Dissection of the Carotid and Vertebral Arteries

Overview

Definition

Arterial dissection is a violation of the structural integrity of the arterial wall that results in blood accumulating between the layers.

Epidemiology

• Mean age at onset: 44–46 years.
• Common cause of stroke in young patients
• No clear sex or ethnic predilection
• Carotid artery dissection is more common overall than vertebral artery dissection.
• Combined annual incidence: 2.6 per 100,000

Etiology

• Spontaneous in majority of cases
• Blunt or penetrating trauma:
  • Falls
  • Automobile accidents
  • Minor sport-related injuries
• Chiropractic manipulation: no definitive evidence
• Risk factors:
  • Hypertension
  • Fibromuscular dysplasia
  • Connective tissue disorders:
    • Marfan syndrome
    • Ehlers–Danlos syndrome
  • Oral contraceptives
  • Smoking
  • Infection
  • Migraine
  • Pregnancy

Pathophysiology and Clinical Presentation

Pathophysiology

Dissection formation:

• Dissection results from separation of arterial wall layers.
• A false lumen forms.
• Blood can enter the false lumen through the intimal tear or from the disruption of the vasa vasorum.
• Intramural hematoma results.
• Extension of the false lumen into the true lumen results in a double channel.

Most common locations:

• Extracranial dissections are more common than intracranial.
• Carotid: internal carotid artery 2 cm above carotid bifurcation
• Vertebral: 
  • Cervical transverse processes C2–C6
  • Segment between C2 and foramen magnum
  • Multiple synchronous dissection occurs in 13%–22% of cases.

Pathophysiologic effects:

• Subintimal dissection usually results in vessel stenosis or occlusion.
• Ischemic stroke may result from hypoperfusion or a thromboembolic event (more common).
• Subadventitial dissections result in aneurysm formation.
• Symptoms may arise from an aneurysm compressing adjacent structures and distention of a vessel wall.
• Rarely, dissection of thin intracranial arteries may result in vessel rupture and cerebral hemorrhage.

Clinical presentation

Local symptoms:

• Unilateral head, face, or neck pain
• Pulsatile tinnitus (coincides with pulse; present in 8%)
• Severe occipital pain (vertebral artery)
• Partial Horner syndrome:
  • Present in 25%
  • Distention of sympathetic fibers
  • Miosis and ptosis
  • Usually no anhidrosis, because sympathetic fibers supplying sweat glands follow external carotid artery, whereas dissection usually involves the internal carotid artery.
• Cranial or cervical neuropathies:
  • Affect up to 12% of patients
  • Cranial nerve Ⅻ most commonly involved
  • Cervical nerve root involvement with vertebral artery dissection (rare)

Ischemic symptoms:

• Strokes or transient ischemic attacks (TIAs)
• Carotid artery (anterior circulation stroke symptoms):
  • Contralateral paresis
  • Monocular blindness
  • Upper-extremity paresis
  • Aphasia
  • Ipsilateral facial weakness
• Vertebral artery (vertebrobasilar ischemia):
  • Ipsilateral facial pain and numbness (dysesthesia)
  • Loss of pain and temperature in the ipsilateral face and contralateral trunk/limbs
  • Lateral medullary infarct (Wallenberg) syndrome:
    • Loss of taste
    • Dysphagia
    • Dysarthria
    • Hoarseness (ipsilateral vocal cord paralysis)
    • Vertigo
    • Lack of automatic respiration during sleep
    • Hiccups
    • Ipsilateral Horner syndrome
    • Ipsilateral limb ataxia
  • Cervical cord ischemia

Subarachnoid hemorrhage:

• Rare
• Can result from intracranial artery dissection

Diagnosis

History

• Acute or subacute headache or neck pain
• Neurologic/stroke symptoms
• Recent trauma (even minor) or sports activities
• Intense sneezing/coughing
• Horner syndrome
• History of migraines
• History of connective tissue disorders

