MRI and MR angiography of vertebral artery dissection

Abstract

A review of 4,500 angiograms yielded 11 patients with dissection of the vertebral arteries who had MRI and (in 4 patients) MR angiography (MRA) in the acute phase of stroke. One patient with incidental discovery at arteriography of asymptomatic vertebral artery dissection and two patients with acute strokes with MRI and MRA findings consistent with vertebral artery dissection were included. Dissection occurred after neck trauma or chiropractic manipulation in 4 patients and was spontaneous in 10. Dissection involved the extracranial vertebral artery in 9 patients, the extra-intracranial junction in 1, and the intracranial artery in 4. MRI demonstrated infarcts in the brain stem, cerebellum, thalamus or temporo-occipital regions in 7 patients with extra- or extra-intracranial dissections and a solitary lateral medullary infarct in 4 patients (3 with intracranial and 1 with extra-intracranial dissection). In 2 patients no brain abnormality related to vertebral artery dissection was found and in one MRI did not show subarachnoid haemorrhage revealed by CT. Intramural dissecting haematoma appeared as crescentic or rounded high signal on T1-weighted images in 10 patients examined 3-20 days after the onset of symptoms. The abnormal vessel stood out in the low signal cerebrospinal fluid in intracranial dissections, whereas it was more difficult to detect in extracranial dissections because of the intermediate-to-high signal of the normal perivascular structures and slow flow proximal and distal to the dissection. In two patients examined within 36 h of the onset, mural thickening was of intermediate signal intensity on T1-weighted images and high signal on spin-density and T2-weighted images. MRA showed abrupt stenosis in 2 patients and disappearance of flow signal at and distal to the dissection in 5. Follow-up arteriography, MRI or MRA showed findings consistent with occlusion of the dissected vessel in 6 of 8 patients.

Clinical and Neuroradiological Features of Intracranial Vertebrobasilar Artery Dissection

“…Although extracranial verte- bral artery dissection has been reported to be more common than intracranial vertebrobasilar artery dissection, 7,8,14,15,22 we found only 1 patient with extracranial vertebral artery dissection. Intracranial vertebrobasilar artery dissection is probably much more frequent than previously considered and is at least not a rare condition compared with extracranial vertebral artery dissection.…”

“…15 In the present study we described MR findings of 3 patients with subarachnoid hemorrhage. Intramural hematoma on T1-weighted images was clearly visible, except in 1 case with spread of a high-intensity clot within the cistern.…”

“…3,14,18,20,21 In addition, we observed progression of the angiographic findings in 2 patients, as previously observed. 7,14,15 In these patients, the initial angiograms performed within a week after onset revealed a localized stenosis or a mild arterial wall irregularity. The occurrence of spontaneous thrombosis or spontaneous thrombolysis of the pseudolumen may not be rare.…”

“…MR angiography is not able to demonstrate pathognomonic signs of arterial dissection, and MRI is more useful than MR angiography for the diagnosis. 15 In our department, MR angiography is not used for screening of the posterior circulation because we believe that contrast-enhanced 3-D SPGR is superior to MR angiography for this purpose; MR angiography does not demonstrate slow flow or thrombosed clot with low signal intensity within the pseudolumen. In addition, original images of MR angiography have a lower signal-to-noise ratio than those of contrast-enhanced 3-D SPGR.…”

“…14,15 However, the ultrasound technique does not have diagnostic value for intracranial arteries, and helical CT is also less reliable for detecting abnormality in the posterior fossa because of many artifacts. MR angiography is not able to demonstrate pathognomonic signs of arterial dissection, and MRI is more useful than MR angiography for the diagnosis.…”