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Crus of fornix

The crus of fornix is a key white matter tract within the limbic system, connecting the hippocampus to various subcortical structures. It forms part of the larger fornix structure, beginning as a continuation of the fimbria of the hippocampus and arching superiorly and medially beneath the corpus callosum. The crus of fornix is crucial for memory processing, serving as a main output pathway from the hippocampus to the mammillary bodies and septal nuclei.

Key Points:

• Location and Structure:

  • The crus of fornix arises bilaterally from the posterior part of the hippocampal formation (fimbria).

  • It curves upwards and forwards beneath the splenium of the corpus callosum.

  • Joins its counterpart at the midline to form the body of the fornix.

  • Lies superior to the thalamus and inferolateral to the lateral ventricles.

• Function:

  • Serves as a major efferent pathway from the hippocampus.

  • Facilitates transmission of information to the mammillary bodies and septal nuclei.

  • Integral for memory formation and spatial navigation.

• MRI Appearance:

  • T1-weighted MRI: Crus of fornix appears as a linear structure intermediate to slightly hyperintense signal intensity, due to its myelinated white matter composition.

  • T2-weighted MRI: Shows as a low signal intensity tract, contrasting against the high-signal cerebrospinal fluid (CSF) of adjacent ventricles.

  • FLAIR: Remains hypointense, maintaining good contrast with the hyperintense CSF, allowing clear delineation from surrounding structures.

• CT Appearance:

  • The crus of fornix is not well visualized on CT due to its fine structure and similarity in density to adjacent white matter.

  • May appear as a subtle linear density if the image quality is high, but typically indistinct from the corpus callosum and other white matter tracts.

MRI images

Crus of fornix mri 3t sagittal image

MRI images

Crus of fornix mri 3t coronal image