Physical exam

• Focal neurologic signs
• Slurred speech
• Ataxia
• Carotid bruit on auscultation

Imaging

• CT angiography (CTA) or MRA is the preferred test:
  • High sensitivity and specificity
  • Characteristic findings:
    • String sign (long stenosis)
    • Tapered stenosis or occlusion or flame-shaped occlusion
    • Intimal flap
    • Dissecting aneurysm
    • Intramural hematoma: crescent sign
    • Distal pouch
• Arterial duplex and transcranial Doppler:
  • Can be used as a screening test or to monitor therapy
  • Relatively low sensitivity
  • Suboptimal yield for identifying dissection near the skull base and vertebral artery dissection within the transverse foramina
• Conventional angiography:
  • Invasive
  • Used when clinical presentation is suggestive of dissection despite negative studies.

Management

Local nonischemic symptoms

• Do not require specific treatment
• Antiplatelet therapy is administered for stroke prevention.

TIA or stroke

• Treatment should follow the same protocol as any ischemic stroke.
• Thrombolytic treatment started only after intracranial hemorrhage is ruled out using noncontrast head CT.
• Acute phase:
  • IV thrombolysis with alteplase is recommended for eligible patients.
  • Time window: 3–4.5 hours after symptom onset
  • Proximal intracranial artery occlusion may also benefit from mechanical thrombectomy up to 24 hours after presentation.
  • Emergency stenting can be performed in experienced centers.
• Beyond the acute period:
  • Anticoagulation or antiplatelet drugs are recommended.
  • Antiplatelet drugs, not anticoagulation, should be used for intracranial dissections to avoid the risk of subarachnoid hemorrhage.
  • Should be delayed until 24 hours after IV thrombolytic therapy
  • Can be started immediately if not treated with IV thrombolytic therapy
• Endovascular surgical repair: indicated only for ischemia that recurs despite medical management

Subarachnoid hemorrhage

• Neurosurgical intervention
• Available methods include:
  • Proximal occlusion
  • Wrapping of pseudoaneurysm
  • Bypass
  • Embolization
  • Stenting

Differential Diagnosis

• Ruptured cerebral aneurysm: Subarachnoid hemorrhage results in a sudden, violent “thunderclap headache.” Diagnosis of an acute hemorrhage can be established with a noncontrast head CT. Treatment of the aneurysm involves neurosurgical vascular interventions such as clipping and embolization.
• Carotid stenosis: chronic atherosclerotic disease resulting in narrowing of the common and internal carotid arteries: Acute presentation involves ischemic stroke or TIA with anterior distribution similar to carotid artery dissection. Diagnosis is established with imaging, and acute treatment is focused on stroke management. Long-term management involves antiplatelet therapy and surgical carotid endarterectomy.
• Vertebrobasilar insufficiency: stenosis of vertebral and basilar arteries secondary to atherosclerosis: Vertebrobasilar insufficiency results in compromised circulation to the posterior brain. Symptoms include dizziness/vertigo, numbness, slurred speech, weakness, confusion, and loss of coordination. Diagnosis can be made with MRA or CTA, and treatment is focused on control of hypertension and cholesterol and lifestyle modifications.
• Migraine: a recurrent headache of varying intensity and characteristics: Migraines can sometimes be accompanied by vision changes, focal neurologic symptoms, photophobia and phonophobia. Diagnosis is clinical, and management can include a variety of therapies, such as NSAIDs, triptans, compazine, caffeine, and oxygen.
• Horner syndrome: disorder characterized by a constricted pupil (miosis), drooping of the upper eyelid (ptosis), absence of sweating of the face (anhidrosis), and sinking of the eyeball into the bony cavity (enophthalmos): Horner syndrome is most commonly caused by apical lung cancer compressing the sympathetic plexus. Internal carotid artery dissection can cause partial Horner syndrome, which is characterized by the absence of anhidrosis.