ULTRASOUND OF THE CHOROID PLEXUS  

 

6-7 weeks: Choroid plexus present but not yet visualized.
8 weeks: Choroid small and echogenic.
9 weeks: Can be constantly seen on both sides of the falx within the lateral ventricles. It becomes the most dominant intracranial structure in the late first trimester cranium.
9-11 weeks: Choroid fills the entire lateral ventricle.

 

7 weeks

8 wks

10 wks

12.5 wks

 

12 weeks: Size appears to decrease (due to increased cortical growth of the brain).

  • Best seen in the atria of the lateral ventricles.
  • Attached at the Foramen of Munroe.

  • Posterior contour is smooth.
  • Telia choroidea = thin choroid plexus layer covering the thalami and extending into the lateral ventricles.
  • Choroid plexus of the 4th ventricle is difficult to image.

 

 

 

NORMAL VARIANTS  

- DOUBLE CHOROIDAL PATTERN OR BIFID CHOROID PLEXUS

 

 

The neonatal choroid plexus may have various sonographic appearances (1).

A double choroidal pattern may present as a separation of the two portions (completely or incompletely), with the medial one simulating a dangling choroid plexus (2).

The differential diagnosis is an interventricular hemorrhage which usually changes the smooth surface of the choroids.

 

 

Bifid choroids plexus

 

 

 

NORMAL VARIANTS  

- THE CALCAR AVIS

 

 

The calcar avis forms the calcarine fissure which develops at 16 weeks of gestation.

The fissure may extend deeply from the medial aspect of the occipital lobe towards the occipital horn of the lateral ventricles. As the fissure elongates, it folds and forms a mound of white matter that indents into the medial surface of the occipital horn, the calcar avis (2,3).

Sometimes it is more prominent, depending on the depth of the infolding at the calcarine fissure. In these situations, since it is isoechoic with surrounding brain tissue, the calcar avis may be confused with a resolving blood clot, particularly on parasagittal scans. The way to differentiate it from an intraventricular clot is to slightly tilt the transducer medially from the cavity of the ventricle. From this view, the calcar avis is properly identified by its continuity with the brain white matter and branches of the calcarine fissure.

 

 

REFERENCES

 

 

  1. Lee Y, Chung H, Hwang H, Yoon M, Lee H. Choroid plexus in normal full-term neonates: sonographic classification and clinical application. Presented at the International Pediatric Radiology Meeting, Boston, May 25-30, 1996; 44
  2. F. F. Correa, C. Lara, J. Bellver, J et.al. An anatomical fetal brain structure and a normal variant mimicking anomalies on routine neurosonographic imaging: report of two cases. Ultrasound Obsytet Gynecol 2004;24:672-674
  3. DiPietro MA, Brody BA, Teele RL. The calcar avis: demonstration with cranial US. Radiology 1985; 156: 363-364.