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Topic

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Hippocampal sulcus

The hippocampal sulcus, also known as the hippocampal fissure, is a shallow, narrow cleft located in the medial temporal lobe of the brain. It is positioned between the dentate gyrus and the subiculum of the hippocampal formation. This sulcus plays a significant role during brain development as it marks the site of infolding that leads to the formation of the hippocampus and surrounding structures. In adults, the hippocampal sulcus is typically seen as a small, CSF-filled space, best appreciated on high-resolution neuroimaging. Recognition of this sulcus is important in both anatomical studies and clinical imaging, especially when evaluating hippocampal pathology.

Synonyms

  • Hippocampal fissure

  • Fissura hippocampi (Latin)

Function

  • Acts as an embryological landmark for hippocampal development.

  • Separates the dentate gyrus from the subiculum and cornu ammonis (CA).

  • Has no direct functional role in adults but is crucial as an anatomical boundary within the hippocampal formation.

Arterial Supply

  • Supplied primarily by branches of the posterior cerebral artery (PCA), especially the hippocampal branches.

  • Minor contributions may come from anterior choroidal artery branches.

Venous Drainage

  • Drained by the hippocampal veins.

  • Venous blood from this region ultimately drains into the basal vein of Rosenthal.

MRI Appearance

  • T2-weighted imaging: The hippocampal sulcus appears as a hyperintense (bright) linear or curvilinear structure due to the presence of cerebrospinal fluid (CSF).

  • T1-weighted imaging: The sulcus is hypointense (dark), again reflecting the CSF signal.

  • FLAIR imaging: The sulcus is typically suppressed (dark), as FLAIR nulls the CSF signal, making the sulcus less conspicuous but still discernible as a thin cleft.

CT Appearance

  • The hippocampal sulcus is usually not visualized on routine CT scans due to its small size and lack of contrast between CSF and adjacent gray matter.

MRI images

Hippocampal sulcus MRI 3T axial image