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Interventricular foramen

The interventricular foramen, also known as the foramen of Monro, is a crucial anatomical channel in the brain that connects each lateral ventricle to the third ventricle, allowing cerebrospinal fluid (CSF) to flow between them. It plays a vital role in the ventricular system and CSF circulation. Obstruction or abnormalities at the foramen of Monro can lead to significant neurological symptoms, such as obstructive hydrocephalus. On neuroimaging, this foramen is not directly visualized unless pathologically enlarged or distorted, but its location and patency are assessed indirectly through ventricle morphology and surrounding structures.

Synonyms

  • Foramen of Monro

  • Monro’s foramen

  • Interventricular foramen of Monro

MRI Appearance

  • T1-weighted Imaging

    • The foramen of Monro itself is not directly visible as it is a small CSF-filled channel.

  • T2-weighted Imaging

    • CSF in the foramen of Monro is hyperintense (bright), matching the appearance of ventricular CSF.

  • FLAIR Imaging

    • CSF signal in the foramen of Monro is suppressed (dark), similar to other CSF spaces.

CT Appearance

  • The foramen of Monro is not directly visualized on CT due to its small size.

  • Its anatomical location is inferred as the connection between the frontal horns of the lateral ventricles and the third ventricle.

  • Dilation of the lateral ventricle(s) with normal or small third ventricle may indicate obstruction at the foramen of Monro.

MRI images

Interventricular foramen (Monro) mri 3t coronal image