ménière disease, superior semicircular canal dehiscence syndrome, perilymphatic fistula, barotrauma, cholesteatoma, Ramsay Hunt syndrome, enlarged vestibular aqueduct syndrome, and autoimmune inner ear disease including Cogan syndrome. The recent data on modern imaging techniques with three-dimensional delayed IV contrast in Ménière disease, findings on the clinical and testing parameters to diagnose semicircular canal dehiscence and barotrauma, and clinical findings in Ramsay Hunt syndrome, cholesteatoma, and enlarged vestibular aqueduct syndrome are discussed in the article. The most recent findings on the treatment and evaluation of autoimmune inner ear disease and Cogan syndrome are also covered. This article discusses the common clinical otologic entities in patients who may present to the neurologist for vertigo, and it can be used as a guide in the diagnosis of these conditions with the use of auditory, vestibular, and imaging results.

Current trends and applications in endoscopy for otology and neurotology.

There has been a rapid increase in endoscopic ear surgery for the management of middle ear and lateral skull base disease in children and adults over the last decade. In this review paper, we discuss the current trends and applications of the endoscope in the field of otology and neurotology. Advantages of the endoscope include excellent ergonomics, compatibility with pediatric anatomy, and improved access to the middle ear through the external auditory canal. Transcanal endoscopic ear surgery has demonstrated comparable outcomes in the management of cholesteatoma, tympanic membrane perforations, and otosclerosis as compared to microscopic approaches, while utilizing less invasive surgical corridors and reducing the need for postauricular incisions. When a postauricular approach is required, the endoscopic-assisted transmastoid approach can avoid a canal wall down mastoidectomy in cases of cholesteatoma. The endoscope also has utility in treatment of superior canal dehiscence and various skull base lesions including glomus tumors, meningiomas, and vestibular schwannomas. Outside of the operating room, the endoscope can be used during examination of the outer and middle ear and for debridement of complex mastoid cavities. For these reasons, the endoscope is currently poised to transform the field of otology and neurotology.

The Impact of Superior Canal Dehiscence on Power Absorbance, Otoacoustic Emissions, and Hearing in Fat Sand Rats.

Superior Semicircular Canal Dehiscence (SSCD) may lead to vestibular and auditory impairments. To study the effects of power absorbance (PA), Distortion Product Otoacoustic emissions (DPOAE), and hearing thresholds in normal ears of fat sand rats, after a bullotomy, creation and patching. SSCD was performed unilaterally in eight normal hearing animals while the contra-lateral un-operated ear was used as a control. Measures included auditory brain stem responses thresholds for air and bone conduction stimuli, DPOAEs and PA at peak pressure. The normal PA pattern of the animals grossly resembled that of human ears. A bullotomy generated specific, large and significant (p < 0.0001) changes in PA without altering hearing thresholds. SSCD significantly decreased PA at low (p < 0.02) and increased at high frequencies (p < 0.03), but on a smaller scale than the bullotomy. SSCD, induced a mean air-bone gaps of 24.3 for clicks, and 31.2 dB for 1 kHz TB. SSCD also increased the DPOAEs levels by mean of 10.1 dB SPL (p < 0.03). Patching the dehiscence, reversed partially the PA changes, the auditory threshold shifts, and the DPOAEs levels to pre-SSCD values. SSCD affects both incoming and emitting sounds from the ear, probably due to its effect on cochlear impedance and stiffness of the middle and inner ear. The presence of DPOAEs and ABGs indicated a "third window" disease, i.e., SSCD. Due to similar PA patterns after bullotomy and SCCD, PA alone has limited diagnostic yield for patients with SCCD.

Spontaneous Tegmen Tympani Dehiscence: Causes and Treatment of Conductive Hearing Loss.

Conductive hearing loss (CHL) commonly arises in patients with spontaneous dehiscence of the tegmen of the temporal bone with meningoencephalocele (SME). The aim of this study was to further investigate 1) the potential mechanisms for CHL in this setting; 2) hearing outcomes following surgery to address SME, and 3) the possible causes of persistent CHL following surgery. Retrospective case review. Tertiary referral center. Seven patients (six female; nine ears) who underwent middle cranial fossa repair of SME and were found to have a tegmen tympani dehiscence from October 2010 to September 2014 were included in the study. Pre- and postoperative pure-tone audiometry. Eight of nine ears (89%) had audiometric hearing loss at presentation. Seven ears (78%) had an air bone gap of ≥15 dB; all of these had an encephalocele traversing the tegmen tympani defect, four had a middle ear effusion, and three had a simultaneous superior semicircular canal dehiscence (SSCCD). The CHL resolved postoperatively in four of seven ears. Two of the three ears with persistent CHL had SSCCD. Attic ossicular fixation was identified in the other patient and the CHL resolved after ossiculoplasty. CHL associated with SME can be attributed preoperatively to ossicular chain fixation and synchronous SSCCD as well as the more commonly cited cerebrospinal fluid effusion and prolapse of meningoencephalocele onto the ossicular chain. Persistent postoperative CHL can also occur due to SSCCD and ossicular fixation by adhesions.

