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Fimbria of hippocampus

The fimbria of the hippocampus is a prominent white matter structure found along the medial aspect of the hippocampal formation within the temporal lobe. It serves as a major efferent pathway, carrying fibers from the hippocampus towards the fornix and ultimately to other limbic structures. The fimbria is easily identifiable on neuroimaging due to its position and signal characteristics and plays a crucial role in memory and cognitive processing.

Synonyms

  • Hippocampal fimbria

  • Fimbria hippocampi

Arterial Supply

  • Primarily supplied by branches of the posterior cerebral artery (PCA), specifically the hippocampal arteries.

  • Additional small branches from the anterior choroidal artery may also contribute.

Venous Drainage

  • Drained mainly via the hippocampal veins into the basal vein of Rosenthal.

  • Secondary drainage may occur via the inferior ventricular vein.

Function

  • Acts as a major output pathway for the hippocampus, transmitting efferent signals to the fornix.

  • Involved in memory consolidation and spatial navigation.

  • Facilitates communication between the hippocampus and other limbic system structures.

MRI Appearance

  • T1-weighted images: Appears as a thin, linear structure of low to intermediate signal intensity along the superomedial margin of the hippocampus.

  • T2-weighted images: Typically low signal intensity due to dense myelinated fibers.

  • FLAIR images: The fimbria remains hypointense, clearly demarcated from the adjacent hippocampal gray matter.

CT Appearance

  • Not distinctly visualized on standard CT due to its small size and low contrast from surrounding white matter.

  • May be indirectly identified by its anatomical position adjacent to the hippocampus, but is best seen on MRI.

MRI images

Fimbria of hippocampus mri 3t coronal image

MRI images

Fimbria of hippocampus mri 3t sagittal image