CONTENTS

• Pathophysiology
• Epidemiology
• Clinical presentations
  • Manifestations of internal carotid dissection
  • Manifestations of vertebral dissection
  • Overt trauma complicated by cervical artery dissection
• Imaging
• Management
• Podcast
• Questions & discussion
• Pitfalls

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pathophysiology

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arterial dissection may begin in two ways:

• (#1) The true lumen may dissect into the arterial wall. This creates a true lumen and a false lumen (e.g., figure below, panel D).
• (#2) An arteriole may hemorrhage within the arterial wall, creating a self-contained intramural hematoma within the arterial wall (a hematoma that doesn't communicate at all with the artery)(e.g., figure below, panel B).
  • Diagnosis of an intramural hematoma may be difficult, because small hematomas may have no major impact on the lumen anatomy (as visualized by angiography).
• Theoretically, dissection into the arterial wall (panel D) would pose a risk of artery-to-artery emboli, whereas an isolated mural thrombus (panel B) would pose no risk of downstream embolic stroke. Thus, anticoagulation theoretically would be more important for patients with intimal dissection. In practice, imaging modalities aren't yet able to reliably differentiate these types of dissection – so all patients should be anticoagulated if possible.
• The false lumen may rupture outwards. Extracranial arteries have a thick external elastic lamina, so this tends not to happen. However, if the dissection propagates intracranially, the external elastic lamina is thinner so rupture is more likely – which may cause a subarachnoid hemorrhage.(33320488)

potential clinical consequences of dissection

• (i) Impaired flow through the carotid/vertebral artery:
  • A hematoma or false lumen may compress the true lumen of the artery. This may cause a stenosis with reduced flow (e.g., above figure, panel B).
  • Rarely, the artery may become completely occluded (e.g., above figure, panel C). Depending on collateral blood supply within the Circle of Willis, this may cause a catastrophically large ischemic stroke.
• (ii) Clots may form within turbulent blood within the false lumen (e.g., above figure, panel D). These clots may subsequently exit into the true lumen and travel downstream, causing artery-to-artery embolic strokes. This may lead to a pattern of multifocal infarction involving a single vascular territory.
  • Thromboembolism is the cause of most strokes (rather than occlusion of the carotid or vertebral artery itself).(28987426)
• (iii) Pseudoaneurysm formation may occur if blood dissects into the space between the media and the intima (figure below, lower panel). This may increase the outer diameter of the vessel and compress nearby structures:
  • Carotid pseudoaneurysm may compress nearby nerves, causing Horner's syndrome.
  • Vertebral pseudoaneurysm may compress nearby spinal nerve roots, causing radicular pain.

more common sites of dissection

• Carotid dissection most commonly occurs at least 2 cm distal to the bifurcation of the common and internal carotid. The dissection may extend superiorly, but generally stops prior to entering the the skull.(Mohr, 2022)

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epidemiology

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general comments

• Cervical arterial dissections cause ~2% of all ischemic strokes.(28987426)
• Dissection is an important cause of stroke in younger patients (e.g., causing roughly 15% of strokes among patients <45 years old).
• Multiple dissections may occur simultaneously (e.g., bilateral vertebral artery dissections).

underlying etiologies

• Most patients have no known underlying disorder.
• Occasional patients have an underlying connective tissue disorder, for example:
  • Ehlers-Danlos syndrome type IV.
  • Marfan syndrome.
  • Osteogenesis imperfecta.
  • Fibromuscular dysplasia.
  • Autosomal dominant polycystic kidney disease.

potential triggers

• (1) Minor trauma: History often elicits precipitating events, which may seem minor:
  • Painting a ceiling (vertebral dissection).
  • Chiropractic manipulation.
  • Dancing with vigorous head movements (e.g., headbanging).
  • Whiplash from minor car accident.
  • Minor sports injuries.
  • Intentional neck cracking.
  • Severe coughing, sneezing, or vomiting.
  • Childbirth.
  • Roller coaster or amusement park rides.
  • (Essentially any form of neck trauma.)(35506728)
• (2) Overt trauma – see section below. 📖

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manifestations of internal carotid dissection

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unilateral pain

• Pain may involve the neck, face, orbit, frontal, or temporal areas. Headache is present in most patients, but neck pain is absent in ~80% of patients.
• Pain onset is usually gradual, but there may be sudden onset (e.g., thunderclap headache).
• Pain is usually the first symptom, with a median delay of four days until additional symptoms occur.

cerebral or retinal ischemia

• Transient ischemic attack involving the brain or retina (amaurosis fugax) may be a harbinger of subsequent ischemic events.
• Common manifestations of ischemia in the anterior cerebral artery (ACA) and/or middle cerebral artery (MCA) territories may include aphasia, dysarthria, hemiparesis, hemisensory loss, or gaze deviation.

other potential manifestations

• Partial Horner's syndrome: 📖 Ptosis and miosis occur in ~40% of patients, but without anhidrosis (sweat gland innervation follows the external carotid).(35506728) In practice anhidrosis is often difficult to evaluate, so this may be largely indistinguishable from a complete Horner's syndrome.
• Cranial nerve palsies occur in ~10% of patients (especially the hypoglossal nerve; may cause dysgeusia).
• Pulsatile tinnitus occurs in ~15% of patients.

