Vascular anatomy

 

Cerebral hemispheres의 vascular territories

Circle of Willis viewed from in front of and below the brain

Circle of Willis

A balanced configuration of the Circle of Willis is present in only 18% of the population. Hypoplasia of 1 or both p-comms occurs in 22–32%, absent or hypoplastic A1 segments occurs in 25%.

Key point: the anterior cerebral arteries pass over the superior surface of the optic chiasm

 

ICA segment

VA segment

•  V1 prevertebral: from subclavian artery, courses superiorly and posteriorly and enters the foramen transversarium, usually of the 6th vertebral body
• V2 ascends vertically within the transverse foramina of the cervical vertebrae surrounded by sympathetic fibers (from the stellate ganglion) and a venous plexus. It is situated anterior to the cervical roots. It turns laterally to enter the foramen within the transverse process of the axis
• V3 exits the foramen of the axis and curves posteriorly and medially in a groove on the upper surface of the atlas and enters the foramen m agnum
• V4 pierces the dura (location som ew hat variable) and immediately enters the subarachnoid space. Joins the contralateral VA at the vertebral confluens located at the lower pontine border to form the basilar artery (BA)

 

ACA segment

• A1 ; horizontal or precommunicating segment
  • Medial lenticulostriate arteries
• A2 ; vertical or postcommunicateing segment
  • Recurrent artery of Heubner(=medial striatal a.)
  • Corpus callosum genu, septum pallucidum, column of fornix
• A3 ; distal ACA and cortical branches
  • Pericallosal artery
  • Callosomarginal artery
  • Cortical br.

ACA (lateral view)

MCA (lateral view)

Intradural VA and PICA segments (lateral view)

 

BA segment

Basilar artery: Formed by the junction of the 2 vertebral arteries.

 

Vetebrobasilar arteriogram ( lateral view)

Carotid-vertebrobasilar anastomoses

 

Anatomic segments of the PCA and their branches