Superior Semicircular Canal Dehiscence Patients 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.

Investigation of serum calcium and vitamin D levels in superior semicircular canal dehiscence syndrome: A case control study

ObjectiveIt remains unknown whether calcium metabolism has any effect on the clinical presentation of superior semicircular canal dehiscence (SSCD). Our aim was to analyse the adjusted calcium and vitamin D levels in SSCD patients compared to a control group. MethodsThis was a prospective case-control study performed in a tertiary referral center, university teaching hospital in the UK. It included all new patients with SSCD seen in a dedicated skull base clinic over a 5-year period (2015–2019) compared to a gender and age matched control group. The main outcome of the study was adjusted calcium and Vitamin D levels between the two groups. ResultsA total of 31 SSCD patients were recruited with a matched number of control patients. The mean Vitamin D level on the SSCD group was 44.8 nmoL/l (SD: 20.8) compared to 47.5 nmoL/l (SD: 27.4) on the control group (p = 0.702). Mean Adjusted calcium level was 2.34 mmoL/l (SD: 0.7) for SSCD compared to 2.41 mmoL/l (SD: 0.11) for controls (p = 0.01), being within normal limits for both the SSCD and the control group. ConclusionOur study did not identify a link between Vitamin D levels and presence of SSCD. Normal adjusted calcium values were found in both groups. Despite that a statistically significant lower calcium level was found in the SSCD group which could indicate that suboptimal levels of calcium may affect the micro-environment of the otic capsule at the SSC region.

Evaluation of Superior Semicircular Canal Dehiscence Anatomical Location and Clinical Outcomes: A Single Institution's Experience

Superior semicircular canal dehiscence (SSCD) is becoming increasingly recognized as a pathology underlying various auditory and vestibular complaints. To date, our understanding of the pathology has yet to attribute specific symptoms to the anatomic location of dehiscence in patients with SSCD. This study aims to address this issue by evaluating the relationship between symptomatology and anatomic location of dehiscence. A single-institution retrospective review of SSCD patients was performed. Information was collected on patient demographics, symptomatology, and anatomic location of dehiscence. High-resolution computed tomography scans of the temporal bones were used to categorize the anatomic SSCD location into 1 of 3 groups: anterior limb, apex, and posterior limb. Lastly, we performed statistical analysis to determine the degree of association between each of the various perioperative factors and anatomic SSCD location. We studied 54 patients in total (32 women, 22 men). Mean age at diagnosis was 53 years (range: 20-82 years) and mean follow-up length was 5.5 months (range: 0.03-27.0 months). The most common anatomical location of superior semicircular canal dehiscence was the apex, which was seen in 68.5% of cases. While preoperative symptomatology was similar among the 3 cohorts, those with apical dehiscences had a significantly higher rate of postoperative improvement of autophony (P= 0.03), aural fullness (P= 0.03), and tinnitus (P= 0.05) as compared to their counterparts. Although our results do not support an association between preoperative characteristics-including symptomatology-and anatomic SSCD location, our findings do suggest that apical dehiscences are associated with greater postoperative symptomatic resolution.

Postoperative Outcomes of Patients with Thin Bone Overlying the Superior Semicircular Canal: A Single Institution's Experience

Superior semicircular canal dehiscence (SSCD) is defined by a bony defect overlying the superior semicircular canal (SSC) in the middle cranial fossa floor, causing a myriad of vestibular and auditory symptoms. Patients with thin bone without full dehiscence overlying the SSC also present with similar symptoms. There are currently no guidelines for surgical management of patients with thin bone. The authors offer their experience with thin bone patients to characterize their symptomatology and explore whether these patients benefit from surgical intervention typically offered to SSCD patients. Two hundred fifty-six patients evaluated for SSCD from 2011 to 2019 were reviewed. High-resolution coronal computed tomography scans with 0.6-mm slice thickness of the temporal bones were assessed to determine whether the patient had a true dehiscence or a thin bone covering overlying the SSC. Bone that was ≤0.5mm was considered to be "thin bone." Parameters of interest included patient demographics as well as preoperative and postoperative symptomatology. A P value < 0.05 was considered statistically significant. Forty-eight patients met inclusion criteria of having "thin bone." The mean age was 48.13±12.03years, and 65.5% of patients were female. Of the preoperative symptoms evaluated, the greatest postoperative symptomatic resolution was noted in hearing loss (92.3%), vertigo (94.4%), and oscillopsia (100%). Dizziness (56.5%) had the lowest symptomatic resolution rate. Surgical management of thin bone patients via middle fossa craniotomy, a similar technique to SSCD repair, provides significant symptomatic resolution. Therefore, surgery should be considered in thin bone patients with debilitating symptoms, albeit not having a true dehiscence.

