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Topic

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Lateral aperture of fourth ventricle (foramen of Luschka)

The lateral apertures, also known as foramina of Luschka, are paired openings in the lateral recesses of the fourth ventricle, which communicate the ventricular system with the subarachnoid space. Each foramen is located at the junction of the lateral recess and cerebellopontine angle, adjacent to the flocculus of the cerebellum and near the cranial nerves VII (facial) and VIII (vestibulocochlear).

These apertures are critical for cerebrospinal fluid (CSF) circulation, allowing CSF to exit the fourth ventricle and enter the pontine cistern and cerebellopontine angle cistern, ultimately reaching the subarachnoid space of the brain and spinal cord. Malformations or obstruction of the foramina of Luschka can lead to hydrocephalus.

Function

  • Serves as an outflow channel for CSF from the fourth ventricle to the subarachnoid space

  • Maintains normal CSF circulation and intracranial pressure

  • Plays a role in ventricular system dynamics

  • Clinical importance in hydrocephalus, congenital malformations, or tumors near the cerebellopontine angle

Synonyms

  • Foramen of Luschka

  • Lateral foramen of the fourth ventricle

  • Lateral apertures of fourth ventricle

MRI Appearance

T1-weighted images:

  • The lateral apertures themselves are tiny CSF-filled channels, appearing hypointense (dark) relative to brain tissue

  • Surrounding cerebellopontine angle structures, cranial nerves, and flocculus are isointense

  • CSF obstruction or mass lesions at the foramen may cause ventricular enlargement upstream

T2-weighted images:

  • CSF within the lateral apertures is hyperintense (bright), providing high contrast against surrounding brain tissue

  • Small size makes them often difficult to directly visualize, but associated ventricular dilatation or cisternal effacement can indicate blockage

  • Adjacent cranial nerves and brainstem structures are intermediate signal

STIR (Short Tau Inversion Recovery):

  • CSF remains hyperintense, with fat suppression helpful for identifying abnormal soft tissue masses, inflammation, or cysts near the aperture

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal foramina do not enhance

  • Pathological enhancement may indicate tumors, vascular malformations, or inflammatory processes near the cerebellopontine angle or fourth ventricle

CT Appearance:

  • On non-contrast CT, the lateral apertures are not directly visible due to small size

MRI images

Lateral aperture of fourth ventricle (foramen of Luschka) axial iamge