|
A 47 year-old man developed the abrupt onset of a left hemiparesis. |
| Carotid Artery Dissection: (Left) Right
Carotid Angiogram at the level of
the carotid bifurcation; (Middle) Right Carotid Angiogram at the level of the
base of the skull; (Right) Axial CT
scan 3 days after presentation. Note on the angiogram the abrupt tapering and occlusion of the
internal carotid artery, forming a "flame" shape. This is one of the classic appearances of a dissection.
Following successful stenting and tPA, circulation was re-established to the
distal carotid artery. Note, however, that the artery remains tapered in addition to the presence
of an aneurysmal sac in the carotid wall. On the CT scan, a hypodensity is seen in the distribution of the right
middle cerebral artery, resulting from an artery to artery embolus from the
dissection. However, without successful opening of the vessel, the size of the
stroke would have been much larger and potentially fatal. CCA = common carotid
artery; ICA = internal carotid artery; ECA = external carotid
artery; MCA = middle cerebral artery. 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 generally rare, dissection of the carotid and vertebral arteries comprises a substantial number of strokes among young adults and middle-aged patients. The recognition of a spontaneous dissection requires a high degree of clinical suspicion and an ability to recognize some key neurological signs which help to hone in on the diagnosis. Dissection is critical to detect before ischemia occurs so that treatment can be initiated promptly. 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 tissues disorders, including Marfan's syndrome, cystic medial necrosis, and fibromuscular dysplasia. In carotid artery dissection, the classic symptoms and signs of carotid dissection may include the following: • Pain or headache on one side of the
head, face or neck Once 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. |
Revised
10/27/06
Copyrighted 2006. David C Preston