Vertebrobasilar Supply to the Brain

1. Posterior Cerebral Artery (terminal branch of the vertebrobasilar system that supplies the inferior temporal lobe and the occipital lobe of the cerebral cortex)

1.1. Posterior Communicating Artery (IMPORTANT anastomosis between the carotid and vertebrobasilar system)

1.2. P1 Segment (posterior portion of the circle of Willis and the termination/bifurcation of the Basilar Artery to the junction of the posterior communicating artery (from ICA)

1.2.1. Posteriomedial Group (from P1 segment and Posterior Communicating Artery to supply the posterior hypothalamus, midbrain (including the crus cerebri and CST tract))

1.2.2. Thalamoperforating artery (supplies the anterior portion of the thalamus)

1.3. P2 Segment (posterior communicating to the branches that extend on the anterior pole of the temporal lobe of cerebral cortex)

1.3.1. Posteriolateral Group

1.3.1.1. Thalamogeniculate artery (supplies the posterior portion of the thalamus)

1.3.1.2. Posterior choroidal arteries (supplies the 3rd and lateral ventricles (choroid plexus))

1.4. P3 Segment (lateral branches over the inferior surface of the temporal and occipital lobes)

1.5. P4 Segment (medial branches that extend posteriorly to the occipital lobe)

1.5.1. Calcarine artery (supplies primary visual cortex)

2. Vertebral Artery

2.1. V1 Segment (from subclavian artery to the transverse process of C6)

2.2. V2 Segment (from C6 to C2)

2.3. V3 Segment (from C2 through the transverse foramen of the Atlas, to the atlantooccipital membrane)

2.4. V4 Segment (passes through the atlantooccipital membrane and the dura mater)

2.4.1. Anterior Spinal Artery (formed in the midline by anastomosing branches from left and right vertebral arteries to supply the ventral/midline medulla)

2.4.2. Posterior Inferior Cerebrellar Artery (aka PICA and is the MAIN branch off of V4 to supply the lateral medulla)

2.4.2.1. Posterior Spinal Artery (supplies the caudal-dorsal medulla (nucleus cuneatus, nucleus gracilis, spinal trigeminal nucleus)

2.4.2.2. Branch to supply the choroid plexus in the 4th ventricle

3. Basilar Artery (unpaired midline structure that is the LEFT-RIGHT Anastomosis of the Vertebral system)

3.1. Anterior Inferior Cerebellar Artery (supplies the caudolateral cerebellum as well as the inner ear (via the labyrinthine artery)

3.2. Paramedian branches (MOST median pontine branch)

3.3. Short circumferential branches (MOST middle pontine branch)

3.4. Long circumferential branches (MOST lateral pontine branches)

3.5. Superior cerebellar artery (LAST branch off the basilar artery that supplies the rostral (superior) cerebellum with small branches to the caudal midbrain)

3.6. Posterior Cerebral Artery (comes off the basilar artery as a bifurcation and the posterior extent of the circle of Willis)