FLEX January 2024

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Z. Liu et al. / Clinical Radiology 70 (2015) 943 e 947

signi fi cant difference in the prevalence of SSCD among the PT ears, non-PT ears in the PT group, and controls ( p < 0.0001). The prevalence of SSCD in PT ears was signi fi cantly higher compared with controls and non-PT ears in the PT group ( p < 0.0001 and p ¼ 0.014, respectively); how ever, the prevalence of SSCD was not statistically different when comparing non-PT ears in the PT group with controls ( p ¼ 0.043 < 0.017). Based on the DP-CECT images, 15 PT ears and two non-PT ears were identi fi ed as type II SSCD (Fig 1). Type I SSCD was seen in six PT ears and 13 non-PT ears (Fig 2). The preva lence of type I and type II SSCD was signi fi cantly different between PT ears in the PT group and non-PT ears in both groups ( p < 0.0001). The prevalence of type II SSCD in PT ears was 3.7%, which was signi fi cantly higher than that of non PT ears (0.1%), and the prevalence of type I SSCD in PT and non-PT ears was similar (1.5% and 0.9%, respectively). The aim of the present study was to evaluate the different imaging characteristics of SSCD with and without PT. The data show the prevalence of type II SSCD in PT ears was signi fi cantly higher than that in non-PT ears in both the PT group and controls, and the prevalence of type I SSCD was similar among the PT ears and non-PT ears, which suggest that SSCD induces PT only when the superior petrosal sinus runs through the dehiscence site. In another words, the su perior petrosal sinus running through the dehiscence may be the essential condition for SSCD to induce PT. The pathological mechanism of SSCD in PT remains unclear 1,7 e 15 . The present fi ndings imply that there may be a causal relationship between type II SSCD and PT, which suggest the pulsation of the superior petrosal sinus would be transmitted to the cochlea through the damaged cortical plate of the superior semicircular canal, inducing pressure Discussion

fl uctuations in the cochlear lymph stimulating the spiral organ and converting the pulse into neural impulses that are experienced as PT. For type I SSCD ears, no pulsation is generated in the cochlear because the superior petrosal si nus is far from the dehiscence. For type II SSCD in non-PT ears, vessel pulsation may be too small to stimulate the spiral organ and induce PT. Although researchers debate whether SSCD is a devel opmental or congenital anomaly 11,18 , all cases developed PT in late middle age in the present study, suggesting that congenital type II SSCD is unlikely. Furthermore, dehiscence in all type II SSCD cases is proximal to the superior petrosal sinus suggesting that dehiscence may be caused by chronic forceful fl ow against the bony plate of the superior semi circular canal leading to gradual thinning of the cortical plate and eventual bony defect formation. The prevalence of the superior petrosal sinus running through dehiscence of the superior semicircular canal in PT ears in the present study was 3.7% (15/408). DP-CECT was used as the primary and initial survey method for radiological investigation in patients with PT at our institution (Neuroradiology Division, Department of Radiology, Emory University School of Medicine, Atlanta). Compared with combined CT angiography and venography with 100 ml contrast medium injected at 3 e 4 ml/s and a fi xed delay of 25 s using contemporary multisection CT, 28 DP-CECT not only has the advantage of demonstrating arterial, venous, skull base, and middle-ear diseases in a single study, but the arterial phase CT is an effective screening tool for dural arteriovenous fi stula. CT images reconstructed with bone algorithms best identify the su perior petrosal sinus running through dehiscence in the superior semicircular canal in the venous phase, which can simultaneously clearly demonstrate the integrity of the cortical roof of the superior semicircular canal and the course of the superior petrosal sinus.

Figure 1 CT images of a 53-year-old female patient with type II SSCD who experienced left-sided PT for 5 months. (a) Axial and (b) oblique sagittal CT images of the bony window show type II SSCD (arrow).

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