Carotid Artery Dissection

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Learning objectives

  • Understand the aetiology and risk factors
  • Be able to recognise the clinical presentation
  • Discuss diagnostics and treatment strategies
  • Intracranial vs Extracranial (Cervical) artery dissection.

Introduction to Dissection

Cervical artery dissection (CAD) accounts for 10-20% of all strokes in young adults. It is a relatively new diagnosis as the first report of a spontaneous internal carotid artery (ICA) dissection appeared in 1959 [5]. Spontaneous dissections are the leading cause of stroke in patients younger than 45 years of age. It is a diagnosis that must be constantly sought and can easily be missed if the correct imaging tests are not done or delayed. Dissection occurs when there is a tear in the intimal layer of a blood vessel with bleeding and haematoma within the vessel wall. The diagnosis needs to show the presence of a mural haematoma located in the arterial wall. The haematoma may be due to an intimal tear and entry of luminal blood or from vasa vasorum or both. This can lead to overlying thrombus or vessel stenosis or occlusion. The clot can cause complete or subtotal occlusion of the carotid artery or vertebral artery. Damage to the endothelium means that the vessel loses its natural "non-stick-surface" and so clot can form on the luminal intimal surface and cause an artery to artery embolisation which is the rationale for anticoagulation/antithrombotic therapy. There is a small risk that dissections can extend proximally and as intracranial vessels are more fragile when the dissection extends intracranially there is a risk of subarachnoid haemorrhage with typical SAH presentation. This may temper any desire to anticoagulate and as all of this is an evidence light area different clinicians may have different ways to manage these perceived risks. The incidence of cervical artery dissection is estimated at about 2.6-3.0 per 100,000 per year in a North American population. This is likely a true underestimate as cases that have little or no clinical signs are likely to remain undiagnosed especially if uncomplicated by stroke or other clinical issues. Vertebral-artery dissections are slightly less common [4]. The mean affected age is usually adults in their mid-40s. Intracranial artery dissection differs from cervical artery in that it is less common and there is an increased risk specifically of SAH. It is also reportedly more common in children and in Asian populations. The diagnosis can be more challenging because characteristic imaging features can be difficult detect in view of the small size of intracranial arteries. Intracranial artery dissections tends to favour the posterior circulation more frequently than the anterior circulation which contrasts with cervical dissection. Multimodal imaging e.g. CTA/MRA/ and DSA may be needed. A good review is found below[3].

Carotid artery dissection

Always consider this diagnosis in a young adult (under 50) with an anterior circulation stroke unless an alternative cause is evident. Carotid dissection is about 3 times commoner than vertebral. Commonest in those in their mid-40s but seen at any age. This most commonly occurs in the internal carotid artery approximately 2-3 cm after the bifurcation. A very small minority (2%) can be associated with connective tissue diseases such as Marfan's syndrome, Ehlers-Danlos Type IV or Fibromuscular dysplasia. Males and females are equally affected. Pathophysiology is poorly understood but believed to be a mixture of trauma plus an inherent weakness in the vessel. Dissection may be precipitated by accidental neck trauma or cervical manipulation. The trauma may precede the dissection by several hours or days. Clinically the patient usually complains of pain anywhere along the internal carotid artery up into the face and behind the eye. Disruption to the sympathetic supply to the eye which is closely associated with the artery can cause an Ipsilateral Horner's syndrome - mild ptosis, small pupil, enophthalmos, Ipsilateral Stroke findings if embolises or ICA occludes. Rarely dissection extends into intracranial vessels and possibly leads to a thunderclap headache and other SAH symptoms. The investigations of choice is an MRI with fat suppression of the neck which shows crescent-shaped intramural clot and MRI-DWI may show infarction. The vessels and any obstruction can be imaged with MRA. Carotid Doppler may show an intimal flap, haematoma or an occluded vessel.

