Specific Imaging Findings

Choroid plexus cysts are most frequently located in the trigones of the lateral ventricles, but can occur throughout the ventricular system. They are typically less than 1 cm in diameter and are round or ovoid in shape. On CT, choroid plexus cysts usually demonstrate CSF density but can occasionally appear hyperdense relative to the CSF. The rims of the cysts may contain calcification. On T1- and T2-weighted images, choroid plexus cysts usually exhibit signal similar to that of CSF and may be difficult to identify. Post-contrast imaging may show a sharply marginated rim of peripheral enhancement, particularly in adults. On FLAIR images, cyst contents are often hyperintense relative to the CSF. Around two-thirds of choroid plexus cysts will be very bright on DWI and hence much easier to detect. Choroid plexus cysts are also seen in approximately 1% of fetal ultrasounds in the second trimester and some may persist into the neonatal period.

Pertinent Clinical Information

Choroid plexus cysts are extremely common, occuring in over half of individuals in serial autopsy studies with a similar incidence across all age groups. Most choroid plexus cysts are completely asymptomatic; however, in rare instances, when large or strategically located in the third ventricle they can cause symptoms of acute hydrocephalus due to obstruction. The prevalence of choroid plexus cysts on prenatal ultrasound is increased in fetuses with trisomy 18 (and with some other abnormalities). It has been suggested that identification of cysts which are > 1 cm in size, irregular, bilateral, or in mothers of advanced age should trigger a careful search for additional structural abnormalities.