Reducing Sound Exposure During Ocular Vestibular Evoked Myogenic Potential Testing for Superior Semicircular Canal Dehiscence Syndrome.

Ocular vestibular evoked myogenic potentials (oVEMP) testing in response to air-conducted sound (ACS) has excellent sensitivity and specificity for superior semicircular canal dehiscence syndrome (SCDS). However, patients with SCDS may experience vertigo with the test, and recent works recommend minimizing acoustic energy during VEMP testing. To develop an oVEMP protocol that reduces discomfort and increases safety without compromising reliability. Subjects: Fifteen patients diagnosed with SCDS based on clinical presentation, audiometry, standard VEMP testing, and computed tomography (CT) imaging. There were 17 SCDS-affected ears and 13 unaffected ears. In nine (53%) of the SCDS-affected ears surgical repair was indicated, and SCD was confirmed in each. oVEMPs were recorded in response to ACS using 500 Hz tone bursts or clicks. oVEMP amplitudes evoked by 100 stimuli (standard protocol) were compared with experimental protocols with only 40 or 20 stimuli. In all three protocols, oVEMP amplitudes in SCDS-affected ears were significantly higher than in the unaffected ears (p < 0.001). 500 Hz tone bursts evoked oVEMPs with excellent (>90%) sensitivity and specificity in each of the three protocols. However, in the unaffected ears, lowering to 20 stimuli reduced the detection of oVEMP responses in some ears. Following surgical repair, oVEMPs normalized in each of the protocols. In oVEMP testing using ACS for SCDS, reducing the number of trials from 100 to 40 stimuli results in a more tolerable and theoretically safer test without compromising its effectiveness for the diagnosis of SCDS. Reducing to 20 stimuli may degrade specificity with clicks.

Hearing Outcomes After Surgical Manipulation of the Membranous Labyrinth During Superior Semicircular Canal Dehiscence Plugging or Posterior Semicircular Canal Occlusion.

To analyze audiometric data after surgical manipulation of the membranous labyrinth during plugging of superior semicircular canal dehiscence (SSCD) or posterior semicircular canal occlusion (PSCO) for benign paroxysmal positional vertigo. Retrospective chart review. Tertiary referral center. Patients undergoing plugging of SSCD or PSCO between 2009 and 2019. Pre- and postoperative audiometric data were collected per AAO-HNS guidelines. Hearing outcomes at initial and last follow-up were compared. Subanalyses were performed for surgical approach and age. Eighty-seven total procedures in 76 patients including 43 middle cranial fossa for SSCD, 29 transmastoid SSCD, and 15 PSCO. Mean preoperative air-conduction-pure-tone averages was 21.1±14.9 dB compared with 26.1 ± 19.6 dB at initial follow-up and 24.4 ± 18.6 dB at last follow-up (p = 0.006). Mean preoperative bone-conduction-pure-tone average was 14.3 ± 11.9 dB compared with 18.3 ± 15.6 dB at initial follow-up and 18.5 ± 16.9 dB at last follow-up (p < 0.001). There were five cases of hearing loss >20 dB including one case of profound sensorineural hearing loss >55 dB. PSCO resulted in the most hearing loss at initial follow-up but largely resolves with time. Transmastoid approaches for SSCD resulted in more hearing loss compared with middle cranial fossa. Hearing outcomes were generally stable for SSCD approaches but showed improvement over time for PSCO. Age >50 was associated with greater hearing loss of 5.2 ± 11.1 dB compared with 1.3 ± 10.5 dB but did not reach statistical significance (p = 0.110). Surgical manipulation of the membranous labyrinth results in statistically significant hearing loss in a pooled analysis. Transient hearing loss is observed in PSCO and TM SSCD plugging was associated with postoperative hearing loss. There was a trend toward increased hearing loss in patients >50 years old.

Audiologic Outcomes After Oval and Round Window Reinforcement Surgery.

