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Brachium of inferior colliculus

The brachium of the inferior colliculus is a prominent bundle of white matter fibers in the midbrain that connects the inferior colliculus to the medial geniculate body of the thalamus. As an integral component of the auditory pathway, it plays a crucial role in relaying auditory information from the midbrain to the thalamus, and subsequently to the auditory cortex. Its precise anatomical position and distinct imaging characteristics are important for radiological identification and for understanding brainstem function in both health and disease.

Synonyms

  • Inferior collicular brachium

  • Brachium colliculi inferioris (Latin)

  • Auditory brachium (in certain contexts)

Arterial Supply

  • Supplied primarily by the quadrigeminal artery (branch of the posterior cerebral artery)

  • Contributions may come from the superior cerebellar artery

  • Occasionally, small perforating branches from the posterior cerebral artery (PCA) may also supply the area

Venous Drainage

  • Drains mainly into the internal cerebral veins

  • Additional drainage into the great cerebral vein of Galen

  • Minor drainage to the superior petrosal sinus

Function

  • Serves as a conduit for auditory signals from the inferior colliculus to the medial geniculate body (MGB) of the thalamus

  • Essential for auditory processing and sound localization

  • Involved in the reflexive response to auditory stimuli

MRI Appearance

  • T1-weighted images: Appears as a linear structure with intermediate (isointense to slightly hypointense) signal compared to surrounding brainstem tissue

  • T2-weighted images: Demonstrates a slightly hyperintense to isointense signal, helping to distinguish the white matter tract from adjacent grey matter

  • FLAIR: The brachium itself typically does not enhance on FLAIR unless there is pathology (such as demyelination or inflammation), in which case hyperintensity may be seen

CT Appearance

  • Not well visualized as a discrete structure on non-contrast CT due to limited resolution for white matter tracts

MRI images

Brachium of inferior colliculus mri axial image