Circular sulcus

Last revised by Craig Hacking on 12 Feb 2023

The circular sulcus, or peri-insular sulcus is a deep sulcus that surrounds the lateral surface of the insular cortex and separates it from the operculum of the frontal, temporal and parietal lobes. In this sulcus, the M2 segment of the middle cerebral artery (MCA) completes a downward turn at the superior and inferior limiting sulci of the insula and passes into the opercular compartment to become the M3 segment of the MCA.

Gross anatomy

The circular sulcus can more precisely be divided into four peri-insular sulci: anterior, inferior, superior, and posterior. The circular sulcus is contiguous with the lateral (Sylvian) sulcus forming part of the operculoinsular compartment of the Sylvian fissure3.

History and etymology

The circular sulcus is also known as the circular sulcus of Reil, named after German anatomist, physiologist and pioneer psychiatrist Johann Christian Reil (1759-1813) 7.

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Cases and figures

  • Fig 1: Insula and operculum (annotated MRI)
    Drag here to reorder.