Oval window (OW) and round window (RW) reinforcement surgery has been used for symptomatic treatment of multiple clinical entities, most commonly perilymphatic fistula and superior semicircular canal dehiscence. Owing to the theoretical acoustically negative effect of stiffening the windows, there has been concern of an unfavorable effect on audiologic outcomes due to the procedure. The purpose of this study is to specifically evaluate audiologic outcomes after OW and RW reinforcement. A retrospective review of patients undergoing transcanal OW or RW reinforcement was completed. Patients were evaluated both as a total group and as two groups separated into "third window" and "two-window" groups based on their specific diagnosis. Primary outcomes included changes in individual pure-tone thresholds, pure-tone average (PTA), air-bone gap, speech reception threshold (SRT), and word recognition scores (WRS) between the preoperative and postoperative groups. Seventy-one patients were included in the study. The combined cohort demonstrated a significant postoperative 2.75 dB increase in the air conduction hearing level at 4000 Hz (p < 0.05). This was almost entirely accounted for by a 2.18 dB increase in the air-bone gap at this frequency (p < 0.05). There were no significant changes in PTA, SRT, or WRS between in the combined group or in the subgroup analysis. OW and RW tissue reinforcement resulted in a statistically significant but likely clinically insignificant decrease in hearing at the 4000 Hz frequency. There was no worsening of PTA, WRS, or SRT.

Video-head impulse test in superior canal dehiscence

Background Superior Canal Dehiscence is classically diagnosed with typical abnormalities on Vestibular Evoked Myogenic Potentials (VEMPs) and Computed Tomography (CT) scans. Aim This paper discusses the utility of the video Head Impulse Test (vHIT) in SCD. Methods Data from 11 ears (8 patients) with SCD were retrospectively reviewed. Results from vHIT, VEMPs and CT and when possible, MRI scans were correlated. An audit of 300 vHIT from patients undergoing routine testing for any neurotological complaint was also conducted to look at the incidence of isolated abnormal superior canal function. Results 82% of patients (9 ears) with SCD showed abnormal vHIT (reduced gain and catch-up saccades) isolated to the affected superior semicircular canal. Conclusion Correlation of the CT and VEMPs are important in forming a diagnosis of SCD. However, if isolated superior canal vHIT abnormalities are demonstrated, it is suggestive of SCD and such patients should be referred for further investigations.

Gray-Scale Inversion on High Resolution Computed Tomography of the Temporal Bone: An Observational Study

This is a qualitative study to explore the utility of gray-scale inversion or the "invert" function of high-resolution computed tomography (HRCT) scans in the diagnosis of temporal bone anatomy and pathology. This is a case series describing an innovative application of an existing image processing tool to visualize temporal bone anatomy and pathology. Illustrative patients at a tertiary referral center with otologic symptoms and findings leading to HRCT scans of the temporal bone were included. Diagnostic HRCT scans were evaluated utilizing the gray-scale inversion function (invert function). Nine illustrative cases which demonstrate conditions such as persistent stapedial artery, membranous stapes footplate, total ossicular prosthesis migration into the vestibule, third window syndrome such as superior semicircular canal dehiscence (SSCD) and cochlea-facial nerve dehiscence, otosclerosis, and ossicular chain discontinuity are included. The enhanced visualization was confirmed surgically in 3 cases, and 1 had physiological confirmation using cervical vestibular evoked myogenic potentials (cVEMP). Gray-scale inversion can be used to improve visualization of temporal bone anatomy and pathologic changes when diagnoses are in doubt. The invert function is a useful adjunct in the armamentarium of both radiologists and otologists when evaluating HRCT of the temporal bone.

Optimized Diagnostic Approach to Patients Suspected of Superior Semicircular Canal Dehiscence.

