Arterial dissections result from a split in the vascular wall caused by a hematoma. There are two types of dissection, subintimal (on the inner surface of the wall) and subadventitial (on the outer surface of the wall). The hematoma on the wall may be the result of a break in the lumen of the vessel or a hemorrhage within the wall supplied by microscopic vessels (vasa-vasorum).
The dissections responsible for ICHs occur in an cephalic artery, usually a carotid artery or a vertebral artery in the neck, more rarely an intracranial artery. In most groups of patients, the dissections occur in several arteries in 10 to 20% of cases.
Spontaneous dissections (with no trauma) of the carotid or vertebral arteries are usually sporadic. They are rarely detected in several members of the same family.
Familial types of dissections are rare. They are defined as the occurrence of a spontaneous arterial dissection in at least two members of the same family.