occur here, enlarged PVSs may cause obstructive

hydrocephalus. Prominent PVSs also occur in the subcortical

and deep white matter. They are pial-lined, interstitial fluidcontaining structures that tend to occur in clusters of variably

sized cysts. Most PVSs suppress completely; 75% are

surrounded by normal-appearing brain, which helps

distinguish them from porencephalic cysts.

Hippocampal sulcus remnant cysts (HSRCs) are common

normal variants, seen as a "string" of small CSF-like cysts lying

in the hippocampus just medial to the temporal horn of the

lateral ventricle. They are caused by defective or incomplete

fusion of the embryonic cornu ammonis and dentate gyrus

and are of no clinical significance.

Porencephalic cysts are the 3rd most common supratentorial

parenchymal cysts. They may communicate with the ventricles

and are typically lined by gliotic white matter, not ependyma,

and are caused by brain destruction (e.g., peri- or antenatal

insult). The brain surrounding a porencephalic cyst is typically

hyperintense on T2WI and FLAIR.

Periventricular cysts of newborns encompasses a wide,

overlapping variety of periventricular cystic lesions that ranges

from cystic periventricular leukomalacia to connatal and

germinolytic cysts.

Neuroglial cysts, sometimes called neuroepithelial cysts, are

benign glial-lined cavities buried within the cerebral white

matter. Although they can occur anywhere, the frontal lobe is

the most common site. They tend to be solitary, whereas PVSs

are usually collections of multiple cysts of different sizes. A

choroid fissure cyst is a neuroglial cyst that occurs anywhere

along the infolded choroid fissure. Most are found medial to

the temporal horn of the lateral ventricle. HSRCs occur when

there is incomplete fusion of the cornu ammonis and the

dentate gyrus. HSRCs are often multiple, appearing like a

string of small CSF-containing cysts along the lateral margin of

the hippocampus.

Supratentorial intraventric