Carotid Artery Dissection

A real headache
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Diagnosis and reasoning

Headache is a very common presenting complaint and may be secondary to both benign and sinister causes. Features suggestive of a sinister eitiology include early morning worsening of the headache, worsening with coughing or sneezing, or an acute onset severe headache. While this patient has not manifested any such symptoms, the fact that this is a new onset headache and the progressive worsening of symptoms indicate that further evaluation is required. The examination reveals partial ptosis, miosis and enopthalmos - findings suggestive of Horner's syndrome. Horner's syndrome occurs following damage to the cervical sympathetic pathway. Loss of sympathetic innervation of the superior tarsal muscle leads to partial ptosis, while anhidrosis (decreased sweating of the affected half of the face), enopthalmos (sunken eye) and miosis (pupillary constriction secondary to unopposed parasympathetic innervation) are also seen. The sympathetic outflow arises at the level of T1. From here, the cervical sympathetic trunk ascends upwards, crossing the neck of the first rib and then traveling embedded in the posterior wall of the carotid sheath upto the base of the skull. Horner's syndrome may occur due to a lesion at any point of this course, leading to a wide list of differentials ranging from synringomyelia to pancoast tumors to cervical lymphadenopathy and carotid aneurysms. The diagnosis of painful Horner's syndrome much less broad. Potential causes include cluster headaches, carotid arterial dissection and Raeder's paratrigeminal syndrome. Cluster headaches are usually unilateral, short lasting headaches which are often retro-orbital or peri-orbital. The pain is usually described as sharp or stabbing rather than throbbing and there is often a history of chronic, recurrent headaches. Raeder's paratrigeminal syndrome resembles Horner syndrome in that there is partial ptosis and miosis. However, sweating is preserved while sensory irritation results in both headache and pain in the distribution the ophthalmic division of the trigeminal nerve. Dissection of the carotid artery is classically associated with unilateral pain in the head, face or neck; Horner's syndrome; and retinal or cerebral ischemia. The presence of at least two of these features is strongly suggestive of this diagnosis. The CT scan of his brain demonstrates an area of low attenuation in the right parietal lobe - this is strongly suggestive of an infarction, lending further strength towards a diagnosis of carotid arterial dissection. The Magnetic Resonance Angiogram (MRA) shows an area of stenosis in the Left Internal Carotid Artery (ICA), while the T1 weighted axial image demonstrates an intramural hematoma causing obstruction of L/ICA. Thus the diagnosis is Horner's syndrome and infarction of the left parietal lobe secondary to spontaneous dissection of the L/ICA. He needs immediate anticoagulation with Heparin. Warfarin should be commenced concomitantly, with heparin discontinued once an international normalized ratio (INR) of between 2.0 to 3.0 has been achieved. Given his young age, the underlying etiology is unlikely to be atherosclerotic disease - thus therapy with statins is not indicated. Carotid graft replacement is not indicated currently.


Discussion

Extracranial ICA dissection is an uncommon cause of stroke, accounting for 1% to 2% of all ischemic strokes. However, it is an important cause of stroke in young and middle aged patients (25 to 45 years), with an estimated incidence of between 10% to 25%. While this may be secondary to blunt or penetrating neck trauma, or hyperextension or lateral rotation of the cervical spine (i.e. following yoga or chiropractic neck manipulation), or even just coughing or sneezing, there is often no obvious preceding event. Patients may also have a history of arteriopathy, fibromuscular dysplasia or connective tissue disorders like Ehlers-Danlos syndrome, Marfan's syndrome, autosomal dominant adult polycystic kidney disease, osteogenesis imperfecta or cystic medial necrosis. The classical triad of presentation of extracranial ICA dissection is ipsilateral headache, facial or neck pain and Horner's syndrome, followed hours or days later by cerebral or retinal ischaemia. While the complete triad is found in less than one third of patients, even the presence of just two elements strongly suggests this diagnosis. Other manifestations include syncope, neck swelling, cranial nerve palsies and pulsatile tinnitus. TIAs and cerebral infarctions are found in 20% to 30% and 40% to 60% of patients respectively. Most infarcts are embolic in origin, while the remainder are hemodynamic in origin due to reduced blood flow. Digital Subtraction Angiography (DSA) is the current gold standard for diagnosis, with the most common finding being an eccentric, smooth, or irregularly tapered stenosis of the ICA. Other findings include an intimal flap and associated false lumen, a tapered stenosis proximal to a dissecting aneurysm (also known as the "string-and-pearl sign"), a flame-shaped occlusion, and an intraluminal thrombus. Magnetic Resonance Angiography (MRA) with Magnetic Resonance Imaging (MRI) is a non-invasive alternative to DSA which also provides complementary information about ischemic injury to the brain. CT Angiography (CTA) and Duplex Ultrasonography may also be used for diagnosis. The medical management of spontaneous extracranial ICA dissection centers around antithrombotic therapy, i.e. anticoagulation or antiplatelet therapy. Anticoagulation with heparin has been shown to stop emboli formation. In addition, heparin has further protective effects as it decreases smooth muscle proliferation and platelet aggregation, and may potentially blunt ischemic reperfusion injury. Warfarin therapy should be commenced concomitantly and continued for at least 3 months. Antiplatelet therapy with Asprin and/or Clopidogrel or Dipyridamole has been observed to be of benefit, possibly as the thombi within the ICA are usually "white clots", ie, rich in platelets. Glycoprotein IIb/IIIa inhibitors like Abciximab may also be considered. Similar to anticoagulation, antiplatelet therapy should be continued for at least 3 months. Note that anticoagulation and antiplatelet therapy are usually not used in combination. Current studies suggest that thrombolytic therapy may be considered when ICA dissection is associated with an acute ischemic stroke. Endovascular stenting, coil embolization or therapeutic occlusion is gaining in popularity as a modality of treatment. Surgical intervention is often difficult, with modalities of treatment including ICA ligation or clipping, patch angioplasty, thromboendarterectomy and extracranial to intracranial bypass procedures. The death rate from dissections of the ICA is < 5%, while about three quarters of patients who have a stroke make a good functional recovery. The risk of recurrent dissection is about 2% during the first month but then decreases to about 1% per year. However, this increased risk persists for at least a decade or more.


Take home messages

  1. The diagnosis of painful Horner's syndrome includes ICA dissection, cluster headaches and Raeder's paratrigeminal syndrome.
  2. Extracranial ICA dissection is implicated in 10% to 25% of strokes in young to middle aged patients.
  3. The classical triad of presentation of extracranial ICA dissection is ipsilateral headache, facial or neck pain; Horner's syndrome; and cerebral or retinal ischaemia.
  4. TIAs and cerebral infarctions are common in patients with ICA dissection and are usually due to thromboembolism.
  5. DSA is the current gold standard for diagnosis, although MRA is a safe and acceptable alternative.
  6. The medical management of spontaneous ICA dissection centers around antithrombotic therapy.

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  1. AJNR : Is It Possible to Recognize Cervical Artery Dissection on Stroke Brain MR Imaging? A Matched Case-Control Study (2011)
  2. European Radiology : Carotid and vertebral artery dissections: clinical aspects, imaging features and endovascular treatment (2007)
  3. Journal of stroke and cerebrovascular diseases : Clinical and Radiographic Natural History of Cervical Artery Dissections (2009)
  4. Lancet Neurology : Cervical-artery dissections: predisposing factors, diagnosis, and outcome (2009)
  5. Neurosurgery : Cerebrovascular Dissections - A Review Part I: Spontaneous Dissections (2011)
  6. The open neurology journal : Cervical Artery Dissection: Emerging Risk Factors (2010)