Of or relating to a disease, or condition, that is not congenital but develops after birth.

Any hydrocephalus which appears in adulthood from any cause, including head injury, stroke, meningitis, or unknown cause (idiopathic).

A blockage or narrowing of the pathway from the third to the fourth ventricle.

Resembles a cobweb membrane which covers the brain and spinal cord.

See Arachnoid Granulations.

Protrusions of the arachnoid membrane of the brain. The arachnoid villi (or granulations) are very similar to a one-way valve, as they allow the CSF to drain from the subarachnoid space into the superior sagittal sinus, where it can be reabsorbed into the blood system.

Where the arachnoid extends between the two temporal lobes.

(Also referred to as External Hydrocephalus.) An accumulation of CSF found on the outside of the brain, which usually presents itself at birth or soon thereafter. The child’s head size will increase, but scans show no internal problems in the ventricles or pathways. The condition usually corrects itself within about 18+ months of age.

Small, flexible tube (part of the shunt system) inserted into the body part (i.e. ventricle), which allows the passage of the Cerebrospinal Fluid.

The clear water-like fluid that bathes the brain and spinal cord. The fluid provides nourishment, carries away any debris (such as excess protein cells), and protects us from injury. It is in constant production, circulation and absorption. The body makes almost a pint of CSF daily.