Uncus

The uncus is the innermost part of the temporal lobe. 

Gross anatomy

The uncus lies medial to the parahippocampal gyrus. It belongs to the limbic system. Housing the primary olfactory cortex, it is part of the olfactory system, receiving fibres from the olfactory tract via the lateral olfactory stria.It is divided into anterior, and posterior parts. The posterior part belongs to the hippocampus. The anterior part is identified by two protrusions; ambient, and semilunar gyri. The semilunar gyrus is best identified by the semilunar sulcus .The inferior surface of the uncus is crossed by a transverse marking; the band of Giacomini, which represents the rostral end of the dentate gyrus. Posterior to the band of Giacomini, the uncal apex is formed of CA3 & CA4, and covered by the alveus, the fimbria is attached to its extremity ⁴.

Blood supply

Primary it is served by uncal arteries, small branches arising from the M1 segment of the middle cerebral artery (MCA). However, it can also be partially supplied by small branches from the posterior cerebral artery (PCA). 

Related pathology

The uncus is a common origin of temporal lobe seizures. Seizures starting in the uncus may be preceded by olfactory or gustatory hallucinations (uncinate fits ³), hence the antiquated term rhinencephalon for its developmental origin.

The uncus is also featured in the term uncal herniation (downward transtentorial herniation of the uncus).

History and etymology

Uncus is Latin for "hook", referencing its shape.