Table 1:

Proposed classification of IJV abnormalities on DS

DS Classification	Types/Examples
Intraluminal structural venous abnormality; this is an echogenic structure extending from the endothelial lining of the vein wall with/without presence of functional abnormality; these abnormalities include web, flap, septum, membrane, and malformed valve	Web: multiple septa and/or flaps located in a cluster
	Flap: thin linear echogenic structure extending from endothelial lining of vein wall
	Septum: thin linear echogenic structure extending from endothelial lining of vein wall, and attached to it at both ends; septum may extend across a vein to attach on opposing sides or attach on same side
	Membrane: membranous structure almost occluding the entire diameter of the vein
	Malformed valve: dysdynamic or fibrous valve
Extraluminal structural venous abnormality; this is a restriction of the venous wall or stenosis; these abnormalities include stenosis and annulus	Stenosis: CSA measurement of ≤3 mm²
	Annulus: circumferential thickened vein wall that is restricting the vein from fully expanding with respiratory or positional changes
Functional venous abnormality; this is an abnormal cerebral venous outflow in the presence of a structural venous anomaly; these abnormalities include reflux/bidirectional flow, paradox, and no flow	Reflux/bidirectional flow: present in the IJV for >0.88 seconds with the head at 90° and 0°
	Paradox: vein wall not reacting to respiratory phase; noncompliant
	No flow: no color flow noted in vein, despite deep breaths