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Inferior colliculus

The inferior colliculus is a paired, rounded structure located in the dorsal midbrain, playing a crucial role in the central auditory pathway. It acts as a major relay and processing center for auditory information traveling from the cochlear nuclei to the medial geniculate body of the thalamus. Due to its central position and functional importance, understanding its anatomical features, blood supply, venous drainage, and imaging characteristics is essential for accurate diagnosis and management of related neurological conditions.

Synonyms

  • Colliculus inferior

  • Inferior quadrigeminal body

Arterial Supply

  • Primary arterial supply: Quadrigeminal artery (branch of the posterior cerebral artery, PCA)

  • Additional contributions from:

    • Superior cerebellar artery

    • Posterior choroidal arteries (branches of PCA)

Venous Drainage

  • Drained primarily via the quadrigeminal vein (also called the vein of Galen)

  • Additional drainage through:

    • Superior petrosal veins

    • Basal vein of Rosenthal

Function

  • Auditory processing: Acts as a major relay center for auditory information.

  • Integration of auditory reflexes: Mediates startle and orientation reflexes to sound.

  • Multisensory integration: Processes some visual and somatosensory signals related to localization of sound.

  • Relay to thalamus: Projects to the medial geniculate body, which then relays auditory signals to the auditory cortex.

MRI Appearance

  • T2-weighted images:

    • Inferior colliculi appear as paired, oval to round structures at the dorsal midbrain, showing intermediate to low signal intensity relative to the surrounding tegmentum.

  • T1-weighted images:

    • Usually isointense to gray matter; clearly delineated due to adjacent CSF in the quadrigeminal cistern.

  • FLAIR images:

    • Similar appearance to T2; however, background suppression of CSF may make the colliculi more conspicuous against the quadrigeminal cistern.

CT Appearance

  • Non-contrast CT:

    • Inferior colliculi are not distinctly visualized; they blend with the surrounding midbrain parenchyma, appearing isodense to other gray matter structures.

  • CT with contrast:

    • May slightly enhance, but still not individually distinguishable unless there is pathology (e.g., hemorrhage, calcification, or mass).

MRI images

Inferior colliculus mri 3t axial image

MRI images

Inferior colliculus mri 3t sagittal image