Occipital pole

At a glance

English

Occipital pole

Latin (TA2)

Polus occipitalis

System

Brain and spinal cord

Region

Head

Side

Paired, left and right

About the occipital pole

The occipital pole is the most posterior point of each cerebral hemisphere. It is one of three poles used to orient the hemisphere, the others being the frontal pole at the front and the temporal pole at the forward tip of the temporal lobe. The occipital pole forms the back end of the occipital lobe and lies just above the tentorium cerebelli, the fold of dura mater that separates the cerebrum from the cerebellum, close to the inner surface of the occipital bone.

The pole is where the lateral, medial and inferior (tentorial) surfaces of the hemisphere meet. On the medial surface, the deep calcarine sulcus runs forwards from near the pole, and the cortex on its banks is the primary visual cortex. In many brains the calcarine sulcus reaches, or even curves round, the pole onto the lateral surface, where it may be bounded by small lunate and transverse occipital sulci. The cuneus lies above the calcarine sulcus and the lingual gyrus below it.

Functionally, the region around the occipital pole is part of the visual cortex. Visual space is mapped across the striate cortex in an orderly way, and the central part of the visual field, the area seen by the macula, is represented in a relatively large territory at and near the pole. Peripheral parts of the visual field are mapped further forwards along the calcarine sulcus. Surrounding association areas on the lateral surface help to interpret shape, colour and movement.

Its blood supply is shared. Branches of the posterior cerebral artery, especially the calcarine and medial occipital branches, supply most of the occipital lobe, but the tip of the pole is often also reached by terminal branches of the middle cerebral artery. This dual supply explains macular sparing: after a stroke in the posterior cerebral territory, a person may lose half of the visual field yet keep central vision. A blow to the back of the head can bruise the pole against the skull and disturb vision.

Function and supply

Function

Contains part of the primary visual cortex and its surrounding association areas; the representation of central (macular) vision lies at and near the pole.

Blood supply

Branches of the posterior cerebral artery, mainly the calcarine and medial occipital arteries, with a contribution from terminal branches of the middle cerebral artery at the tip of the pole.