Board Review 3 – Case 18

Neuroradiology board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.

More description and the answer (spoiler!) are seen below the video.

This case shows a patient with Horner’s syndrome who has subtle narrowing of the extracranial internal carotid artery on the left. On T1 fat-saturated imaging, there is a crescent of methemoglobin within the medial aspect of the vessel wall.

The diagnosis is: internal carotid artery dissection

Anytime a patient, particularly a young patient, has acute onset of neurologic symptoms, arterial dissection has to be on the differential. When it is accompanied by a Horner’s syndrome, internal carotid dissection is high on the differential because the sympathetic fibers for they eye travel alongside the carotid artery.

Arterial dissection is injury to the walls of the vessel. Most often the innermost layer, the intima, is separated from the deeper layers, the media and adventitia. It can be associated with a visible flap of lifted intima in the vessel and a portion of the vessel which is not carrying blood, a false lumen. When the vessel is disrupted enough to have visible dilation, this is a pseudoaneurysm.

In this case, the MR angiogram findings are quite subtle, but the key is the T1 fat-saturated images, which show a crescent of methemoglobin in the vessel wall. Fat saturation is required to differentiate this hyperintensity from the adjacent fat in the neck, which is also hyperintense.

Arterial dissection is associated with a variety of conditions, including trauma, fibromuscular dysplasia, vasculitis, and connective tissue disorders.