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manifestations of vertebral artery dissection

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headache in most patients

• Pain usually involves the occipital area, but may also cause posterior neck pain.
• Pain is usually unilateral.
• The quality may be variable (e.g., throbbing or sharp).

posterior circulation ischemia

• Ischemic features occur an average of two weeks after the onset of pain.(Wijdicks, 2019)
• Symptoms of posterior ischemia may include vertigo, ataxia, nystagmus, hemiplegia, and cranial nerve abnormalities.
• Ischemia may involve the lateral medulla, causing Wallenberg's syndrome.📖
• Horner's syndrome 📖 may result from brainstem ischemia (although with a frequency of 13%, this is less frequent than with carotid artery dissections).(35506728)

other potential manifestations

• Compression of nerve roots causing cervical radicular nerve pain or palsies (especially C5-C6, which may cause arm weakness and/or numbness along the lateral arm and hand).(33320488)
• Extension of the dissection intracranially may lead to subarachnoid hemorrhage.

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overt trauma complicated by cervical artery dissection

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epidemiology

• Cervical artery dissections occur in ~1% of patients admitted for blunt trauma. (33320488) Carotid artery dissection is more common than vertebral dissection.
• Some examples of trauma which may be complicated by cervical dissection:
  • Motor vehicle crash.
  • Falls.
  • Fractures involving the skull base.
  • Direct trauma to the neck.

clinical presentation

• Initial presentation is often dominated by other traumatic injuries.
• There is usually a lag of 2-3 days before the onset of symptoms due to cervical artery dissection.

indications to consider screening for blunt cervical artery dissection (33320488; 33896528)

• Physical examination signs:
  • Neurologic deficit unexplained by brain imaging, for example:
    • Lateralizing neurologic deficit.
    • GCS <8 without significant CT findings.
  • Neck hematoma.
  • Massive epistaxis.
  • Anisocoria or Horner's syndrome.
  • Cervical bruit or thrill.
  • Neck soft-tissue injury (seatbelt sign or evidence of hanging).
• Imaging findings:
  • Cervical spine fracture (especially involving subluxation or rotational component).
  • Basilar skull fracture (especially involving the carotid canal).
  • Severe facial fracture (e.g., LeFort II or III, mandible fracture).
  • Brain infarction on CT scan.
  • Penetrating brain injury, especially with transverse object trajectories.
  • Diffuse axonal injury with GCS ≤6.

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imaging

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Below are some general concepts regarding the imaging diagnosis of arterial dissection. However, test performance may vary depending on the image quality of any individual study. Furthermore, different tests may be optimal to address different clinical questions (e.g., MRI may be well suited to look for a dissection while simultaneously evaluating the nature of a focal neurological deficit). Given variable data in the literature regarding sensitivity and specificity of these tests, consultation with a radiologist may be helpful to determine the optimal modality and protocol for an individual patient.

carotid ultrasonography

• Potential findings:(28987426)
  • Direct visualization of an intimal flap.
  • Detection of a mural hematoma as a thickened, hypoechoic wall or an increase in the external caliber of the artery.
• Carotid ultrasonography has limited performance due to difficulty visualizing small mural hematomas, or pathology above the angle of the mandible.
• Uses for carotid ultrasonography may include:
  • (1) Screening test, especially in patients who are too unstable for transportation.
  • (2) Serial ultrasonography may be useful to track the progress of a known dissection.

CT angiography (CTA)

• CT angiography is often recommended as an initial study to evaluate for dissection. Compared to MRI/MRA, CTA is often more widely available and more rapidly performed.(35506728)
• CT angiography has excellent performance, with sensitivity and specificity in the range of 98% (although performance among individual patients may vary depending on the exact pathology, scan quality, and reader).(33320488) CT angiography may reveal intimal flaps and vertebral artery dissections better than MRI/MRA.
• CT angiography is not adept at the detection of acute ischemic strokes (especially within the posterior fossa), so if this is a concern then a follow-up MRI +/- MRA is needed.
• 💡 Remember that modern contrast dye is not nephrotoxic.📖

MRI/MR angiography (MRI/MRA)

• MRI/MRA allows for evaluation of the arteries, as well as evaluation of any downstream ischemic stroke (with high-resolution imaging of the brain that includes diffusion-weighted imaging). This is an excellent study to obtain in patients with neurological deficits.
• However, sensitivity and specificity for dissection are variable in the literature (and far from perfect). Sensitivity for vertebral artery dissections may be as low as 20%.(33320488)
• GRE/SWI sequences may be useful if there is concern for possible subarachnoid hemorrhage.

invasive angiography

• Angiography looks only at the vessel lumen (lumenogram), leading to certain limitations:
  • May miss small hematomas or false lumens.
  • May miss features such as an intimal flap or double lumen.(28987426)
• Other limitations of invasive angiography are that it is invasive and has limited availability (especially on an emergent basis).
• The main role for invasive angiography is as a potential therapeutic modality, rather than a diagnostic one (more on this below).

