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Interthalamic adhesion

The interthalamic adhesion (also known as the massa intermedia) is a midline, oval or circular band of gray matter connecting the medial surfaces of the thalami across the third ventricle. Not present in all individuals, its size and presence can vary significantly. This non-neuronal structure does not contain major neural tracts but is a common anatomical variant seen on brain imaging.

Synonyms

  • Massa intermedia

  • Middle commissure of thalamus

  • Interthalamic mass

Function

  • No major neural function: The interthalamic adhesion does not contain significant neural pathways and is not essential for thalamic communication.

  • Anatomical landmark: It serves primarily as an anatomical landmark in neuroimaging and neuroanatomy.

  • Possible minor role: Some studies suggest a minor role in thalamic adhesion or cerebrospinal fluid (CSF) dynamics, but clinical significance is minimal.

MRI Appearance

  • T1-weighted MRI:

    • Appears as a small, round to oval isointense structure within the third ventricle, connecting the thalami.

    • Signal intensity is similar to surrounding gray matter.

  • T2-weighted MRI:

    • Isointense or slightly hyperintense compared to thalamic gray matter.

    • Seen as a thin or small midline band bridging the thalami within the third ventricle.

  • FLAIR MRI:

    • Isointense to thalamic gray matter.

    • Best visualized when third ventricle fluid provides contrast; appears as a thin, midline structure.

CT Appearance

  • Non-contrast CT:

    • Difficult to visualize due to similar density to brain parenchyma.

    • May appear as a faint, thin midline soft-tissue band connecting the medial thalami, best appreciated in thin-slice imaging.

MRI images

Interthalamic adhesion mri 3t axial image