Age-related changes in reticulin fibers and other connective tissue elements in the intima of the major intracranial arteries.

The results of post mortem histological studies on the major intracranial arteries from 150 individuals, whose age varied from one day to 80 years are reported. Patients with specific vascular diseases or severe atherosclerosis were excluded. The work resulted in the following conclusions: 1) The existence of 3 types of so-called pseudoelastic fibers can be revealed by light microscopic staining procedures. All of them share some staining characteristics of true elastic fibers. Types 1 and 2 also stain to a certain extent like reticulin fibers. Type 3 pseudoelastic fibers resemble collagen fibers in some of their staining qualities. 2) At birth the internal elastic lamina (IEL) consists of true elastic fibers and type 1 pseudoelastic fibers. 3) These 2 fibers are present throughout life, though from the age of two years, type 2 pseudoelastic fibers become additional but permanent components of IEL. 4) Aging is accompanied by the appearance of collagen fibers. The relative proportion of different fibers within the IEL seems to follow a consistent sequence of changes. 5) The appearance of type 3 pseudoelastic and/or collagen fibers indicates abnormality since it is inevitably associated with loss of elasticity of the vessel wall.