Superior Semicircular Canal Dehiscence Revision Surgery Outcomes: A Single Institution's Experience

Superior semicircular canal dehiscence (SSCD) is an abnormality of the otic capsule, which normally overlies the superior semicircular canal. Surgical management is indicated in patients with persistent and debilitating symptoms. Given the complexity of the disease, there are patients who experience less favorable surgical outcomes and require revision surgery. The purpose of this study was to report to the rate of postoperative symptomatic improvement in patients who required revision surgery. A retrospective analysis of patients undergoing SSCD surgical repair at a single institution was performed. Information on patient demographics, primary and secondary surgical approaches, surgical outcomes, and follow-up length was collected. Seventeen patients underwent 20 revision surgeries. There were eleven (65%) females and six (35%) males. Mean age of the cohorts was 50 years (range 30-68 years), and mean follow-up length was 6.8 months (range 0.1-31.1 months). Cerebrospinal fluid leak was noted in 67% of cases. The greatest postoperative symptomatic resolution was reported in oscillopsia (100%), headache (100%), and internal sound amplification (71%), while the least postoperative symptomatic resolution was reported in tinnitus (42%), aural fullness (40%), and dizziness (29%). Revision surgery can provide symptomatic improvement in select SSCD patients; however, patients should be cautioned about the possibility of less favorable outcomes than in index surgery. Revision surgeries are associated with a considerably higher rate of perioperative cerebrospinal fluid leak.

Vestibular Evoked Myogenic Potential (VEMP) Testing for Diagnosis of Superior Semicircular Canal Dehiscence.

Superior semicircular canal dehiscence is a bony defect of the superior semicircular canal, which can lead to a variety of auditory and vestibular symptoms. The diagnosis of superior semicircular canal dehiscence (SCD) can be challenging, time consuming, and costly. The clinical presentation of SCD patients resembles that of other otologic disease, necessitating objective diagnostics. Although temporal bone CT imaging provides excellent sensitivity for SCD detection, it lacks specificity. Because the treatment of SCD is surgical, it is crucial to use a highly specific test to confirm the diagnosis and avoid false positives and subsequent unnecessary surgery. This review provides an update on recent improvements in vestibular evoked myogenic potential (VEMP) testing for SCD diagnosis. Combining audiometric and conventional cervical VEMP results improves SCD diagnostic accuracy. High frequency VEMP testing is superior to all other methods described to date. It is highly specific for the detection of SCD and may be used to guide decision-making regarding the need for subsequent CT imaging. This algorithmic sequential use of testing can substantially reduce radiation exposure as well as cost associated with SCD diagnosis.

Temporal Bone Anatomy in Superior Semicircular Canal Dehiscence: A Case Control Study on Bone Pneumatization and the Level of Middle Cranial Fossa.

To assess for any association between the presence of superior semicircular canal dehiscence (SSCD) and temporal bone pneumatization and the height of middle fossa in symptomatic patients. Retrospective case-control study. Tertiary, university referral center. Symptomatic patients with SSCD and a matched group of non-SSCD patients. High-resolution computed tomography of the temporal bones. We graded the temporal bone pneumatization using the Virapongse classification and measured the distance between the middle fossa and the lateral semicircular canal on coronal plane at the most anterior aspect of the lateral and superior semicircular canals. We statistically compared all parameters (level of significance 0.05). We enrolled 30 patients with SSCD, (males = 13, females = 17) with mean age of 47 years (SD: 26). The matched control group had similar baseline characteristics (p > 0.05). Grade 4 pneumatization was noted in 83.3% (n = 25) of SSCD patients with the remainder having grade 3. In the control group, 46.6% (n = 14) had a grade 4 pneumatization, 36.6% (n = 11) grade 3 and 16.6 5 (n = 5) grade 2. This difference was statistically significant (p = 0.003). The difference in the height of the middle cranial fossa between the two groups was also statistically significant (mean 3.80 [SD: 0.84] in SSCD group and 4.68 mm [SD: 0.85] in the control group; p < 0.0001). We found better-pneumatized mastoids in patients with SSCD, indicative of a direct association between temporal bone pneumatization and SSCD. Additionally, the middle fossa dura is lying significantly lower in patients with SSCD, factor of surgical importance.

