Intracranial vessels lack vasa vasorum.

A micro-corrosion technique was used to demonstrate an extensive vasa vasorum network in extracranial vessels but did not reveal this system in intracranial vessels of comparable size in three species of animals. The absence of a vasa vasorum network in cerebral vessels may result in a higher level of susceptibility to periarterial abnormalities, such as cerebral vasospasm secondary to subarachnoid hemorrhage.