A striking X-ray image shows the dark threads of arteries and veins carrying blood from wrist to fingertip — except in the index finger, which glows with a ghostly white hue.

The image is an angiogram — a type of medical imaging technique that reveals veins and arteries after they have been flooded with a special dye. If blood is flowing properly, it carries the dye through the branching networks of blood vessels, which show up as dark lines in the image.

The angiogram — which was taken back in 2005 but recently resurfaced on social media — revealed a lack of blood flow in the right index finger of David Schulte, aka Dazzling Dave, a profession yo-yo performer.

So, what led to that unusual image?…