Topics

Topic

design image
Median aperture of the fourth ventricle

The median aperture of the fourth ventricle, also known as the foramen of Magendie, is a crucial anatomical opening in the brain’s ventricular system. It serves as a communication channel, allowing cerebrospinal fluid (CSF) to flow from the fourth ventricle into the cisterna magna, an important subarachnoid cistern at the base of the brain. Proper function of the median aperture is essential for normal CSF circulation, and its obstruction can contribute to conditions such as non-communicating hydrocephalus.

Anatomical Description

  • The median aperture is located in the caudal (inferior) portion of the roof of the fourth ventricle.

  • It is positioned in the midline, between the cerebellum and the medulla oblongata.

  • The aperture opens posteriorly into the cisterna magna.

  • It is one of three openings in the fourth ventricle, the other two being the paired lateral apertures (foramina of Luschka).

Synonyms

  • Median aperture of the fourth ventricle

  • Foramen of Magendie

  • Apertura mediana ventriculi quarti (Latin)

MRI Appearance

T2-Weighted MRI:

  • CSF within the fourth ventricle and cisterna magna appears hyperintense (bright) on T2.

  • The median aperture itself is not directly visualized but is inferred by the continuity of bright CSF signal between the ventricle and cisterna magna.

  • No distinct wall or anatomical margin is seen, but a smooth, uninterrupted flow of hyperintense signal confirms patency.

T1-Weighted MRI:

  • CSF appears hypointense (dark) on T1 images.

  • The median aperture is again not directly visible; its location is inferred by the dark CSF signal connecting the fourth ventricle to the cisterna magna.

  • Any interruption in this continuity may suggest obstruction.

FLAIR MRI:

  • CSF is suppressed and appears very dark on FLAIR images.

  • The median aperture is seen as a gap where dark CSF extends from the fourth ventricle into the cisterna magna.

  • Pathology such as obstruction may be better appreciated if there is abnormal signal intensity in these regions.

CT Appearance

  • On non-contrast CT, CSF appears hypodense (dark/black).

  • The median aperture itself is not distinctly visualized but is inferred by the continuity of low attenuation (black) CSF between the fourth ventricle and the cisterna magna.

  • Obstruction may present as enlargement of the fourth ventricle with absence of normal cisterna magna filling.

MRI images

Median aperture of fourth ventricle mri 3t axial image

MRI images

Median aperture of fourth ventricle mri 3t sagittal image