Superior Canal Dehiscence Effect on Hearing Thresholds: Animal Model (original) (raw)
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Superior semicircular canal dehiscence mimicking otosclerotic hearing loss
Advances in oto-rhino-laryngology, 2007
A puzzling aspect of middle ear surgery is the presence of an air-bone gap in a small number of cases with no apparent cause. We believe that some of these cases are due to unrecognized superior semicircular canal dehiscence (SSCD). We have now gathered experience from 20 patients with SSCD presenting with apparent conductive hearing loss without vestibular symptoms. All affected ears had SSCD on high-resolution CT scan. The common findings in these patients were: (1) the air-bone gaps occurred in the lower frequencies below 2,000 Hz, and ranged from 10 to 60 dB; (2) bone conduction thresholds below 2,000 Hz were sometimes negative (-5 dB to -15 dB); (3) the acoustic (stapedial) reflex was present; (4) measurement of umbo velocity by laser Doppler vibrometry showed slight hypermobility of umbo motion; (5) the vestibular-evoked myogenic potential response was present, with thresholds that were abnormally low, and (6) the middle ear was normal at exploratory tympanotomy, including nor...
The Effect of Superior Semicircular Canal Dehiscence on Intracochlear Sound Pressures
Audiology and Neurotology, 2012
decreased by about 10 dB for a 0.5-mm dehiscence and by 20 dB for a 2-mm dehiscence, while ST decreased by about 8 dB for a 0.5-mm dehiscence and by 18 dB for a 2-mm dehiscence. Differential pressure decreased by about 10 dB for a 0.5-mm dehiscence and by about 20 dB for a 2-mm dehiscence at 100 Hz. In some ears, for frequencies above 1 kHz, the smallest pinpoint dehiscence had bigger effects on the differential pressure (10-dB decrease) than larger dehiscences (less than 10-dB decrease), suggesting larger hearing losses in this frequency range. These effects due to SCD were reversible by patching the dehiscence. We also showed that under certain circumstances such as SCD, stapes velocity is not related to how the ear can transduce sound across the cochlear partition because it is not directly related to the differential pressure, emphasizing that certain pathologies cannot be fully assessed by measurements such as stapes velocity.
Audiology & neuro-otology, 2015
Superior canal dehiscence (SCD) is a defect in the bony covering of the superior semicircular canal. Patients with SCD present with a wide range of symptoms, including hearing loss, yet it is unknown whether hearing is affected by parameters such as the location of the SCD. Our previous human cadaveric temporal bone study, utilizing intracochlear pressure measurements, generally showed that an increase in dehiscence size caused a low-frequency monotonic decrease in the cochlear drive across the partition, consistent with increased hearing loss. This previous study was limited to SCD sizes including and smaller than 2 mm long and 0.7 mm wide. However, the effects of larger SCDs (>2 mm long) were not studied, although larger SCDs are seen in many patients. Therefore, to answer the effect of parameters that have not been studied, this present study assessed the effect of SCD location and the effect of large-sized SCDs (>2 mm long) on intracochlear pressures. We used simultaneous ...
The relationship between the air-bone gap and the size of superior semicircular canal dehiscence
Otolaryngology - Head and Neck Surgery, 2009
To examine the relationship between the air-bone gap (ABG) and the size of the superior semicircular canal dehiscence (SSCD) as measured on a computed tomography (CT) scan. STUDY DESIGN: Case series with chart review. SETTING: Tertiary referral center. PATIENTS: Twenty-three patients (28 ears) diagnosed with SSCD. MAIN OUTCOME MEASURES: The size of the dehiscence on CT scans and the ABG on pure-tone audiometry were recorded. RESULTS: The size of the dehiscence ranged from 1.0 to 6.0 mm (mean, 3.5 Ϯ 1.6 mm). Six ears with a dehiscence measuring less than 3.0 mm did not have an ABG (0 dB). The remaining 18 ears showed an average ABG at 500, 1000, and 2000 Hz (AvABG 500-2000 ) ranging from 3.3 to 27.0 dB (mean, 11.6 Ϯ 5.7 dB). The analysis of the relationship between the dehiscence size and AvABG 500-2000 revealed a correlation of R 2 ϭ 0.828 (P Ͻ 0.001, quadratic fit) and R 2 ϭ 0.780 (P Ͻ 0.001, linear fit). Therefore, the larger the dehiscence, the larger the ABG at lower frequencies on pure-tone audiometry. CONCLUSIONS: In SSCD patients, an ABG is consistently shown at the low frequency when the dehiscence is larger than 3 mm. The size of the average ABG correlates with the size of the dehiscence. These findings highlight the effect of the dehiscence size on conductive hearing loss in SSCD and contribute to a better understanding of the symptomatology of patients with SSCD.
