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Collateral sulcus

The collateral sulcus (also called the collateral fissure) is a prominent longitudinal groove located on the basal (inferior) surface of the temporal and occipital lobes of the brain. It plays a crucial anatomical role by demarcating the boundary between the parahippocampal gyrus medially and the fusiform gyrus laterally. The collateral sulcus is particularly important as a neuroimaging landmark and in the context of temporal lobe and medial occipital lobe anatomy.

Synonyms

  • Collateral fissure

  • Sulcus collateralis (Latin)

Function

  • Serves as an anatomical landmark separating the parahippocampal and fusiform gyri

  • Helps in the identification and orientation of medial temporal lobe structures on imaging

  • Indirectly supports memory and visual processing by demarcating associated gyri

Arterial Supply

  • Supplied mainly by branches of the posterior cerebral artery (PCA), specifically:

    • Parahippocampal artery (branch of PCA)

    • Posterior temporal branches (branch of PCA)

Venous Drainage

  • Drains primarily into the basal vein of Rosenthal

  • May also contribute to the inferior ventricular veins and ultimately drain into the great cerebral vein (vein of Galen)

MRI Appearance

  • T2-weighted MRI:

    • The collateral sulcus appears as a deep, well-defined hyperintense (bright) groove because CSF within the sulcus is bright on T2-weighted images. It separates the parahippocampal and fusiform gyri.

  • T1-weighted MRI:

    • The sulcus is seen as a hypointense (dark) line filled with CSF between the medial and lateral gyri, as CSF appears dark on T1-weighted images.

  • FLAIR MRI:

    • The sulcus contains CSF, which appears hypointense (dark) since FLAIR suppresses the signal from free fluid; the sulcus stands out as a dark line between gyri.

CT Appearance

  • On non-contrast CT, the collateral sulcus appears as a linear hypodense (dark) area due to the presence of CSF, clearly separating the parahippocampal and fusiform gyri. It is better visualized in cases of cortical atrophy or brain volume loss.

MRI images

Collateral sulcus mri 3t axial image

MRI images

Collateral sulcus mri 3t sagittal image