Porencephaly Health Article

Definition

Porencephaly is a rare condition in which fluid-filled hollows or cavities develop on the surface of the brain. These cavities usually form at sites where damage has been caused by infection, loss of blood flow, or stroke during brain development, but may also be genetic in origin. Equivalent terms are cerebral porosis, perencephaly, porencephalia, and (no longer in favor) polyporencephaly. The prefix "por" comes from the Latin porus, for hole or cavity.

Description

In porencephaly, large dimples, craters, or clefts develop on the surface of the brain. These cavities or cysts are filled with fluid and lined with smooth tissue. They are usually caused by injuries to the fetal or newborn brain before full development of the convolutions or gyri (singular gyrus) on the surface of the cerebrum, especially by infection, ischemia (reduction of blood flow through a vessel), infarction (blockage of blood flow through a vessel), or stroke (bleeding in the brain). The cerebral gyri develop abnormally around a porencephaly cavity, both anatomically and microscopically, and may take on a radiating pattern. Areas of abnormally small gyri (polymicrogyria) may develop on areas of the cerebrum not directly adjacent to a porencephalic cavity.

Porencephaly cavities sometimes develop symmetrically, that is, with a cavity on one side of the brain being matched by a similar cavity on the other side. When a pair of symmetric cavities are very large, they may leave only a thin arch of cerebral cortex running front to back over the top of the brain like a basket handle, a condition termed basket brain. In the most extreme cases, virtually the entire cerebrum may be replaced by fluid, a condition termed hydranencephaly.

Demographics

Porencephaly is rare, and its exact incidence is unknown. A 1984 study from the University of Colorado found in a study of 18,000 patients with seizure disorder

or retarded neural development that 11 had porencephaly, a rate of 1:1650 in that abnormal population.