<img src='http://strokeeducation.co.uk/images/neurodisssection1.jpg'>

Risk factors

  • Mild to moderate trauma - coughing , sneezing or turning head +
  • Chiropractic manipulation
  • Fibromuscular dysplasia
  • Marfan's syndrome
  • Ehlers-Danlos syndrome
  • Tuberous sclerosis
  • Postpartum dissection

Clinical

  • Asymptomatic presenting only as large vessel stroke
  • Neck pain, Facial pain and retro-orbital pain
  • Ipsilateral Horner's syndrome due to damage to sympathetic supply that runs with carotid
  • Migrainous type headache
  • PACI or TACI type stroke due to Carotid occlusion or emboli to MCA
  • Subarachnoid haemorrhage more with intracranial dissections

Investigations

  • Bloods: FBC, U&E, LFT, CRP Others:CXR, ECG
  • Duplex:Carotid duplex: may show an intimal flap and/or occluded carotid
  • CT/MRI : May show infarction or presence of embolised clot in MCA.
  • CTA/MRA: shows the tapering lumen and its location and a possible string sign which is sensitive but not specific for dissection as the cause.
  • Axial T1 MRI with fat suppression which will show a cross section of the artery with intramural blood. This is often done accompanied by the MRA.
  • Above: Left Carotid Dissection</a> The crescentic flap within the left internal carotid artery can be seen on MRI with fat suppression/saturation. This crescent-shaped rim of hyperintense signal adjacent can be matched with a narrowed segment of an artery on angiography. Infarction if it occurs is either embolic or due to complete occlusion of the vessel. There is a more tapered appearance than seen with an embolic or in situ blockage.

<img src='http://strokeeducation.co.uk/images/cardiss.jpg' width=300>

Differentials: Headache + Acute Vascular Neurology

  • Cerebral venous thrombosis
  • Vasculitis
  • Reversible vasoconstriction syndrome

Management

In terms of management, in the acute phase all patients with suspected acute arterial dissection should be considered for thrombolysis. There is no evidence of any increased risk of related haemorrhage[2]. Following the hyperacute period the main therapy is antithrombotic therapy or anticoagulation to reduce the risk of intimal thrombus formation and embolism and to maintain vessel patency. The choice is between Aspirin, clopidogrel and warfarin. There is no evidence base in favour of either[1]. Some give Warfarin for 3-6 months. Others favour aspirin and/or clopidogrel in combination for several months and then long-term anti-platelet therapy for at minimum one year. Choice of therapy depends on whether dissection has been accompanied by a stroke, the size of stroke and risks of haemorrhagic transformation. If the patient presents with an acute stroke then thrombolysis should certainly be considered and carotid dissection is not a contraindication. [2]. Lastly, if an inherent genetic defect is suspected e.g. Ehlers-Danlos syndrome then the patient should be referred to a geneticist. Patients will need standard ongoing rehabilitation and support post stroke. The reoccurrence of dissection is uncommon. In most cases, the natural history is benign and many lesions will spontaneously resolve or remain stable. Follow up imaging of any detected vascular anomalies such as aneurysm formation or to see if there has been recanalisation may be considered if it will change further management. Lastly the management differs slightly in those with intracranial dissections who are at risk of developing SAH with a dissecting aneurysm. These may need a more aggressive endovascular or surgical approach to management. Endovascular or surgical treatment of ruptured dissecting aneurysms seems to offer significant benefit; in a series of ruptured vertebrobasilar dissecting aneurysms, the mortality rate in the treated group was 20%, whereas that in the untreated group was 50% [6].

References and further reading

  • 1. <A href="http://www.thelancet.com/pdfs/journals/laneur/PIIS1474-4422(15)70018-9.pdf"> Antiplatelet treatment compared with anticoagulation treatment for cervical artery dissection (CADISS): a randomised trial The CADISS trial investigators. Lancet Neurol 2015; 14: 361:67</a>
  • 2. Qureshi, AI et al. Thrombolytic Treatment of Patients With Acute Ischemic Stroke Related to Underlying Arterial Dissection in the United States. Arch Neurol. 2011;68(12):1536-1542. Published online August 8, 2011. doi:10.1001/archneurol.2011.213
  • 3. Debette S et al. Epidemiology, pathophysiology, diagnosis, and management of intracranial artery dissection. Lancet Neurol 2015; 14: 640-54
  • 4. Debette S, Leys D. Cervical-artery dissections: predisposing factors, diagnosis, and outcome Lancet Neurol 2009; 8: 668-78
  • 5. Anderson RM, Schechter MM. A case of spontaneous dissecting aneurysm of the internal carotid artery. J Neurol Neurosurg Psychiatry. 1959;22:195-201.
  • 6. Rabinov JD, Hellinger FR, Morris PP, Ogilvy CS, Putman CM. Endovascular management of vertebrobasilar dissecting aneurysms. AJNR Am J Neuroradiol. 2003;24(7):1421-1428.