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Topic

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Choroid plexus

The choroid plexus is a highly vascularized structure composed of ependymal cells, connective tissue, and capillary networks that protrude into the ventricular system of the brain. It is present in the lateral ventricles, third ventricle, and fourth ventricle, where it plays a vital role in cerebrospinal fluid (CSF) production, regulation, and homeostasis. The choroid plexus also forms part of the blood–CSF barrier, selectively filtering blood components to maintain the chemical environment necessary for proper neuronal function.

In addition to CSF secretion, the choroid plexus contributes to immune surveillance in the CNS by hosting immune cells and producing growth factors and signaling molecules.

Synonyms

  • Ventricular choroid plexus

  • CP

  • Plexus choroideus

Function

  • Produces the majority of cerebrospinal fluid (CSF)

  • Maintains blood–CSF barrier, regulating transport of nutrients and waste

  • Contributes to immune and metabolic regulation of the CNS

  • Provides a surface for exchange of ions and molecules between blood and CSF

MRI Appearance

T1-weighted images:

  • Choroid plexus appears as isointense to slightly hypointense compared to brain parenchyma

  • Intraventricular location makes it distinguishable within CSF-filled ventricles (CSF appears dark on T1)

T2-weighted images:

  • Appears isointense to slightly hyperintense relative to gray matter

  • CSF is bright, making the plexus stand out as a denser structure inside the ventricle

T1 Post-Contrast (Gadolinium-enhanced):

  • The choroid plexus shows intense, homogeneous enhancement due to its rich vascularity and fenestrated capillaries

  • Normal enhancement should be symmetric; asymmetric or nodular enhancement may indicate tumor (choroid plexus papilloma, carcinoma), inflammation, or metastasis

MRA (Magnetic Resonance Angiography):

  • Not routinely used for choroid plexus itself, but may demonstrate feeding arteries (e.g., choroidal arteries) in selected cases

CT Appearance

Non-contrast CT:

  • The choroid plexus appears as soft tissue density within the ventricles

  • Often demonstrates physiological calcification, especially in the atrium of the lateral ventricles (glomus choroideum), more common with aging

  • Calcifications appear as hyperdense foci

Contrast-enhanced CT:

  • Choroid plexus enhances brightly and homogeneously due to high vascularity

  • Abnormal enlargement or irregular enhancement suggests tumor, inflammation, or metastasis

MRI images

Choroid plexus coronal

MRI images

Choroid plexus MRI sagittal image

MRI images

Choroid plexus