Sealing of superior semicircular canal dehiscence is associated with improved balance outcomes postoperatively versus plugging of the canal in middle fossa craniotomy repairs: a case series.

The authors compared postoperative symptoms between patients with sealed and those with plugged semicircular canal dehiscence repairs. In total, 136 ears from 118 patients who underwent surgical repair for semicircular canal dehiscence were identified via chart review. Data from postoperative MRI scans showing preservation or loss of semicircular canal fluid signal and postoperative reports of autophony, amplification, aural fullness, tinnitus, hyperacusis, hearing loss, vertigo, dizziness, disequilibrium, oscillopsia, and headache were amalgamated and analyzed. Patients with preservation of fluid signal were far less likely to have dizziness postoperatively (p = 0.007, OR 0.158, 95% CI 0.041-0.611). In addition, these patients were more likely to have tinnitus postoperatively (p = 0.028, OR 3.515, 95% CI 1.145-10.787). The authors found that superior semicircular canal dehiscence patients who undergo sealing without plugging have improved balance outcomes but show more tinnitus postoperatively than patients who undergo plugging.

Age and gender considerations on the symptomology in patients with superior semicircular canal dehiscence: A systematic review and case illustration

Superior semicircular canal dehiscence (SSCD) is caused by a fistula in the arcuate eminence, creating vestibular and auditory disturbances. We aim to determine the effects of gender and age on symptom prevalence and resolution in patients with SSCD. A Boolean search was conducted through four separate scientific databases. Full-text English articles for SSCD patients, who underwent surgery were included. Demographics and outcomes were extracted. A total of 198 patients were identified, and available for quantitative analysis. Between genders, there were no differences in the prevalence of pre- or post-operative symptomology. Both genders had statistically significant improvement in symptomatology with females experiencing significantly high rates of hearing loss improvement compared to male patients. Compared to their younger cohort, patients over 65 had similar symptom frequencies before and after surgery with similar rates of symptom resolution. SSCD repair is safe and effective for resolving auditory and vestibular symptoms. Gender and age may not be strong predictors of patient presentation or symptom resolution. Gender and age-associated factors may not influence patient outcomes.

Toward Optimizing cVEMP: 2,000-Hz Tone Bursts Improve the Detection of Superior Canal Dehiscence

Background: The cervical vestibular evoked myogenic potential (cVEMP) test measures saccular and inferior vestibular nerve function. The cVEMP can be elicited with different frequency stimuli and interpreted using a variety of metrics. Patients with superior semicircular canal dehiscence (SCD) syndrome generally have lower cVEMP thresholds and larger amplitudes, although there is overlap with healthy subjects. The aim of this study was to evaluate which metric and frequency best differentiate healthy ears from SCD ears using cVEMP. Methods: Twenty-one patients with SCD and 23 age-matched controls were prospectively included and underwent cVEMP testing at 500, 750, 1,000 and 2,000 Hz. Sound level functions were obtained at all frequencies to acquire threshold and to calculate normalized peak-to-peak amplitude (VEMPn) and VEMP inhibition depth (VEMPid). Third window indicator (TWI) metrics were calculated by subtracting the 250-Hz air-bone gap from the ipsilateral cVEMP threshold at each frequency. Ears of SCD patients were divided into three groups based on CT imaging: dehiscent, thin or unaffected. The ears of healthy age-matched control subjects constituted a fourth group. Results: Comparing metrics at all frequencies revealed that 2,000-Hz stimuli were most effective in differentiating SCD from normal ears. ROC analysis indicated that for both 2,000-Hz cVEMP threshold and for 2,000-Hz TWI, 100% specificity could be achieved with a sensitivity of 92.0%. With 2,000-Hz VEMPn and VEMPid at the highest sound level, 100% specificity could be achieved with a sensitivity of 96.0%. Conclusion: The best diagnostic accuracy of cVEMP in SCD patients can be achieved with 2,000-Hz tone burst stimuli, regardless of which metric is used.

