Vascular diseases characterized by thickening, hardening, and remodeling of the walls of intracranial arteries. There are three subtypes: (1) atherosclerosis, marked by fatty depositions in the innermost layer of the arterial walls, (2) Monckeberg's sclerosis, which features calcium deposition in the media and (3) arteriolosclerosis, which refers to sclerosis of small caliber arteries. Clinically, this process may be associated with ISCHEMIC ATTACK, TRANSIENT; BRAIN INFARCTION; INTRACRANIAL EMBOLISM AND THROMBOSIS; or INTRACRANIAL ANEURYSM.