Three-dimensional computed tomography of superior canal dehiscence syndrome
ABSTRACT To compare 3-dimensional (3-D) surface reconstructions of the temporal bone with presently used multiplanar reconstructions (MPRs) from high-resolution computed tomographic (HRCT) data sets in patients with superior canal dehisence syndrome (SCDS). Results of audiometry, vestibular evoked myopotentials (VEMPs), and clinical testing are also considered.
: Twenty-one adults with unilateral or bilateral SCD.
High-resolution computed tomographic scans, audiograms, VEMP testing.
Comparison of findings on 3-D surface reconstructions with MPRs; predictive values of different tests.
High-resolution computed tomographic scans were performed on 6 subjects with bilateral SCD and 15 with unilateral SCD. High-resolution computed tomographic scans were examined as MPRs in the plane of the SC and in perpendicular radial cuts through the SC. High-resolution computed tomographic scans were also analyzed as 3-D surface reconstructions. Compared with the MPRs, 3-D surface reconstructions for patients who had at least 1 objective finding suggestive of SCDS had a 68% positive predictive value, 91% sensitivity, and 47% specificity. None of those temporal bones that had intact SCs on MPRs had other objective findings suggestive of SCDS. Three-dimensional surface reconstructions often made SCs covered with thin bone seem dehiscent, exposed air cells can be mistaken for SCDS, and a large dehiscence can sometimes be missed. Nystagmus evoked by 110-dB relative-to-normal-hearing-level tones was 100% specific for SCDS when present but only 67% sensitive. Decreased click evoked VEMP threshold was 80% sensitive and 80% specific for SCDS. Conductive hearing loss of 10 dB or greater had an 83% sensitivity and 95% specificity.
Multiplanar reconstructions of HRCT data are the most sensitive test for diagnosis of SCD. False SCD and missed SCD can occur with 3-D surface reconstructions of the temporal bone. Determination of SCD should be based on MPRs of an HRCT data instead of 3-D surface reconstructions, but the latter remain valuable for surgical planning. The decision for surgery in SCDS should not be based on imaging results alone but also on the physiologic findings and the frequency and severity of symptoms.
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ABSTRACT: KP-1699-A-Klamath Project. Seepage Investigation. Seepage on Type "D" Construction; June 21, 1948; Photo by Jack Jorgensen
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ABSTRACT: Superior semicircular canal syndrome (SSCS) includes vestibular and audiological symptoms which result from the introduction of a third mobile window into the osseous cochlea. Surgical repair is considered in cases of incapacitating symptoms. The present paper aims at comparing the different surgical approaches and modes of dehiscence repair, regarding their respective efficacy and potential pitfalls. A systematic literature review and meta-analysis of pooled data were performed. Study selection included prospective- and retrospective-controlled studies, prospective- and retrospective-cohort studies, ex vivo studies, animal models, case-reports, systematic reviews and clinical guidelines. A total of 64 primary operations for SSC repair were identified; 56 ears were operated for vestibular and 7 for auditory complaints. A total of 33 ears underwent canal plugging, 16 resurfacing, and 15 capping. Success rates were 32/33, 8/16, and 14/15, respectively. The observed differences were statistically significant (P=0.001). Resurfacing proved less effective than both plugging (P=0.002), and capping (P=0.01) techniques. Temporalis fascia was commonly used as sealing material and was combined with bone-pâté/bone-wax (plugging), bone-graft (resurfacing), or hydroxyapatite-cement (capping). Most operations were performed via middle-fossa approach; higher success rates were associated with plugging and capping techniques. SNHL and disequilibrium were the most frequent complications encountered. Most cases were followed for 3-6 months. Precise criteria regarding follow-up duration and objective success measures are not determined. Surgical repair of SSCS is considered as a valid therapeutic option for patients with debilitating symptoms. Consensus regarding strict follow-up criteria and objective assessment of success is necessary before larger scale operations can be implemented in clinical practice.Archives of Oto-Rhino-Laryngology 11/2008; 266(2):177-86. DOI:10.1007/s00405-008-0840-4 · 1.61 Impact Factor
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ABSTRACT: 1) Determine the prevalence of vestibular hypofunction in the immediate postoperative period after surgical treatment of superior semicircular canal dehiscence syndrome. 2) Evaluate whether dehiscence length is associated with risk of postoperative vestibular hypofunction. 3) Compare the prevalences of immediate and late postoperative vestibular hypofunction. Clinical review. Tertiary referral center. Subjects with superior canal dehiscence syndrome (n = 42) based on history, physiologic testing, and computed tomography findings, who underwent middle fossa craniotomy and superior canal dehiscence plugging. Dehiscence length was measured intraoperatively. Bedside horizontal head thrust testing (hHTT) was administered between postoperative days 1 to 7 to diagnose immediate postoperative vestibular hypofunction. Both hHTT and quantitative vestibulo-ocular reflex testing were administered 6 to 29 weeks postoperatively to detect late vestibular hypofunction. Dehiscence length and hypofunction in response to hHTT. Thirty-eight percent of the subjects (95% confidence interval, 25-54) had hypofunction in response to hHTT within 1 week after surgery. Mean dehiscence lengths were 4.9 (range, 2.0-10.5 mm) and 3.4 mm (range, 1.0-5.5 mm) in subjects with and without postoperative hypofunction, respectively (p = 0.0018). Each 1-mm increase in dehiscence length increased the odds of immediate postoperative hypofunction 2.6-fold (95% confidence interval, 1.3-5.1). The prevalence of vestibular hypofunction was significantly higher in the early compared with the late postoperative period. Immediate postoperative vestibular hypofunction is common, particularly with larger dehiscences. This hypofunction may typically resolve, given that the prevalence of vestibular hypofunction 6 weeks postoperatively is low. Possible mechanisms include intraoperative loss of perilymph, which may be more likely with larger dehiscences.Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology 04/2009; 30(4):502-6. DOI:10.1097/MAO.0b013e3181a32d69 · 1.60 Impact Factor