MRI AND MR-ANGIOGRAPHY OF VERTEBRAL ARTERY DISSECTION

A review of 4,500 angiograms yielded 11 patients with dissection of th e vertebral arteries who had MRI and (in 4 patients) MR angiography (M RA) in the acute phase of stroke. One patient with incidental discover y 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 spontan eous 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 ext ra-intracranial dis sections and a solitary lateral medullary infarct in 4 patients (3 with intracranial and 1 with extra-intracranial disse ction). In 2 patients no brain abnormality related to vertebral artery dissection was found and in one MRI did not show subarachnoid haemorr hage revealed by CT. Intramural dissecting haematoma appeared as cresc entic or rounded high signal on T1-weighted images in 10 patients exam ined 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 b ecause of the intermediate-to-high signal of the normal perivascular s tructures and slow flow proximal and distal to the dissection. In two patients examined within 36 h of the onset, mural thickening was of in termediate signal intensity on T1-weighted images and high signal on s pin-density and T2-weighted images. MRA showed abrupt stenosis in 2 pa tients and disappearance of flow signal at and distal to the dissectio n in 5. Follow-up arteriography, MRI or MRA showed findings consistent with occlusion of the dissected vessel in 6 of 8 patients.