Evolution of porencephalic cysts from intraparenchymal hemorrhage in neonates: sonographic evidence.

Ninety-four low-birth-weight neonates were screened consecutively with real-time sonography for evidence of cerebroventricular hemorrhage. Among them, 13 were found to have intraparenchymal hemorrhage beyond the area of the germinal matrix. Weekly follow-up sonograms revealed progression to porencephaly in every surviving infant. Four different sonographic patterns were observed during the evolution from the original hemorrhage to the porencephalic cyst. The size of the mature porencephalic cyst correlated directly with the size of the intraparenchymal hemorrhage. After ventriculoperitoneal shunting, the porencephalic cysts became smaller or remain unchanged. One small cyst was no longer identified after successful shunting, but reappeared with shunt failure.