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Posterior ramus of lateral sulcus

The posterior ramus of the lateral sulcus (also known as the posterior horizontal ramus of the Sylvian fissure) is a prominent anatomical feature on the lateral surface of the human cerebral hemisphere. It forms the main posterior extension of the lateral sulcus, separating portions of the frontal, parietal, and temporal lobes. This sulcal structure is clinically significant as it serves as an important landmark in neuroimaging and neurosurgery for localization of cortical areas and deep structures. Its precise anatomy, vascular supply, and imaging appearance are crucial for radiological interpretation and surgical planning.

Synonyms

  • Posterior horizontal ramus of the lateral sulcus

  • Posterior ramus of Sylvian fissure

  • Pars posterior sulci lateralis

  • Sulcus lateralis posterior ramus

Function

  • Serves as an anatomical landmark demarcating the boundary between the parietal and temporal lobes.

  • Provides orientation for locating the supramarginal gyrus and surrounding cortical regions.

  • Assists in delineating the opercular areas during surgical approaches.

  • No direct functional role, but indirectly related to regions involved in language and auditory processing.

Arterial Supply

  • Supplied primarily by branches of the middle cerebral artery (MCA), especially the cortical branches traversing the Sylvian fissure.

  • Small perforating arteries may arise from the MCA to supply adjacent opercular cortex.

Venous Drainage

  • Drained by superficial middle cerebral veins running parallel to the lateral sulcus.

  • Venous blood ultimately empties into the cavernous sinus or sphenoparietal sinus.

MRI Appearance

  • T1-weighted images:

    • Appears as a hypointense (dark) linear structure between the isointense cortical gyri, filled with CSF (cerebrospinal fluid).

    • Clearly separates adjacent cortical areas.

  • T2-weighted images:

    • CSF within the sulcus appears hyperintense (bright), making the sulcus more conspicuous.

    • Well delineated from the adjacent brain parenchyma.

  • FLAIR images:

    • CSF signal in the sulcus is suppressed (appears dark), highlighting the sulcal space as a dark line among the brain tissue.

    • Useful in detecting subtle abnormalities in adjacent cortex.

CT Appearance

  • The posterior ramus of the lateral sulcus appears as a hypodense (dark) linear structure due to the presence of CSF.

  • Functions as an anatomical separator between the high-density brain parenchyma of the parietal and temporal lobes.

  • May become more prominent in cases of atrophy, edema, or mass effect.

MRI images

Posterior ramus of lateral sulcus MRI 3T sagittal image