Reversible porencephaly. Alteration of the cerebrospinal fluid flow after shunt malfunction.

The cases of four infants (five lesions) are reported, where "porencephalic cysts," located along the ventricular catheter after shunt malfunction and Ommaya reservoir insertion, disappeared after ventriculoperitoneal (VP) shunt revision and combined cyst peritoneal (CP) shunt, or after VP shunt alone. This pathological state is thought to be a rare postoperative complication. Its pathogenesis and therapy are discussed. Shunt malfunction or Ommaya reservoir insertion may result in a hypertensive hydrocephalic state. Cerebrospinal fluid (CSF) flows out through a catheter penetrating the site of the ventricular wall and expands in the surrounding white matter to form a porencephalic cavity. Once this porencephalic state occurs, it will not disappear spontaneously because the CSF flows in one direction. As treatment for closed porencephaly, CP shunt following a VP shunt revision was markedly effective; for communicating porencephaly, a VP shunt revision alone was effective.