Risk Factors, Causes and Prevention of Periventricular Leukomalacia (PVL), 6/1997

A research study published in the journal Developmental Medicine and Child Neurology¹ explores the risk factors associated with the occurrence of periventricular leukomalacia (PVL), one of the most important pathological changes in the premature infant's brain that causes cerebral palsy.

Periventricular leukomalacia (PVL) is a nerve fiber tract degeneration -- leukomalacia -- around the cavities in the center of the brain filled with cerebrospinal fluid -- periventricular. The degeneration can destroy neural communication pathways between several areas of the brain and/or between the brain and the spinal cord. Cerebral palsy is a major consequence of this destruction.

The study demonstrates that the period of greatest risk for the occurrence of PVL is between the 27th-30th weeks of fetal development, peaking at the 28th week. The full period of pregnancy is 40 weeks; thus the PVL damage occurs most often late in the second trimester or early in the third trimester of pregnancy.

The most frequent events associated with PVL during this highly sensitive period are:

• Intrauterine infection, affecting the membranes surrounding the infant;

• Premature rupture of the membranes;

• A combination of both (the most common occurrence associated with PVL).

The underlying factor is usually an infectious process in the mother's uterus. The infection releases toxins affecting the membranes surrounding the fetus and also selectively injuring sensitive areas of the developing brain. Not only do these toxins affect the fetal brain, but they may also be responsible for the premature rupture of the membranes and premature birth of the baby.

Thus, an important period of risk to the fetal brain and a potential cause of PVL are being identified.

Comment

Evidence continues to accumulate pointing to intrauterine infection as a very important reason underlying premature delivery, fetal brain damage due to PVL, and the occurrence of cerebral palsy. The mother is often not aware of the infection and usually presents no symptoms of being "ill". The issue is how to detect this sub-clinical infection and identify the specific organism(s) responsible for it. Doing elaborate tests on all women at 5-7 months of pregnancy searching for a potential infection is not a practical answer. A "screening" method needs to be available which would alert mother and doctor that more elaborate testing is indicated. A number of investigators are exploring the development of a practical method of screening. Also, investigators are studying why these subclinical infections cause PVL. The objectives are to identify pregnant women at risk of having a subclinical intrauterine infection, provide therapy and prevent PVL -- eliminating a major cause of cerebral palsy occurring during pregnancy, but prior to delivery.

¹Zupan, V et al. Periventricular Leukomalacia: Risk Factors Revisited. Developmental Medicine and Child Neurology 38:12: 1061-1067 (1996).