The uncus (plural: unci) is the innermost part of the anterior parahippocampal gyrus, part of the mesial temporal lobe.

Gross anatomy

The uncus is the most anterior portion of the medial parahippocampal gyrus. It belongs to the limbic system. Housing the primary olfactory cortex, it is part of the olfactory system, receiving fibers from the olfactory tract via the lateral olfactory stria. It is divided into

  • anterior part
  • 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 and CA4, and covered by the alveus, the fimbria is attached to its extremity .

Arterial supply

The uncus is irrigated by uncal branches of the anterior choroidal artery most commonly, followed by branches of the middle cerebral artery (usually from the temporopolar artery), internal carotid artery, and posterior cerebral artery .

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 ), 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.

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