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Aqueduct of midbrain (Sylvian Aqueduct)

The Aqueduct of Midbrain, also known as the Cerebral Aqueduct or Aqueduct of Sylvius, is a narrow channel located within the midbrain that connects the third ventricle to the fourth ventricle. This structure is crucial for the passage of cerebrospinal fluid (CSF) between these two ventricular spaces. Due to its small diameter, the aqueduct is a common site for obstruction, which can result in non-communicating hydrocephalus. The aqueduct runs through the dorsal aspect of the midbrain, surrounded by periaqueductal gray matter, and is visible on neuroimaging as a thin, CSF-filled structure.

Synonyms

  • Cerebral Aqueduct

  • Aqueduct of Sylvius

  • Sylvian Aqueduct

Arterial Supply

  • Primarily supplied by branches of the posterior cerebral artery (PCA), especially the quadrigeminal and thalamoperforating arteries.

  • Some minor contributions may come from branches of the superior cerebellar artery.

Venous Drainage

  • Drains mainly into the internal cerebral veins and the great cerebral vein (vein of Galen) through small periventricular veins.

  • Additional drainage into the basal veins of Rosenthal is also noted.

Function

  • Facilitates the flow of cerebrospinal fluid (CSF) from the third ventricle to the fourth ventricle.

  • Plays a vital role in maintaining CSF homeostasis and intracranial pressure.

  • Obstruction can lead to hydrocephalus, making its patency crucial for normal brain function.

MRI Appearance

  • T2-weighted Images:

    • Appears as a bright (hyperintense), thin, linear structure due to the high signal of CSF.

  • T1-weighted Images:

    • Appears dark (hypointense), mirroring the signal of CSF.

  • FLAIR:

    • Typically appears dark (signal-suppressed) as CSF is nulled on FLAIR sequences; the aqueduct may be less conspicuous compared to T2.

CT Appearance

  • Appears as a small, hypodense (dark) channel in the midbrain, best seen on thin-slice, high-resolution CT.

MRI images

Aqueduct of midbrain; Cerebral aqueduct (Sylvius) mri 3t axial image

MRI images

Aqueduct of midbrain; Cerebral aqueduct (Sylvius) mri 3t sagittal image