Can Wideband Tympanometry Be Used as a Screening Test for Superior Semicircular Canal Dehiscence?

Objectives We explored whether wideband tympanometry (WBT) could be used as a screening test for superior semicircular canal dehiscence (SSCD), and obtained new WBT data (given that the test is not yet in common clinical use) on patients with SSCD.Methods We compared the WBT data of patients clinically and radiologically diagnosed with SSCD in our hospital between 2013 and 2018 to those of healthy volunteers. We compared the resonance frequency (RF), maximum absorbance frequency (MAF), and maximum absorbance ratio (MAR). The t-test was used for statistical analysis with the significance level set to P<0.05. In addition, we used receiver operating characteristic analysis to derive cutoff values for SSCD diagnosis in terms of sensitivity and specificity.Results Seventeen patients (four with bilateral and 13 with unilateral disease; 17 ears) diagnosed with SSCD and 27 healthy volunteers (47 ears) were included. The mean RFs of the SSCD patients and healthy subjects were 548.7 Hz (range, 243 to 853 Hz) and 935.1 Hz (range, 239 to 1,875 Hz), respectively (P<0.001). The mean MARs of the SSCD patients and healthy subjects were 89.4% (range, 62% to 100%) and 82.4% (range, 63% to 99%), respectively (P=0.005). The mean MAFs of the SSCD patients and healthy subjects were 1,706.3 Hz (range, 613 to 3,816 Hz) and 2,668 Hz (range, 876 to 4,387 Hz), respectively (P<0.001). In terms of SSCD diagnosis, a MAR above 86% afforded 81% sensitivity and 77% specificity; an RF below 728 Hz, 86% sensitivity and 81% specificity; and an MAF below 1,835 Hz, 79% sensitivity and 67% specificity.Conclusion WBT may be a useful clinical screening test for SSCD. The RF and MAF were lower, and the MAR higher, in SSCD patients than in normal controls.

Bone Metabolic Markers in the Clinical Assessment of Patients with Superior Semicircular Canal Dehiscence

Superior semicircular canal dehiscence (SSCD) is a bony defect in the osseous shell of the petrous temporal bone. The pathophysiological association between osteoporosis and SSCD remains poorly understood. We investigated the relationship between bone metabolic markers and symptoms in patients with SSCD. We collected patient demographics and clinical parameters for adult patients diagnosed with SSCD on high-resolution computed tomography scans. We used point-biserial correlation analysis to investigate the relationship between bone metabolic markers and symptoms in patients with SSCD. We compared clinical symptoms before and after surgical repair of SSCD through a middle fossa craniotomy using McNemar's test for paired comparisons of binary measures. We included a total of 99 patients (64 females and 35 males; average age 52 years; 118 surgeries). The level of serum calcium correlated with the need for a second surgery (rpb=-0.35, P= 0.001). Postoperative calcium supplementation negatively correlated with improvement in dizziness (rpb=-0.36, P= 0.01). The level of 25-hydroxyvitamin D correlated with preoperative hyperacusis (rpb=-0.98, P= 0.02) and postoperative autophony (rpb= 0.96, P= 0.04). Postoperative vitamin D supplementation positively correlated with hearing decline (rpb= 0.04, P= 0.04) The level of thyroid stimulating hormone correlated withpreoperative autophony, amplification, and tinnitus (rpb=-0.71, rpb=-0.75, rpb=-0.70, all P < 0.001). Bone metabolic markers could be important in the clinical assessment of SSCD patients and could be potential targets for symptom management.

Outcomes of middle fossa craniotomy for the repair of superior semicircular canal dehiscence

