Choroid Plexus Cyst (CPC)

CPC is a round sonolucent in the context of the choroid plexus of lateral ventricles, with a diameter of >2 mm, resulting from CSF and cellular debris accumulating in neuroepithelial folds. It is the most common intracranial abnormality detected antenatally. Most of these cysts are benign and regress spontaneously, however, when associated with other abnormalities, especially in cases of large cysts (>10 mm), bilateralness, and lack of regression after 24 weeks, they are a sensitive marker for trisomy 18 in early second trimester. The cysts (at least in many cases) are in fact pseudocysts exhibiting angiomatous patterns of capillaries in their walls.

Incidence: 1-2% of midtrimester screenings of low-risk pregnancy.

Fig 1: Choroid plexus cysts  Transverse scan of the skull: bilateral large choroid plexus cyst (arrow)

Sonographic findings:

  • Small cyst of <1 cm in diameter (0.3-2.0 cm) within the choroid plexus, commonly located in the posterior of the atria.
  • Because of the changing echo texture of the choroid plexus through gestation, choroid plexus cysts must be at least 2.5 mm in diameter for confident diagnosis before 22 weeks of gestation and at least 2 mm after 22 weeks.
  • Simple cyst with slightly irregular wall but sometimes multiloculated and more complex.
  • Often bilateral.
  • Mostly seen between 15 and 24 weeks of gestation and resolved after this.
  • Associated anomalies, particularly hands abnormalities, when related to chromosome abnormalities.
  • Usually no need for differential diagnosis, however, rarely large CPCs can be  mistaken for ventriculomegaly.

Choroid plexus cyst:  Transverse scan at the level of lateral ventricles: unilateral cystic lesion (*) in the choroid plexus

Choroid plexus cyst:  Transverse scan at the level of lateral ventricles: unilateral cystic lesion (*) in the choroid plexus with mild ventriculomegaly

Choroid plexus cyst:  Transvere scan at the level of lateral ventricles: bilateral choroid plexus cyst (*) with strawberry head shape, associated with trisomy 18

Associations: The risk of chromosomal abnormalities, especially trisomy 18, is about 1-2% when no other anomalies are present and the risk increases to about 1 in 3 if any other associated abnormalities are detected antenatally. The risk of Down’s syndrome in fetuses with CPC but no other anomalies detected antenatally is 1 in 880, nearly the same as in the general population. Furthermore, isolated choroid plexus cyst in women of <35 years of age may not increase the risk of trisomy 18.

Management: A careful search for associated anomalies is indicated. If an additional sonomarker including hands is identified, karyotyping should be performed. Isolated CPCs do not alter standard obstetric management.

Prognosis: Good and usually asymptomatic and transient for isolated CPCs, though persistent enlarged CPC need follow-up or even neurosurgical intervention in some cases.

Recurrence risk: Sporadic.