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A 23 year-old woman developed left sided headaches after a minor car accident. She had pain in the left neck and a Horner's sign on the left. |
| Carotid Artery Dissection: (Left and Middle) Axial fat suppression
MRIs of the lower
brainstem; (Right) intracranial MRA. Note the bright
signal in the left internal carotid area. The bright signal is
blood, indicating a dissection of the carotid artery. In contrast, note the
normal flow void in the left internal carotid artery (black signal
in the left internal artery). On the MRA, note that the
artery is narrowed by the dissection. Due to collateral
flow at the circle of Willis, dissections do not usually cause strokes by lack of
blood flow, but rather from emboli that travel downstream and occlude the MCA, ACA or one of their branches.
If the diagnosis of dissection is suspected, fat-suppression MRI is
the imaging study of choice. Intramural blood can be well
demonstrated on these scans. Routine magnetic resonance angiography
(MRA) will often demonstrate narrowing or occlusion of the vessel,
but in most cases cannot differentiate dissection from other
etiologies. It is critical to detect a dissection before ischemia
occurs, so that treatment can be promptly initiated.
Arterial dissection occurs due to a tear in the intimal layer of the artery. The tear allows blood to enter the wall and form an intramural hematoma. Depending on which layer of the blood vessel is involved, either a subintimal or a subadventitial hematoma develops. A subintimal hematoma tends to cause stenosis of the artery, whereas a subadventitial hematoma often results in aneurysmal dilatation of the artery. In the case of stenosis, sluggish blood flow distal to the dissection results in the formation of fibrin clot. The clot continues to enlarge and eventually breaks off to travel and dislodge downstream as an embolus. Although rare in the general population, dissections of the carotid and vertebral arteries account for a substantial number of strokes in young adults and middle-aged patients. Most dissections involve some type of trauma or stretch to the head or neck. Sometimes, the trauma is trivial and forgotten by the patient. There is a higher incidence in certain congenital connective tissue disorders, including Marfan's syndrome, cystic medial necrosis, and fibromuscular dysplasia. The recognition of an arterial dissection requires a high degree of clinical suspicion and an ability to recognize some key neurological signs which help to key in on the diagnosis. The classic symptoms and signs of carotid artery dissection include the following: • Pain or headache on one side of the
head, face or neck |
Revised
11/30/06
Copyrighted 2006. David C Preston