A superior semicircular canal dehiscence-induced air-bone gap in chinchilla
Hearing Research, 2010
An SCD is a pathologic hole (or dehiscence) in the bone separating the superior semicircular canal from the cranial cavity that has been associated with a conductive hearing loss in patients with SCD syndrome. The conductive loss is defined by an audiometrically determined air-bone gap that results from the combination of a decrease in sensitivity to air-conducted sound and an increase in sensitivity to bone-conducted sound. Our goal is to demonstrate, through physiological measurements in an animal model, that mechanically altering the superior semicircular canal (SC) by introducing a hole (dehiscence) is sufficient to cause such an air-bone gap. We surgically introduced holes into the SC of chinchilla ears and evaluated auditory sensitivity (cochlear potential) in response to both air-and bone-conducted stimuli. The introduction of the SC hole led to a low-frequency (< 2000 Hz) decrease in sensitivity to air-conducted stimuli and a low-frequency (< 1000 Hz) increase in sensitivity to bone-conducted stimuli resulting in an air-bone gap. This result was consistent and reversible. The air-bone gaps in the animal results are qualitatively consistent with findings in patients with SCD syndrome.
Superior semicircular canal dehiscence syndrome
Journal of Neurosurgery, 2004
Objective: The aim of this investigation was to determine if there is any association between the size of the canal dehiscences and the symptoms and signs of patients presenting with the superior semicircular canal dehiscence syndrome. Study Design: Prospective multicenter study. Setting: Tertiary referral center. Patients: Twenty-seven patients, 14 females and 13 males, aged 25 to 83 years, coming from Switzerland, France, Belgium, or Italy, with dehiscence of the superior semicircular canal diagnosed by high-resolution computed tomographic scans of the temporal bone. Interventions: Audiologic tests, a battery of vestibular tests (Tullio phenomenon, Hennebert sign, Valsalva maneuver), vestibular evoked myogenic potentials (VEMPs), and highresolution computed tomographic scans of the temporal bone. Main Outcome Measures: Association between the symptoms/ signs and the size of the superior canal dehiscence. Results: Clinically patients could be divided into three different groups: Superior canal dehiscences (Q2.5 mm) presented pre-dominantly with cochleovestibular symptoms and/or signs (sensitivity, 91.7%; specificity, 70%), whereas smaller one_s showed either cochlear or vestibular dysfunction. Patients with larger dehiscences were significantly more associated with vestibulocochlear symptoms/signs, lower VEMP thresholds, and objective vestibular findings (e.g., Tullio phenomenon) than subjects with smaller bony defects. No significant association between the size of the dehiscence and the audiogram pattern or individual findings could be found. The location of the dehiscence seemed to have no influence on the clinical manifestation and findings. Conclusion: Patients with larger superior canal dehiscences show significantly more vestibulocochlear symptoms/signs, lower VEMP thresholds, and objective vestibular findings compared with smaller ones. Smaller dehiscences mainly present with either cochlear or vestibular dysfunction. Key Words: Conductive hearing lossVDizzinessVInner earVSuperior semicircular canal dehiscenceVVertigo.
Annals of the Academy of Medicine, Singapore, 2011
This study aimed to examine the relationship between the air-bone gap (ABG) and the size of the superior semicircular canal dehiscence (SSCD) as measured on a computed tomography (CT) scan. The study design was a case series with chart review. Twenty-three patients (28 ears) from a tertiary referral centre were diagnosed with SSCD. The size of the dehiscence on CT scans and the ABG on pure-tone audiometry were recorded. The size of the dehiscence ranged from 1.0 to 6.0 mm (mean, 3.5 ± 1.6 mm). Six ears with a dehiscence measuring less than 3.0 mm did not have an ABG (0 dB). The remaining 18 ears showed an average ABG at 500, 1000, and 2000 Hz (AvABG(500-2000)) ranging from 3.3 to 27.0 dB (mean, 11.6 ± 5.7 dB). The analysis of the relationship between the dehiscence size and AvABG(500-2000) revealed a correlation of R(2) = 0.828 (P <0.001, quadratic fit) and R(2) = 0.780 (P <0.001, linear fi t). Therefore, the larger the dehiscence, the larger the ABG at lower frequencies on pu...
Characterization of Bilateral Superior Canal Dehiscence
Acta Otorrinolaringologica (English Edition), 2007
In the superior semicircular canal (SSC) dehiscence syndrome, patients can have sound-or pressure-induced vertigo and oscillopsia. They may also present conductive hearing loss or higher than normal bone conduction thresholds. Clinical manifestations are due to the effect of a third mobile window in the inner ear created by the dehiscence. Diagnosis is based on clinical manifestations, vertical and rotatory nystagmus induced by sound and pressure reflecting SSC stimulation, reduced threshold and increased amplitude of vestibular evoked myogenic potentials (VEMP) and temporal bone CT scan images showing the SSC dehiscence. Characteristic eye movements can be recorded with the scleral search coil technique.