Superior semicircular canal dehiscence (SSCD) is a rare defect of the arcuate eminence that causes an abnormal connection between the superior semicircular canal and middle cranial fossa. Patients often present with a variety of auditory and vestibular symptoms. Trigger avoidance is the initial strategy, but surgery may be necessary in debilitating cases. We retrospectively reviewed SSCD patients undergoing repair via a middle fossa craniotomy between March 2011 and September 2015. Forty-nine patients undergoing 58 surgeries were identified. Autophony was the most common symptom at presentation (n=44; 90%). Mean follow-up was 10.9months, with 100% of patients reporting resolution of at least one symptom. Aural fullness was the most commonly resolved symptom following surgical repair (n=19/22; 86%). Hearing loss (n=11/25; 44%) and tinnitus (n=11/38; 29%) were the most common symptoms to persist following surgery. The most common symptom to develop after surgery was disequilibrium (n=4/18; 22%). Upon comparing the overall pre-operative and post-operative groups, the number of patients with autophony (p<0.0001), aural fullness (p=0.0006), hearing loss (p=0.0119), disequilibrium (p=0.0002), sound- and pressure-induced vertigo (p<0.0001), and tinnitus (p<0.0001) were significantly different. Improved clinical outcomes were demonstrated in patients undergoing SSCD repair through a middle cranial fossa approach. The most common presenting symptom (autophony) was also most likely to resolve after surgery. Hearing loss is less amenable to surgical correction. Disequilibrium developed in a small number of patients after repair.

Skull vibration induced nystagmus frequency and location optimization in severe unilateral lesion patients and in anterior canal dehiscences

Background Bone conducted vibrations (BCV) applied on mastoid elicit in common unilateral vestibular lesion (UVL) patients usually a skull vibration induced nystagmus (SVIN) beating toward the intact side and conversely in unilateral superior semicircular canal dehiscence (SCD) a SVIN beating toward the lesion side. Our purpose was to establish optimal topographic and frequency stimulations in severe UVL (SUVL) and SCD patients. The second aim was to compare VIN at 100 Hz in unilateral SCD (uSCD) and bilateral (bSCD) patients. Participants and methods The first experiment included 11 SUVL and 10 unilateral SCD (uSCD). The SVIN, optimal frequency was studied with a MiniShaker BK the VIN slow phase velocity (SPV) was recorded with Videonystagmography. Optimal topographic stimulation study analyzed vertex and mastoids responses SPV at 100 Hz. Second experiment included 27 uSCD and 13 bSCD and analyzed SVIN SPV at 100 Hz. Results In SUVL, the optimal stimulus frequency was 100 Hz for the horizontal component VIN SPV ( P P = 0.02) and at 600 Hz ( P = 0.01); conversely VIN SPV at 100 Hz was higher in SUVL than uSCD ( P = 0.008). In SUVL, mastoid stimulation was significantly more efficient than vertex stimulation (ANOVA P = 0.01). Conversely, in uSCD SVIN SPV was significantly higher after vertex stimulation ( P = 0.04). A VIN was significantly more often observed in uSCD than bSCD ( P = 0.009) and VIN SPV was higher in uSCD than bSCD ( P = 0.008). Conclusion In SUVL, the optimal frequency stimulation is 100 Hz with no responses over 500 Hz. In SCD, patients responses are observed up to 700 Hz without significant optimal frequency suggesting that the BC facilitation related to the existence of a third window enables a greater sensitivity to higher range of frequencies. Vertex stimulations are more efficient in SCD patients and higher responses are observed in uSCD than bSCD. SVIN acts as a vestibular Weber test.

Round window reinforcement for superior semicircular canal dehiscence: A retrospective multi-center case series

PurposeTo evaluate the outcome of round window (RW) tissue reinforcement in the management of superior semicircular canal dehiscence (SSCD). Materials and methodsTwenty-two patients with confirmed diagnosis of SSCD by clinical presentation, imaging, and/or testing were included in the study. Six surgeons at four institutions conducted a multicenter chart review of patients treated for symptomatic superior canal dehiscence using RW tissue reinforcement or complete RW occlusion. A transcanal approach was used to reinforce the RW with various types of tissue. Patients completed a novel postoperative survey, grading preoperative and postoperative symptom severity. ResultsAnalysis revealed statistically significant improvement in all symptoms with the exception of hearing loss in 19 patients who underwent RW reinforcement. In contrast, 2 of 3 participants who underwent the alternate treatment of RW niche occlusion experienced worsened symptoms requiring revision surgery. ConclusionRW tissue reinforcement may reduce the symptoms associated with SSCD. The reinforcement technique may benefit SSCD patients by reducing the “third window” effect created by a dehiscent semicircular canal. Given its low risks compared to middle cranial fossa or transmastoid canal occlusion, RW reinforcement may prove to be a suitable initial procedure for intractable SSCD. In contrast, complete RW occlusion is not advised.

