choroid plexus – cyst

choroid plexus – cyst

choroid plexus cyst
choroid plexus cyst. note the bilateral cysts in the choroid plexuses.

description

the choroid plexus is evident from seven weeks gestation, and is involved in the production of cerebrospinal fluid. within each ventricle, the choroid is represented by an aggregation of neuroepithelial cells, which are especially prominent in the lateral ventricles; by the end of the first trimester, it may occupy most of the developing ventricles, but by the third trimester the relative dimensions have changed so that the choroid is largely confined to the atrium and posterior horn of each lateral ventricle. growth of the choroid is greatest in the second trimester and it is at this stage that cysts are most commonly visualised, thought to represent localised loculation of secretory products.

diagnosis

the finding of round or oval anechoic areas within the choroid plexus is characteristic. they may be single or multiple, unilateral or bilateral, and range in size from 2 – 20 mm. multiple small cysts may give rise to a honeycomb appearance. the incidence of choroid plexus cysts seen on routine sonography ranges from 0.4 to 2.3 per cent, and is most commonly seen in the second trimester. the majority resolve by 24 weeks gestation and are no longer visible on subsequent scans. there is a well documented association with trisomy 18, with 30% of affected fetuses demonstrating choroid plexus cysts; other reported karyotypic abnormalities include trisomy 21, 46xy-14,+t(14;21), triploidy (69 xxx) and klinefelterís syndrome (xxy). most of these display the other abnormal sonographic features, and this is especially true of trisomy 18 (growth restriction, ventricular septal defects, fixed flexion deformities of the hands, radial aplasia, micrognathia, rockerbottom feet). associated abnormalities in chromosomally normal fetuses are not common, and include pyelectasis, omphalocele and hydrocephalus. conversely, the incidence of karyotypic abnormality in the presence of isolated choroid plexus cysts is 1.2 per cent (95% confidence intervals 0.87-1.57). there is no correlation between this and the size, number, or eventual resolution of cysts that are observed on sonography, and this should be borne in mind when counselling. a large multicentered study is required to determine conclusively the association between choroid plexus cysts and trisomies 18 and 21. the most recent recent study publication on the significance of choroid plezus cysts in an unselected population (chitty et al. 1998) concludes that the presence of choroid plexus cysts increases the risk for aneuploidy, mainly trisomy 18, but the final risk remains increasing with maternal age.

differential diagnosis

the intraventricular location of the cysts, and the contrasting nature of surrounding choroid make this diagnosis straightforward in the second trimester, but a resolving intraventricular haemorrhage may present as a multicystic mass; associated ventriculomegaly would be expected in this situation. a choroid plexus papilloma may also have cystic regions, but the surrounding tissue would be more echogenic than normal choroid, and serial scans may show progressive enlargement of the lesion. large choroid plexus cysts may be mistaken for ventriculomegaly.

sonographic features

anechoic cysts of 2 to 20 mm size.

commonest between 15 and 26 weeks gestation.

single or multiple, unilateral or bilateral.

located in posterior aspect of lateral ventricles (at level of atria).

associated syndromes

  • none

references

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