Causes of dissection of basilar artery and vertebral artery
Case 140
【Progress】They did not have specific neurological disorders. Then, they were given antihypertension agents. They were scheduled to our hospital for periodic watchful observation to measure blood pressure and get antihypertensives.
【Discussion】
Although it is rare to encounter the dissection of cranio-cervical artery in the daily radiological imaging interpretation on brain MRI, it is important to be familiar with the dissection of carotid artery, vertebral artery and basilar artery. Carotid artery dissection (CAD) is more three to five times more common than vertebral artery dissection (VAD) (1, 2).
Carotid artery dissection (CAD) can be caused by major or minor trauma and by hereditary backgrounds. The age peak of CAD is the fifth decade that indicates it can occur in the youth (1-3). The frequency of CAD is less in intracranial carotid artery than in extracranial carotid artery because skull absorbs external pressure. Intimal tear causes intimal luminal narrowing or pseudoaneurysm. In short, intimal elevation of intima induces luminal narrowing and formation of thrombus causing brain embolism, while tear of not only intima but also adventitia induces hematoma and/or pseudoaneurysm (1-3). CAD is one of the causes for brain embolism in the youth.
Vertebral artery dissection (VAD) is also one of the main cause of the stroke in patients younger than 45 years of age (4, 5). VAD can be caused by major or minor trauma, or from the hereditary backgrounds (2-5). Excessive neck distortion such as chiropractic manipulation or blunt trauma can cause VAD. VAD occurs most in V4 probably arose from V3 which is movable most (V1 = proximal to entry into the transverse foramen of C6, V2 = within the transverse foramen from C2 to C6, V3 = from the transverse foramen of C2 to before entry into the dura, V4 = after entry from the dura to basilar artery) (4, 5). VAD as well as CAD is categorized into ischemic type and hemorrhagic type; ischemic type, luminal stenosis and thrombus formation due to tear of intimal layer: hemorrhagic type, subarachnoid hemorrhage or pseudoaneurysm due to tear of intimal layer, media layer and adventitia layer (4, 5).
Basilar artery dissection (BAD) also manifests subarachnoid hemorrhage and thromboembolism (6, 7). Intimal tear causes occlusive lumen in basilar artery, intimal plus medial tear cause the mural hematoma or pseudoaneurysm and tears of intima plus media plus adventitia cause subarachnoid hemorrhage. BAD occurs at any age and the average age of the occurrence is fourth decade, although the cause is not clarified.
The golden tool of imaging diagnosis for CAD, VAD and BAD is still digital subtraction angiography (DSA) but CT angiography (CTA) is taking place because of the less invasion, followed by MRI and echography (1, 2). Our two patients did not receive DSA and CTA but only MRI because of no symptoms of stroke.
【Summary】
We present two patients with suspicious vertebral artery dissection (VAD) and suspicious basilar artery dissection (BAD). They were not symptomatic and the periodic observation was scheduled in each. As cranio-cervical artery dissections, carotid artery dissection (CAD), VAD and BAD are listed. It is borne in mind that cranio-cervical artery dissections occur in 40 or 50 decades of age, and CAD and VAD can be caused by major or minor trauma, or from the hereditary backgrounds. Chiropractic manipulation causes VAD. VAD occurs most in V4 probably arose from V3 which is movable most. The cause of BAD is still unclarified. The intimal tear induces the occlusive lumen and formation of thromboembolism, inducing brain stroke, the tear of intima and media induce pseudoaneurysm, and the tear of intima, media and adventitia induce hematoma or bleeding (subarachnoid hemorrhage). CT angiography is becoming a golden standard, in taking place of digital subtraction angiography.
【References】
1.Schievink WI. Spontaneous dissection of the carotid and vertebral arteries. N Engl J Med. 2001 Mar 22. 344(12):898-906.
2.Redekop GJ. Extracranial carotid and vertebral artery dissection: a review. Can J Neurol Sci. 2008 May. 35(2):146-152.
3.Goyal MS, Derdeyn CP. The diagnosis and management of supraaortic arterial dissections. Curr Opin Neurol. 2009 Feb. 22(1):80-89.
4.Shin JH, Vertebral Artery Dissection: Spectrum of Imaging Findings with Emphasis on Angiography and Correlation with Clinical Presentation. RadioGraphics 2000; 20:1687–1696
5.Park KW, et al. Vertebral Artery Dissection: Natural History, Clinical Features and Therapeutic Considerations. J Korean Neurosurg Soc.
6.Ruecker M, et al. Basilar artery dissection: series of 12 consecutive cases and review of the literature. Cerebrovasc Dis. 2010 Aug;30(3):267-76.
7.Yoshimoto Y, et al. Basilar artery dissection. J Neurosurg. 2005 Mar;102(3):476-81.
2019.3.20