Posterior Semicircular Canal Dehiscence

To estimate the prevalence of and symptoms associated with posterior semicircular canal dehiscence (PSCD) compared to superior semicircular canal dehiscence (SSCD) and nondehiscent semicircular canals (NDSC). Retrospective review. Academic tertiary referral center. Review of 412 temporal bone CT scans and associated patient records, excluding patients with prior mastoid or skull base surgery. CT images (0.625 mm thick) were reviewed in the planes of the semicircular canals. Patient demographics and symptoms were tabulated and analyzed. Prevalence of PSCD and SSCD; degree of hearing loss; presence or absence of aural fullness, autophony, tinnitus, pulsatile tinnitus, disequilibrium, vertigo, and Tullio phenomenon. Review of the 412 CT scans revealed 5 cases of PSCD (1.2%) and 20 cases of SSCD (4.9%). All patients with PSCD were male, aged 16 to 73 years. One patient with PSCD reported tinnitus, autophony, disequilibrium, vertigo, and Tullio phenomenon; 2 patients reported only tinnitus and aural fullness, and 1 patient had no symptoms. PSCD was commonly associated with SSCD. There were no significant differences in symptoms between PSCD patients and the other groups. There were, however, statistically significant differences between SSCD patients and NDSC patients in the rates of autophony, tinnitus, and disequilibrium. The prevalence of PSCD in patients undergoing temporal bone CT scans is considerably less than SSCD (1.2% versus 4.9%), and the 2 conditions commonly coexist. Given the small numbers in our study, we were not able to demonstrate any distinguishable clinical features for the PSCD patients.

Cochlear implant outcomes in patients with superior canal dehiscence

ObjectiveTo determine whether adult cochlear implant (CI) users with superior canal dehiscence syndrome (SCDS) or asymptomatic superior semicircular canal dehiscence (SCD) have different surgical, vestibular, and audiologic outcomes when compared to CI users with normal temporal bone anatomy.MethodsA retrospective single institution review of CI users with either superior semicircular canal dehiscence syndrome or asymptomatic superior semicircular canal dehiscence identified eight post-lingually deafened adults with unilateral or bilateral cochlear implantation between 2006 and 2010. Preoperative and postoperative speech perception scores as well as medical and epidemiological data were recorded and analyzed.ResultsOne patient with superior canal dehiscence syndrome and seven patients with asymptomatic superior semicircular canal dehiscence were identified, representing 7% or 8/113 of CI patients that fulfilled selection criteria. Average dehiscence length was 3.3 mm ± 0.79 SEM. Three patients received bilateral implants and five patients received a unilateral implant. Among asymptomatic superior semicircular canal dehiscence patients, subjective rates of post-operative dizziness were similar to those seen in patients with normal temporal bone anatomy (12.5 % vs. 15.9%, respectively). Speech perception abilities after surgery were poorer in SCD patients compared to the non-SCD cohort (Consonant Nucleus Consonant 33.7 ± 7.78 SEM vs. 56.7 ± 2.15 SEM P = 0.011), although both groups improved substantially relative to pre-operative performance. We also completed detailed analyses of auditory and vestibular outcomes in one patient with SCDS who underwent CI surgery in the symptomatic ear, which demonstrated preservation of vestibular function post-operatively, improved quality-of-life measures, and reduced dizziness symptomatology.ConclusionsOur data suggest that patients with asymptomatic superior canal dehiscence at the time of CI surgery have similar albeit decreased speech perception scores compared to non-SCD adult CI users. Subjective rate of dizziness or vertigo following CI surgery was similar in both asymptomatic SCD and non-SCD cohorts, with detailed analyses of a single symptomatic SCD patient revealing improved vestibular function and reduced SCD symptoms following CI.

An Indicator of Probable Semicircular Canal Dehiscence: Ocular Vestibular Evoked Myogenic Potentials to High Frequencies

The n10 component of the ocular vestibular evoked myogenic potential (oVEMP) to sound and vibration stimuli is a crossed response that has enhanced amplitude and decreased threshold in patients with CT-verified superior semicircular canal dehiscence (SSCD). However, demonstrating enhanced VEMP amplitude and reduced VEMP thresholds requires multiple trials and can be very time consuming and tiring for patients, so a specific indicator of probable SCD that is fast and not tiring would be preferred. Here we report a 1-trial indicator: that the oVEMP n10 in response to a very high frequency stimulus (4000 Hz), either air-conducted sound (ACS) or bone conducted vibration (BCV), is such a fast indicator of probable SCD. In 22 healthy subjects, oVEMP n10 at 4000 Hz was not detectable; however, in all 22 CT-verified SSCD patients tested, oVEMP n10 responses were clearly present to 4000 Hz to either ACS or BCV stimuli.

