Precuneus

The precuneus is a part of the parietal lobe of the brain, lying on the medial surface of the cerebral hemisphere. It plays a role in visuo-spatial imagery, episodic memory retrieval and self-processing operations .

Gross anatomy

Relations

Posterior to the precuneus lies the cuneus, separated from from it by the medial portion of the parieto-occipital sulcus .

Anteriorly lies the paracentral lobule, separated from it by the pars marginalis (ascending branch of the cingulate sulcus) .

Inferiorly is located the cingulate gyrus, separated from it by the subparietal sulcus .

Blood supply

While highly variable, the main arterial supply arises from the posterior cerebral artery, predominantly the P2 segment. The precuneus derives blood supply from the occipito-parietal artery, a terminal branch of the internal occipital artery.

Practical points

The parieto-occipital sulcus joins with the anterior end of the calcarine sulcus to form a 'lazy Y' configuration, sometimes referred to as the parieto-occipito-calcarine sign . The precuneus lies superior to the upper limb of the Y (parieto-occipital sulcus), whereas the cuneus lies in between the two limbs, and the lingual gyrus below the lower limb.