11/03/2025
Basics of Craniocervical Artery Dissection (CAD) 🧠
👉 The craniocervical artery wall is composed of three distinct layers: the innermost tunica intima, the muscular middle layer called the tunica media, and the outermost tunica adventitia. Craniocervical artery dissection (CAD) occurs when there is an abrupt tear in the tunica intima, leading to blood entering the subintimal space. This results in the vessel wall progressively encroaching into the lumen, causing it to narrow and sometimes completely close off (https://pubmed.ncbi.nlm.nih.gov/32335072/, https://pubmed.ncbi.nlm.nih.gov/32335072/). The dissection site becomes prone to clot formation due to irregular blood flow and the exposure of thrombogenic (clot-promoting ) factors. Additionally, the expanding vessel wall may press on nearby structures, such as cranial nerves (https://pubmed.ncbi.nlm.nih.gov/8614494/). If the intramural hematoma extends into the adventitia, it can form a pseudoaneurysm, and a rupture of this pseudoaneurysm may lead to subarachnoid hemorrhage (SAH) if the dissection involves intracranial blood vessels (https://pubmed.ncbi.nlm.nih.gov/32335072/, https://pubmed.ncbi.nlm.nih.gov/35379423/).
👉 S. figure 1 (https://pubmed.ncbi.nlm.nih.gov/32335072/)
👉 CAD has an annual incidence rate of approximately 3 per 100,000 people, though this figure may underestimate the true occurrence due to cases without symptoms (https://pubmed.ncbi.nlm.nih.gov/17130413/). While relatively rare, CAD accounts for up to 25% of ischemic stroke cases in younger individuals. Over half of CAD instances arise spontaneously, while nearly 90% of trauma-related dissections stem from minor injuries (https://pubmed.ncbi.nlm.nih.gov/23635964/). Connective tissue disorders—such as fibromuscular dysplasia, Ehlers-Danlos, Marfan, and Loeys-Dietz syndromes—are known risk factors (https://pubmed.ncbi.nlm.nih.gov/27511817/, https://pubmed.ncbi.nlm.nih.gov/30739593/, https://pubmed.ncbi.nlm.nih.gov/11259724/). Notably, many CAD patients exhibit subtle connective tissue issues like joint hypermobility, easy bruising, or slow wound healing, hinting that CAD might reflect an unrecognized connective tissue condition (https://pmc.ncbi.nlm.nih.gov/articles/PMC4248452/). Additional factors like recent infections, high blood pressure, oral contraceptives, smoking, pregnancy, migraines, and an elongated styloid process are also linked to CAD, though their exact contribution to its development remains unclear (https://pubmed.ncbi.nlm.nih.gov/19539238/, https://pubmed.ncbi.nlm.nih.gov/32205242/).
✅ Clinical Presentation
👉 CAD patients may experience transient ischemic attacks (TIAs) or acute ischemic strokes due to thromboembolism or arterial occlusion, or SAH from a ruptured dissecting aneurysm in intracranial vessels. Other symptoms include head or neck pain, pulsatile tinnitus, Horner syndrome, cranial nerve compression, and cervical radiculopathy, all stemming from the vessel’s rapid expansion (https://pubmed.ncbi.nlm.nih.gov/35379423/).
✅ Headache or Neck Pain (s. figure 2, https://pubmed.ncbi.nlm.nih.gov/35379423/)
👉 Pain in the head or neck is the most frequent symptom following CAD, affecting 80% of patients, even without SAH. This pain may be vague and widespread, but sudden, severe, and persistent head or neck pain in a young adult should raise suspicion of acute dissection. The pain’s location can indicate the affected vessel: carotid artery dissection may cause one-sided neck, retro-orbital pain or temporal pain, while vertebral artery dissection often leads to pain in the posterior cervical or occipital region (https://pubmed.ncbi.nlm.nih.gov/26757710/). CAD should also be considered in cases of sudden “thunderclap” headaches, hemicrania continua, or trigeminal neuralgia-like pain (https://pubmed.ncbi.nlm.nih.gov/26757710/). In patients with a history of migraines, CAD may intensify their usual headaches.
✅ TIA/Ischemic Stroke
👉 Over 50% of symptomatic CAD patients experience a TIA or acute ischemic stroke (https://pubmed.ncbi.nlm.nih.gov/17130413/). Depending on the dissection’s location and the vessel involved, symptoms might include sudden one-sided weakness, speech difficulties, facial drooping, vision loss or double vision, balance problems, or a mix of these (https://pubmed.ncbi.nlm.nih.gov/17130413/). CAD should always be suspected in young stroke patients.
✅ Subarachnoid Hemorrhage
👉 A sudden, intense “thunderclap” headache—peaking within seconds—with or without altered consciousness or neurological deficits, warrants urgent evaluation for SAH caused by a ruptured dissecting aneurysm (https://pubmed.ncbi.nlm.nih.gov/35379423/). This is more common in intracranial CAD, particularly in the distal vertebral artery.
✅ Other Effects of Compression in CAD
👉 Up to 25% of CAD patients may show partial Horner syndrome-drooping eyelid and small pupil without sweating changes- due to pressure on sympathetic fibers in the carotid sheath. About 8% report one-sided pulsatile tinnitus (https://pubmed.ncbi.nlm.nih.gov/27120261/). Cranial nerve issues (affecting nerves 3 through 12) can occur, with tongue weakness from hypoglossal nerve palsy being the most common (https://pubmed.ncbi.nlm.nih.gov/8614494/). Tongue movement should thus be checked in suspected cases. Though uncommon, CAD may also cause one-sided nerve root compression in the neck, most often at the C5-C6 level (https://pubmed.ncbi.nlm.nih.gov/10908913/).