Transmastoid semicircular canal occlusion: A safe and highly effective treatment for benign paroxysmal positional vertigo and superior canal dehiscence

Transmastoid occlusion of the superior semicircular canal in superior semicircular canal dehiscence (SSCD) syndrome and the posterior semicircular canal in intractable benign paroxysmal positional vertigo (BPPV) will produce resolution of preoperative symptoms. Retrospective review, quality assurance. Sixteen patients with SSCD and 61 patients (65 ears) with intractable BPPV who underwent canal occlusion were reviewed. All patients underwent occlusion of the affected semicircular canal through a transmastoid approach. Preoperative symptoms (vestibular, 13 patients; pulsatile tinnitus, 2 patients; or hyperacusis, 1 patient) were greatly improved or completely resolved in 15 of the 16 SSCD patients who underwent transmastoid occlusion of the superior canal. Hearing was preserved in 14 patients and improved in two patients. Vestibular symptoms were resolved in all intractable BPPV patients who underwent transmastoid occlusion of the posterior canal. One patient had a late recurrence of atypical BPPV. Almost all BPPV patients with normal preoperative hearing have an initial transient postoperative hearing loss, which when tested for is usually a mild to moderate mixed loss. Delayed sensorineural hearing loss was noted in three patients; one loss was profound whereas two were mild. The transmastoid approach to canal plugging is successful in the treatment of symptoms in both SSCD and intractable BPPV, and is a familiar approach for the otologist. This is a viable alternative to the middle fossa approach for SSCD, thereby avoiding a craniotomy. Transmastoid is the definitive approach for posterior canal occlusion.

Ocular and Cervical Vestibular Evoked Myogenic Potentials to 500 Hz Fz Bone-Conducted Vibration in Superior Semicircular Canal Dehiscence

The aim of this study was to investigate the effect of superior semicircular canal dehiscence (SSCD) on the n10 component of the ocular vestibular evoked myogenic potential (oVEMP n10) and the p13-n23 component of the cervical vestibular evoked myogenic potential (cVEMP p13-n23) evoked by 500 Hz bone-conducted vibration (BCV) at the midline forehead at the hairline (Fz) in 26 patients with computed tomography-verified SSCD. Previous evidence has led to the proposal that the oVEMP n10 is of utricular origin whereas the cVEMP p13-n23 is of saccular origin. The question is can the oVEMP n10 to 500 Hz BCV indicate SSCD? A hand-held Bruel & Kjaer 4810 Minishaker was used to provide BCV stimulation using surface electromyography electrodes to record oVEMP n10 and cVEMP p13-n23. The stimulus was 7 msec bursts of 500 Hz BCV at either Fz or at the vertex of the skull (Cz). Twenty-seven healthy subjects were tested in the same paradigm. In response to 500 Hz Fz BCV in SSCD patients the oVEMP n10 amplitude beneath the contraSSCD eye was substantially and significantly larger than the oVEMP n10 beneath the ipsiSSCD eye, whereas in these same patients the cVEMP p13-n23 amplitude over the ipsiSSCD sternocleidomastoid muscle to Fz BCV was slightly but significantly larger than the cVEMP p13-n23 amplitude over the contraSSCD sternocleidomastoid muscle. In SSCD patients there was a significant relationship between the size of the dehiscence and the amplitude of the contralateral oVEMP n10 potential. The oVEMP n10 to Cz stimulation was still present in SSCD patients, but small or absent in healthy subjects. In response to 500 Hz Fz BCV an asymmetrical oVEMP n10 with a significantly increased amplitude of contralesional oVEMP n10 (compared with population values of healthy subjects) is a simple useful indicator of SSCD, confirmed by the Cz response. oVEMP testing with 500 Hz Fz BCV allows very simple, very fast identification of a probable unilateral SSCD.