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: We investigated if current-generation computed tomographic (CT) scanners have the resolution required to objectively detect bone structure defects as small as 0.1 mm. In addition, we propose that our method is able to predict a possible dehiscence in a semicircular canal. In semicircular canal dehiscence (SCD), the bone overlying the superior canal (SC) is partially absent, causing vertigo, autophony, hyperacusis or hearing loss. Diagnosis of SCD is typically based on multi-slice computed tomography (MSCT) images combined with the consideration of clinical signs and symptoms. Recent studies have shown that MSCT tends to overestimate the size of dehiscences and may skew the diagnosis towards dehiscence when a thin bone layer remains. Evaluations of CT scans for clinical application are typically observer based. We developed a method of objectively evaluating the resolution of CT scanners. We did this for 2 types of computed tomography: MSCT, and cone beam computed tomography (CBCT), which have been reported to have a higher resolution for temporal bone scans. For the evaluation and comparison of image accuracy between different CT scanners and protocols, we built a bone cement phantom containing small, well-defined structural defects (diameter, 0.1-0.4 mm). These small inhomogeneities could reliably be detected by comparing the variances of radiodensities of a region of interest (i.e., a region containing a hole) with a homogenous region. The Fligner-Killeen test was used to predict the presence or absence of a hole (p ≥ 0.05). For our second goal, that is, to see how this technique could be applied to the detection of a possible dehiscence in a SC, a cadaveric head specimen was used to create an anatomic model for a borderline SCD; the SC was drilled to the point of translucency. After semi-automatically fitting the location of the canal, our variance-based approach allowed a clear, significant detection of the thin remaining bone layer. Our approach of statistical noise analysis on bone cement phantoms allowed us to distinguish real irregularities from measured image noise or reconstruction errors. We have shown that with computed tomography, an approach comparing radiodensity variance in regions of interest is capable of detecting inhomogeneities down to 0.1 mm (p ≤ 0.0001). Our analysis of data from the cadaveric head specimen demonstrates that this approach can be used to objectively detect thin layers of bone overlying an SC. This should provide the basis for using this approach for a semi-automated, objective detection of SCD.Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology 02/2014; 35(2):329-37. DOI:10.1097/MAO.0000000000000199 · 1.60 Impact Factor
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ABSTRACT: Objectives To review the characteristic symptoms of superior semicircular canal dehiscence, testing and imaging of the disease, and the current treatment and surgical options. Results and Conclusions Symptoms of superior semicircular canal dehiscence (SSCD) include autophony, inner ear conductive hearing loss, Hennebert sign, and sound-induced episodic vertigo and disequilibrium (Tullio phenomenon), among others. Potential etiologies noted for canal dehiscence include possible developmental abnormalities, congenital defects, chronic otitis media with cholesteatoma, fibrous dysplasia, and high-riding jugular bulb. Computed tomography (CT), vestibular evoked myogenic potentials, Valsalva maneuvers, and certain auditory testing may prove useful in the detection and evaluation of dehiscence syndrome. Multislice temporal bone CT examinations are normally performed with fine-cut (0.5- to 0.6-mm) collimation reformatted to the plane of the superior canal such that images are parallel and orthogonal to the plane. For the successful alleviation of auditory and vestibular symptoms, a bony dehiscence can be surgically resurfaced, plugged, or capped through a middle fossa craniotomy or the transmastoid approach. SSCD should only be surgically treated in patients who exhibit clinical manifestations.12/2012; 73(6):365-370. DOI:10.1055/s-0032-1324397
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ABSTRACT: PurposeReview the CT and MR imaging findings in patients with sudden deafness (SD).Journal de Radiologie 12/2009; 90(12):1823-1835. DOI:10.1016/S0221-0363(09)73588-7 · 0.57 Impact Factor