Current methods of diagnosing superior semicircular canal dehiscence syndrome (SCDS) include a clinical exam, audiometric testing, temporal bone computer tomography (CT) imaging, and vestibular evoked myogenic potential (VEMP) testing. The main objective of this study was to develop an improved diagnostic approach to SCDS optimized for accuracy, efficiency, and safety that utilizes clinical presentation, audiometric testing, CT imaging, high-frequency cervical VEMP (cVEMP) testing, and patient treatment preference. A secondary aim was to investigate the cost associated with the current versus proposed diagnostic paradigms. All patients who underwent cVEMP testing since introduction of the 2 kHz cVEMP in our clinical protocol in July 2018 were screened. Patients suspected of SCDS based upon symptoms who also had available audiogram, CT scan, and 2 kHz cVEMP were included (58 ears). Patients were categorized as dehiscent, thin, or not dehiscent based on their CT scan. Symptom prevalence and cVEMP outcomes were analyzed and compared for all groups. The accuracy of the 2 kHz cVEMP was calculated using CT imaging as the standard. Using a combination of patient symptomatology, audiometric, CT and 2 kHz cVEMP data, as well as patient preference, a best clinical practice approach was developed. The cost associated with this approach was calculated and compared with cost of the current SCDS diagnostic workup using Medicare reimbursement rates. In the overall patient population suspected of SCDS based on clinical presentation, the sensitivity and specificity of 2 kHz cVEMP were 76% and 100%, respectively, while the positive and negative predictive values were 100% and 84.6%, assuming that the CT scan finding was correct. Autophony was the most common symptom in patients who had both superior semicircular canal dehiscence on CT imaging plus abnormal 2 kHz cVEMP (p < 0.001). Combining patient symptomatology, 2 kHz normalized peak to peak cVEMP amplitude, and patient treatment preference to determine, which patients should undergo CT scanning resulted in a potential cost reduction between 45% and 61%. In patients suspected of SCDS based on their clinical presentation, the combination of symptomatology, 2 kHz cVEMP data, and patient preference can be used to determine which patients should undergo CT scanning, resulting in a diagnostic cost reduction and reduced patient radiation exposure.

Superior Semicircular Canal Dehiscence by Superior Petrosal Sinus: Proposal for Classification.

This study aimed to present 3 different clinical stages in patients presenting with superior semicircular canal dehiscence (SSCD) by the superior petrosal sinus (SPS). A specific 3-class classification based on clinical, radiological, and audio-vestibular arguments is proposed. We retrospectively compared clinical and radiological findings in 3 patients with different degrees of audio-vestibular dysfunction in whom the imagery evocated the diagnosis of SSCD by SPS. Imaging sensitivity was improved by combining inner ear high-resolution computed tomography (HRCT) scan and magnetic resonance imaging in fusion, allowing us to compare and corroborate clinical and audio-vestibular findings in each case with the imagery. HRCT and 3T inner ear fusion imaging highlighted a direct contact and/or compression between SPS and the membranous superior semicircular canal (SSC). We propose a new classification of SSCD by SPS. Class "A" corresponds to an HRCT image with a "cookie bite" and thin bone still covering the SSC. Class "B" corresponds to a "cookie bite" image with confirmed contact between the SPS wall and the membranous SSC in MRI labyrinthine sequences. Class "C" type corresponds to a "cookie bite" image, contact, and obvious compression of the membranous SSC by SPS on MRI sequences. Anatomical systematization is needed for daily practice. This classification of SSCD by SPS would contribute to a better understanding of the wide variety and variability in the occurrence and onset of symptoms.

Superior semicircular canal dehiscence syndrome: Diagnostic criteria consensus document of the committee for the classification of vestibular disorders of the Bárány Society

This paper describes the diagnostic criteria for superior semicircular canal dehiscence syndrome (SCDS) as put forth by the classification committee of the Bárány Society. In addition to the presence of a dehiscence of the superior semicircular canal on high resolution imaging, patients diagnosed with SCDS must also have symptoms and physiological tests that are both consistent with the pathophysiology of a ‘third mobile window’ syndrome and not better accounted for by another vestibular disease or disorder. The diagnosis of SCDS therefore requires a combination of A) at least one symptom consistent with SCDS and attributable to ‘third mobile window’ pathophysiology including 1) hyperacusis to bone conducted sound, 2) sound-induced vertigo and/or oscillopsia time-locked to the stimulus, 3) pressure-induced vertigo and/or oscillopsia time-locked to the stimulus, or 4) pulsatile tinnitus; B) at least 1 physiologic test or sign indicating that a ‘third mobile window’ is transmitting pressure including 1) eye movements in the plane of the affected superior semicircular canal when sound or pressure is applied to the affected ear, 2) low-frequency negative bone conduction thresholds on pure tone audiometry, or 3) enhanced vestibular-evoked myogenic potential (VEMP) responses (low cervical VEMP thresholds or elevated ocular VEMP amplitudes); and C) high resolution computed tomography (CT) scan with multiplanar reconstruction in the plane of the superior semicircular canal consistent with a dehiscence. Thus, patients who meet at least one criterion in each of the three major diagnostic categories (symptoms, physiologic tests, and imaging) are considered to have SCDS.