Figure 8 (A) Extracranial vertebral artery transverse section from a 17 year old subject, showing mild to moderate elastic fibre fragmentation (E₁–E₂). (B) Extracranial vertebral artery section from a 33 year old subject. Note the advanced elastic fibre fragmentation (E₃) and severe collagen scarring (C₃). (C) Transverse vertebral artery section from the upper cervical loop segment of a 30 year old subject. Note the very dense distribution of collagen extending from the adventitia into the media. (D) Transverse vertebral artery section from the upper cervical loop segment of a 33 year old subject. Again, note the unusual arrangement of peripheral collagen extending from the adventitia (all stained with picro-sirius red).