Imaging diagnosis is
Case 302
【Progress】
She was transported to neuro-surgeon hospital where she underwent surgical blood vessel reconstruction with trapping aneurysm associated with anastomosis between right external carotid artery and left vertebral artery using native graft of right radicular artery was performed.
Post-surgery angiography revealed good run-off of the artificial circuit.
【Discussion】
Vertebral artery is segmented into four parts; V1, from subclavian artery to transverse process foramen C5/C6; V2, transverse process foramen from C5/C6 to C2; V3, from transverse process foramen of C2 to entry into the skull (foramen magnum): V4, from foramen magnum embedded in dura mater to distal end of basilar artery in arachnoid space. Vertebral artery dissection usually occurs at V2 or V3 extended to V4.
Of the cranial arteries, vertebral artery dissection occurs one of the most, followed by carotid artery dissection with almost equal incidence (1-8). In western countries, carotid artery dissection is reported to be more than vertebral artery dissection, while in Japan, vice versa (1-4). They occur at ages of 50ies or 60ies. They are caused by trauma, chiropractic athletics, hypertension and spontaneous (1-8).
Symptoms of vertebral artery dissection are sudden neck and hemi lateral occipital pain caused by dissection itself. Further, it causes dizziness, difficulty speaking, impaired coordination secondarily to dissection.
Artery wall composes of four layers: tunica intima, internal elastic lamina, tunica media and tunica adventitia. Artery dissection implies disruption of internal tunica and internal elastic lamina, inducing blood flow enter slit space to sparce area of medial tunica, forming hematoma in vascular wall or subarachnoid hemorrhage to extra-vessel-wall space by vascular wall rupture. Vascular wall hematoma and disruption of intima tunica induce irregularity of vessel wall, narrowing vascular lumen and/or thrombus formation leading ischemia and/or distant embolism (5-8).
It is important to find out vertebral artery dissection in imaging modality. MRI contributes to it using several sequences. First, by comparison of images of BPAS and MRA, the configuration of vertebral artery can be grasped. MRA is formed in maximum intensity projection of TOF that collect signals of blood flow out separating from cardiac outputs, implying vascular lumen images. BPAS is a flip images of CSF, implying the outer images of vessels. Then, it is possible to differentiate hypoplasia of vertebral artery from occlusive vertebral artery by comparison BPASS with MRA. Vascular wall hematoma can be identified to be high signal intensity on T1WI, fat suppression T1WI, FLAIR and Diffusion WI, and to be low signal intensity on T2WI and low values on ADC mapping (9).
In our case, vertebral artery dissection was scanned with sequences of T1WI, T2WI and MRA in 2012. Then, MRI sequences of FLAIR, fat suppression T1WI and Diffusion WI were not conducted. Pseudoaneurysm of vertebral artery was demonstrated high signal intensity on T1WI and low signal intensity on T2WI. Finally, CT angiography depicted pseudoaneurysm of vertebral artery due to dissection.
【Summary】
We presented a fifty nine-year-old female with vomit and nausea. Pseudoaneurysm of vertebral artery was demonstrated high signal intensity on T1WI and low signal intensity on T2WI. Finally, CT angiography depicted pseudoaneurysm due to right vertebral artery dissection. It is borne in mind that for approach to an exact diagnosis of vertebral artery dissection, the first step is to check the presence or absence of vertebral artery lumen on MRA, the next step is to check the outer configuration of vertebral artery on BPAS in case of lumen stenosis or occlusion, the third step is to investigate mural hematoma that appears high signal intensity on TIWI, fat-suppression T1WI, FLAIR, DWI and low signal intensity on T2WI and low values on ADC.
【References】
1.Goodfriend SD, et al. Carotid Artery Dissection. National Center for Biotechnology Information, U.S. National Library of Medicine.. Retrieved 11 February 2023.
2.Mokri B. Spontaneous dissections of internal carotid arteries". Neurologist. 1997 3 (2): 104–119.
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8.Yun SY, et al. Spontaneous intracranial vertebral artery dissection with acute ischemic stroke: High-resolution magnetic resonance imaging findings. Neuroradiol J. 2018 Jun;31(3):262-269.
9.McNally JS, et al. Magnetic Resonance Imaging and Clinical Factors Associated With Ischemic Stroke in Patients Suspected of Cervical Artery Dissection. Stroke. 2018 Oct;49(10):2337-2344.
2023.6.23