"Vertebral artery dissection occurs in younger people around 40 yrs(females more in vertebrals where as males more often affected in basilar dissections). Cervicocerebral artery dissection accounts for 2% of ischaemic strokes but in younger than 45 yrs it accounts for 10%, extracranial dissection is 80 to 90% cases , supraclinoid ICA and MCA stem have predilection for dissection.
An expanding hematoma in the vessel wall is the root lesion in arterial dissection in vertebral artery. Evolution: it can heal spontaneously or it can be subintimal and produce partial or complete block and also low flow state which can produce thrombus leading to shower of emboli as seen in this 45 yr old male with no history of trauma or it can be subadventitial which leads to pseudo-aneurysm formation
Crescent shaped thrombus and double lumen sign with intimal flap identification on MR are highly specific to dissection. Because of flow abnormalities, it is easier to appreciate intracranial dissections on T2 w images"
Reference- Z Han et al China. In Hongkong med journal Vol 13 No 2, Apr 2007
