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The diameters of internal jugular veins on the right and left sides were noted .The mean diameter of the right IJV was 8.7mm and left IJV 8.6mm (Table-3), and the difference is not statistically significant. (p>0.05)

Of more relevance for cerebral blood flow, internal jugular venous pressure at the base of the skull was 9.5 (SD 1.2) mmHg during supine rest, and MAP was between 90 and 95 mmHg (Figs. 1 and 2; Table 1). When the head was elevated ∼25 cm above the level of the heart by raising the bed to 40°, internal jugular venous pressure fell to 0.2 (SD 1.0) mmHg, while MAP was between 90 and 100 mmHg and CVP fell from 7.0 (SD 0.5) to 3.0 (SD 1.0) mmHg. While the subjects were sitting up, spinal fluid pressure was 26 (SD 4) mmHg, corresponding to a pressure of 0.1 (SD 4.1) mmHg at the base of the brain. Cerebral blood flow was maintained in the upright position as jugular venous [62.0 (SD 2.4)%] and frontal lobe oxygen saturation [68.4 (SD 1.1)%] did not change significantly.

Schreiber and colleagues[46] also investigated human cerebral venous blood drainage with color-coded duplex ultrasound. In their first study, they reported that total venous blood flow at rest was 766 ± 226 mL/minute in healthy human volunteers in the supine position, with the majority of flow through the internal jugular veins (720 ± 232 mL/minute) and a small amount of flow (47 ± 33mL/ minute) through the vertebral veins.[46] In a later study, they found that 6% of healthy human volunteers had a predominantly nonjugular pattern of cerebral venous drainage when in the supine position.[41]

Cece wrote:www.medscape.org/viewarticle/522597_3

Schreiber and colleagues[46] also investigated human cerebral venous blood drainage with color-coded duplex ultrasound. In their first study, they reported that total venous blood flow at rest was 766 ± 226 mL/minute in healthy human volunteers in the supine position, with the majority of flow through the internal jugular veins (720 ± 232 mL/minute) and a small amount of flow (47 ± 33mL/ minute) through the vertebral veins.[46] In a later study, they found that 6% of healthy human volunteers had a predominantly nonjugular pattern of cerebral venous drainage when in the supine position.[41]

If nonjugular pattern of cerebral venous drainage can be considered akin to CCSVI, this is nearly identical to Dr. Haacke's findings of 8% of healthy volunteers had CCSVI.