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Topic

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Parahippocampal gyrus

The parahippocampal gyrus is a prominent cortical fold in the medial temporal lobe of the brain, situated beneath the hippocampus. It plays a crucial role in memory encoding and retrieval, as well as spatial orientation. The parahippocampal gyrus forms part of the limbic system and is closely associated with the hippocampal formation and surrounding medial temporal structures. Its strategic position and connections make it essential for higher cognitive and emotional processing.

Synonyms

  • Parahippocampal region

  • Limbic gyrus (part of limbic lobe)

  • Gyrus parahippocampalis (Latin)

  • Hippocampal gyrus (historical/less common)

Arterial Supply

  • Primarily supplied by the anterior choroidal artery and posterior cerebral artery (PCA), especially its parahippocampal branches (PCA’s P2 segment).

  • Additional minor supply from branches of the anterior cerebral artery in some individuals.

Venous Drainage

  • Drains mainly into the basal vein of Rosenthal.

  • Additional drainage into the inferior ventricular vein and internal cerebral vein.

Function

  • Involved in memory encoding and retrieval, especially contextual and spatial memory.

  • Facilitates recognition of environmental scenes (scene recognition).

  • Plays a role in navigation and spatial orientation.

  • Involved in emotional processing and connections with the limbic system.

MRI Appearance

  • T2-weighted Imaging:

    • Parahippocampal gyrus appears as an isointense to mildly hyperintense cortical structure relative to other gray matter.

    • Pathology (e.g., gliosis, edema, sclerosis) may show increased signal intensity.

  • T1-weighted Imaging:

    • Appears as a gray matter structure, hypointense to white matter and hyperintense to cerebrospinal fluid (CSF).

    • Well-delineated cortical ribbon adjacent to the hippocampus.

  • FLAIR (Fluid Attenuated Inversion Recovery):

    • Normally isointense to adjacent cortex.

    • Pathological changes (e.g., mesial temporal sclerosis) may present as increased signal intensity or volume loss.

CT Appearance

  • Appears as a poorly differentiated cortical structure within the medial temporal lobe.

  • Gray matter density, similar to the surrounding cortex, but usually not distinctly visualized unless pathology (e.g., atrophy, mass lesion, calcification) is present.

  • Pathological changes may appear as hypo- or hyperdense areas, depending on the etiology.

MRI images

Parahippocampal gyrus MRI 3T axial image

MRI images

Parahippocampal gyrus MRI 3T sagittal image

CT image

Parahippocampal gyrus CT sag anatomy image -img-00001-00001