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Rhinal sulcus

The rhinal sulcus, also known as the rhinal fissure, is a shallow groove located on the basal surface of the temporal lobe of the brain, close to the medial side. It plays a significant anatomical and functional role by demarcating the boundary between the parahippocampal gyrus and the uncus from the lateral aspect of the temporal lobe. It is considered a key landmark in neuroanatomy due to its close association with the entorhinal cortex, an area critical for memory and navigation.

Synonyms

  • Rhinal fissure

  • Fissura rhinalis

  • Sulcus rhinalis

Function

  • Anatomical landmark for the identification of the entorhinal cortex and parahippocampal gyrus.

  • Separates the lateral aspect of the temporal lobe from the limbic structures.

  • Plays a role in the organization of cortical regions involved in olfactory processing and memory integration.

Arterial Supply

  • Supplied primarily by branches of the posterior cerebral artery (PCA), particularly the anterior temporal branches.

  • Minor contributions may arise from branches of the middle cerebral artery (MCA), depending on vascular variation.

Venous Drainage

  • Venous blood is drained via small cortical veins that empty into the basal vein of Rosenthal.

  • Additional drainage can occur through the superficial middle cerebral vein and other adjacent temporal cortical veins.

MRI Appearance

  • T1-weighted imaging:

    • The rhinal sulcus appears as a hypointense (dark) linear groove separating gray matter structures.

    • The adjacent entorhinal cortex and parahippocampal gyrus are isointense to surrounding cortical gray matter.

  • T2-weighted imaging:

    • The sulcus is hyperintense (bright), filled with cerebrospinal fluid (CSF).

    • The surrounding cortex and subcortical white matter are seen with typical gray and white matter signal characteristics.

  • FLAIR (Fluid Attenuated Inversion Recovery):

    • The sulcus appears as a linear area of low signal intensity (dark) due to CSF suppression.

    • The cortical and subcortical anatomy remains well-delineated; no abnormal signal within the sulcus.

CT Appearance

  • The rhinal sulcus is generally not directly visualized on standard non-contrast CT due to its small size and the low contrast between brain structures.

  • May be inferred as a shallow groove on the basal temporal surface in high-resolution or thin-slice scans, especially with advanced post-processing.

MRI images

Rhinal sulcus MRI 3T axial image