Case of the week 3 part 3

The top images show normal density basilar (left) and middle cerebral arteries (right). The bottom left image shows the culprit - a hyperdense right vertebral artery. Acute thrombosis was confirmed with CTA of the head (bottom right, red arrow).

Don't be dissuaded by the trauma history. The vertebral artery corresponds to symptoms of dizziness and vertigo. In this case, the right vertebral artery measured 64 HU, the basilar artery measured 50 HU, and the MCAs measured 42-43 HU.

‍Companion case
This last case shows images from a non-contrast head CT performed in an 84 year old man who was found unresponsive.

The top images show a hyperdense basilar artery (left, 57 HU) contrasted with a normal density left MCA (right, 37 HU). The subsequent two images show the hyperdense basilar artery in the coronal view (middle left) with an acute infarct of the right superior cerebellum (middle right). The final two images confirm basilar artery thrombosis on CTA.

‍Final comments
Accurately diagnosing intra-cranial vessel thrombosis can be difficult. Here are the key points:

• Ensure that the intracranial vessels are in your search pattern. Use a template.
• Stroke symptoms should correspond to the distribution of the hyperdense vessel.
• Compare the density of the middle cerebral, basilar, and vertebral arteries. A hyperdense vessel is typically 12-18 HU greater than the other vessels.
• Patent vessels are typically 30-40 HU, whereas thrombosed vessels are typically 45-68 HU.
• A calcification in an intracranial vessel is not always atherosclerotic calcification. It may be a calcified embolus. Recommend CTA to differentiate these possibilities.
• Always compare to prior imaging. If the vessel was hyperdense before, then it's not acute and not amenable to treatment.
• If the only history you have is "stroke", call the ordering provider and ask about the stroke symptoms.