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Topic

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Cornu ammonis 2 (CA2)

Cornu Ammonis 2 (CA2) is a distinct and small subfield of the hippocampus located between the CA1 and CA3 regions. Although smaller than its neighboring subfields, CA2 has unique cellular organization and functions, contributing to memory processing and social behavior. It is known for its resistance to some forms of neuronal injury and distinct immunohistochemical properties.

Synonyms

  • Hippocampal area CA2

  • CA2 field

  • Hippocampal sector 2

Arterial Supply

  • Supplied primarily by branches of the posterior cerebral artery (PCA)

  • The anterior choroidal artery also provides some perfusion

  • Minor contributions may arise from hippocampal arteries, especially the middle and inferior hippocampal arteries

Venous Drainage

  • Drains into the hippocampal veins

  • Venous blood is eventually collected by the basal vein of Rosenthal

  • Secondary drainage into the internal cerebral vein

Function

  • Involved in social memory (recognition of conspecifics)

  • Plays a role in episodic memory processing

  • Acts as a relay station for signals between CA3 and CA1

  • Less prone to hypoxic-ischemic injury compared to CA1

  • Unique in expressing specific molecular markers such as PCP4

MRI Appearance

  • T2-weighted:

    • Appears as part of the hippocampal formation with intermediate signal intensity

    • Difficult to delineate from neighboring CA regions unless there is pathology

  • T1-weighted:

    • Isointense to the surrounding gray matter of the hippocampus

    • Not individually distinguishable under normal circumstances

  • FLAIR:

    • Follows the general signal pattern of the hippocampus

    • May show increased signal in cases of hippocampal sclerosis, but CA2 is often relatively spared compared to CA1

CT Appearance

  • Not clearly distinguishable from other hippocampal subfields on routine CT

  • Appears as part of the general hippocampal structure

  • Atrophy or loss of volume may be indirectly inferred in chronic epileptic conditions, but differentiation from other sectors is limited

MRI images

Cornu Ammonis 2 (CA 2) coronal mri 3t image