Vertebral artery dissection, like arterial dissection elsewhere, is a result of blood entering the media through a tear in the intima. It is potentially lethal and can be difficult to diagnose clinically and radiologically.
Patients present variably, most frequently with neck pain and headache as well as posterior fossa ischaemic events (e.g. TIA or stroke). Other presentations include spinal cord infarction, subarachnoid haemorrhage (SAH) and even cervical nerve root impairment) 1.
As with other arterial dissections, blood enters the wall of the artery through a tear in the intima, and dissects along the intima-media plane. As the blood expands the wall, it compromises the lumen resulting in stenosis or occlusion.
Antecedent blunt trauma is most common, although spontaneous dissections are not uncommon, and may be associated with
- fibromuscular dysplasia (FMD)
- connective tissue diseases 2
Other associations include
- antecedent neck manipulation 5
It is important to note that in addition to identification of the dissections the next most important feature is to assess whether or not the dissection involves the intradural portion of the vertebral artery (V4).
Vertebral artery dissections can thus be divided into two groups:
- extracranial dissection
- with or without intracranial extension
- typically occur at the C1/2 level (V3) 2-3
- intracranial dissection
- typically arise at the origin of the PICA 3
CTA, MRI and catheter angiography can all be used to detect vertebral artery dissection, and each has pros and cons.
CT and CT angiography (CTA) are often the first investigations obtained. Other than demonstrating posterior fossa ischaemia or subarachnoid haemorrhage, CT may identify an occluded vertebral (hyperdense) or mural thrombus (thickened wall, often with some surrounding stranding). CT may sometimes show a characteristic "double lumen" appearence 5.
CTA additionally can, especially with coronal and sagittal reformats, demonstrate irregularity of the lumen, as well as make thickening of the arterial wall more easily appreciable.
In addition to far greater sensitivity to small foci of ischaemia (using DWI), and the ability to image the vessel lumen (MRA), MRI is also more sensitive at imaging intramural haemorrhage. Fat saturated T1 axial images through the neck are best, demonstrating a sickle shaped hyperintensity in the wall of the affected vessel (crescent sign).
Conventional angiography is traditionally considered the gold standard. It may demonstrate focal dilatation, proximal or distal stenosis, or fusiform aneurysmal dilatation 9.
Treatment and prognosis
Both treatment and prognosis are strongly affected by whether or not the dissection extends into the intracranial compartment. If the latter is true, then there is a high rate of subarachnoid haemorrhage, usually with disastrous outcome.
Factors predicting outcome include:
- intracranial extension: subarachnoid haemorrhage
- size of contralateral vertebral artery
- presence and size of posterior communicating arteries and P1 segment of the posterior cerebral artery: collateral flow
- size of posterior fossa ischaemia
Treatment is also largely influenced by location of the dissection. In dissections limited to the extracranial vertebral artery then antiplatelet agents are the mainstay of treatment, aimed at preventing artery-to-artery embolisation and posterior circulation infarcts 3.
Patients with intracranial extension are not treated with anticoagulation or antiplatelet agents on account of the risk of subarachnoid haemorrhage 3. Provided there is adequate collateral flow (i.e large contralateral vertebral artery, intact circle of Willis), and especially in cases of subarachnoid haemorrhage, consideration should be given to operative or endovascular trapping or coiling of the dissected artery 4. Depending on the arterial anatomy, the risk or resulting posterior fossa ischaemia is variable.
Recognised complications include
- arterial thrombosis and occlusion
- embolic infarcts
- dissection-induced stenosis 8
- pseudoaneurysm formation 8
- 1. Baumgartner RW. Handbook on cerebral artery dissection. S Karger Ag. (2005) ISBN:3805579861. Read it at Google Books - Find it at Amazon
- 2. Dickman CA, Spetzler RF, Sonntag VK. Surgery of the craniovertebral junction. George Thieme Verlag. (1998) ISBN:0865776814. Read it at Google Books - Find it at Amazon
- 3. Mohr JP, Grotta JC. Stroke, pathophysiology, diagnosis, and management. Elsevier Health Sciences. (2004) ISBN:0443066000. Read it at Google Books - Find it at Amazon
- 4. Laakso A, Hernesniemi J, Yonekawa Y. Surgical Management of Cerebrovascular Disease. Springer Verlag. (2010) ISBN:321199372X. Read it at Google Books - Find it at Amazon
- 5. Soper JR, Parker GD, Hallinan JM. Vertebral artery dissection diagnosed with CT. AJNR Am J Neuroradiol. 1995;16 (4): 952-4. AJNR Am J Neuroradiol (abstract) - Pubmed citation
- 6. Pelkonen O, Tikkakoski T, Pyhtinen J et-al. Cerebral CT and MRI findings in cervicocephalic artery dissection. Acta Radiol. 2004;45 (3): 259-65. Acta Radiol (link) - Pubmed citation
- 7. Lévy C, Laissy JP, Raveau V et-al. Carotid and vertebral artery dissections: three-dimensional time-of-flight MR angiography and MR imaging versus conventional angiography. Radiology. 1994;190 (1): 97-103. Radiology (abstract) - Pubmed citation
- 8. Ahn JY, Han IB, Kim TG et-al. Endovascular treatment of intracranial vertebral artery dissections with stent placement or stent-assisted coiling. AJNR Am J Neuroradiol. 2006;27 (7): 1514-20. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 9. Shin JH, Suh DC, Choi CG et-al. Vertebral artery dissection: spectrum of imaging findings with emphasis on angiography and correlation with clinical presentation. Radiographics. 20 (6): 1687-96. Radiographics (full text) - Pubmed citation
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