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management

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initial questions to consider:

• Is there additional associated pathology:
  • Pseudoaneurysm?
  • Hemorrhage?
  • Acute ischemic stroke?
• Does the dissection extent past the dura? (This increases the risk for subarachnoid hemorrhage.)(28634505)

management of acute ischemic stroke (superimposed on dissection)

• This generally follows the same principles as for other causes of acute ischemic stroke.
  • ⚠️ Activate the stroke team.
• Dissection is not a contraindication to thrombolysis (unless there is frank rupture of a cervical artery or intercurrent subarachnoid hemorrhage – which are both very rare). Decisions regarding thrombolysis should be deferred to the stroke neurology team.
• Endovascular therapy for large vessel occlusions (LVO) may be possible, with similar outcomes compared to isolated large vessel occlusions.

antiplatelet or anticoagulation medications to prevent stroke

• Most dissections will heal over time, so the primary concern is often prevention of artery-to-artery embolic stroke.
• Stroke prevention may be achieved with anticoagulation (e.g., heparin with subsequent transition to warfarin) or an antiplatelet agent (e.g., aspirin or clopidogrel).
• Some form of anticoagulation (either heparin or aspirin) reduces the risk of stroke from very roughly ~30% to ~3%, so this is extremely important.(33320488)
• Treatment duration is often ~3-6 months, although this remains controversial.(35506728)

choice of antiplatelet agent versus heparin

• The most notable evidence:
  • The CADISS trial randomized 250 patients with cervical artery dissection to antiplatelet therapy versus anticoagulation (heparin followed by warfarin) for three months. No difference was found in endpoints, because the rate of stroke was extremely low in both groups (1-2%).
  • The TREAT-CAD trial randomized 194 patients to aspirin versus anticoagulation. Seven patients in the aspirin group developed ischemic strokes, compared to none in the anticoagulation group (p = 0.02).
• Overall, the choice of antiplatelet agent versus anticoagulation remains debatable. Both are viable therapies. The choice of therapy may depend on the specifics of any individual patient (depending on factors listed below). If all else is equal, anticoagulation might be preferable.
• Factors favoring antiplatelet therapy:
  • Patient has another indication for antiplatelet therapy.
  • Antiplatelet therapy is less expensive and doesn't require monitoring (e.g., aspirin is available over the counter).
  • Aspirin carries a lower risk of hemorrhage. This may be beneficial in patients at increased risk for bleeding, for example:
    • Large territory ischemic stroke with concern for hemorrhagic transformation.
    • Polytraumatized patient with numerous other injuries.
    • Extension of the dissection to involve the intracranial arteries (which carries a risk of subarachnoid hemorrhage).
• Factors favoring anticoagulation:
  • Patient has another indication for anticoagulation.
  • Heparin infusion may be stopped rapidly, if this is important (e.g., in a patient with other traumatic injuries who is at risk of hemorrhage).
  • Heparin might be favored in patients with a mobile thrombus seen in an arterial lumen.(31559486)

endovascular or surgical repair of the dissection

• Endovascular interventions may include stenting (to maintain the patency of the true lumen) and/or coil occlusion of a hematoma.
• Potential indications for endovascular therapy include:
  • Management of a large vessel occlusion (LVO).
  • Recurrent strokes despite medical therapy.
  • Severe occlusion or luminal narrowing.
  • Significantly compromised cerebral blood flow.
  • Enlarging pseudoaneurysm.
• Stent placement will obligate the patient to receive dual antiplatelet therapy. This may be contraindicated in patients unable to tolerate dual antiplatelet therapy (e.g., a polytraumatized patient with numerous pending surgical procedures).(Kumar, 2018)
• Available patient series suggest that endovascular intervention is safe and effective. However, long-term risks of in-stent thrombosis or stent fracture are unclear.(31559486)
• Surgical repair is an alternative strategy, depending on resource availability and patient anatomy. However, many patients have underlying vasculopathy (e.g., Ehlers-Danlos Syndrome), which may increase the risk of surgical complications.

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questions & discussion

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To keep this page small and fast, questions & discussion about this post can be found on another page here.

• Failure to consider the possibility of cervical artery dissection in a patient with additional traumatic injuries.
• Incorrect belief that a cervical artery dissection obligates patients to receive a heparin infusion. Although heparin is often an excellent option, some patients may be better served with antiplatelet therapy instead.

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