Abstract
Accurate diagnosis of subtypes of transverse sinus (TS) hypoplasia requires more expensive methods like magnetic resonance (MR) imaging. We hypothesized ultrasound findings of the internal jugular vein (IJV) can be surrogate indicators for diagnosis of TS hypoplasia. MR images were reviewed in 131 subjects to evaluate TS diameter and the location and degree of venous flow stenosis and obstruction. Ultrasound parameters including the cross-sectional lumen area (CSA), time-average-mean velocity (TAMV), and flow volume (FV) at each IJV segment were also evaluated. Sixty-nine subjects had TS hypoplasia based on MRV criteria, of which 39 TS hypoplasia were considered a subtype of TS hypoplasia, which is secondary to the downstream venous compression/stenosis or left brachiocephalic vein. In the ultrasound study, the CSA of the IJV ipsilateral to TS hypoplasia was significantly smaller. Further, a contralateral/ipsilateral IJV CSA ratio >1.55 provided good sensitivity, specificity, and positive predictive value for discriminating TS hypoplasia.
Highlights
Asymmetry of the transverse sinus (TS) is a common finding with unilateral hypoplasia or aplasia in 20–39% of cases, and was previously considered to be a normal anatomical variation [1,2,3]
While anatomical TS hypoplasia is associated with TS diameter conformance, flow-related TS hypoplasia only appears on magnetic resonance venography (MRV) due to downstream internal jugular vein (IJV) or brachiocephalic vein (BCV) compression/stenosis, and has been associated with neurological disorders of venous outflow impairment [8,9,10]
The detailed distribution of subjects with and without TS hypoplasia was reported in Table 1 of our previous paper [10]
Summary
Asymmetry of the transverse sinus (TS) is a common finding with unilateral hypoplasia or aplasia in 20–39% of cases, and was previously considered to be a normal anatomical variation [1,2,3]. Two types of TS hypoplasia (anatomical TS hypoplasia and flow-related TS hypoplasia) were recently distinguished using a post-hoc analysis of the discrepancy and conformance of TS diameters measured by MRV and contrast T1 [10]. While anatomical TS hypoplasia is associated with TS diameter conformance, flow-related TS hypoplasia only appears on MRV due to downstream internal jugular vein (IJV) or brachiocephalic vein (BCV) compression/stenosis, and has been associated with neurological disorders of venous outflow impairment [8,9,10]. Previous TS hypoplasia studies reporting adverse neurological effects included both the anatomical TS hypoplasia and flow-related TS hypoplasia and did not pay attention to the outflow impairment [4,5,6,7]. A simple non-invasive test of physiological flow variables is necessary to replace more expensive MR imaging studies with contrast or invasive angiography for TS hypoplasia visualization and diagnosis in routine clinical practice
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