Presentation
2 weeks prior to presentation had neck manipulated by a physiotherapist. Ongoing right-sided neck pain and headache. Now right ptosis and miosis on examination (Horner syndrome).
Patient Data
Absent flow void in the right intracavernous ICA with a cuff of intramural high signal on T1 (methemoglobin) in the distal right ICA at the skull base, consistent with dissection. Note how the right ICA diameter is greater than on the left due to this methemoglobin. Absent right ICA on the TOF MRA with a methemoglobin high signal cuff on the source image (2nd and 3rd images from the right). Right ICA branches (ACA and MCA fill via the circle of Willis).
CTA undertaken to determine...
CTA undertaken to determine extent of carotid dissection
CTA shows the typical tapered appearance to the right ICA just distal to its origin. Note the residual patent ICA true lumen to the skull base "string sign" (arrows), showing that contrast angiography (CTA, catheter angiography or even contrast-enhanced MRA) is more sensitive than the flow-related angiography of TOF MRA.
Case Discussion
Internal carotid artery dissection is a relatively common cause of Horner syndrome. The cervical sympathetic chain accompanies the internal carotid artery in the neck and continues into the skull base via the carotid canal. Rapid expansion in carotid size that occurs due to intramural bleeding in dissection causes the sympathetic chain to be compressed, especially in the carotid canal, leading to a neuropraxia, i.e. Horner syndrome.
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