Cerebral palsy: earlier origins.

Cerebral palsy: Earlier origins

Researchers, it now appears, know less than they thought they did about cerebral palsy. While conventional wisdom has linked the neuromotor disorder to traumas suffered during birth, a new report suggests that the path towards the disabling and sometimes fatal syndrome is most often taken closer to the time of conception. Though the finding, reported in the July 10 NEW ENGLAND JOURNAL OF MEDICINE, undercuts hopes for obstetric "saves,' knowing what they don't know may redirect researchers and physicians.

The idea that cerebral palsy can be traced to circumstances during birth--to a lack of oxygen, for example--has held favor for more than a century, supported by studies that retrospectively looked for causes of specific cases. But this is the first time that researchers have looked at a random sampling of births (more than 50,000 of them, at 12 hospitals) to see if the apparent associations hold up.

Karin Nelson and Jonas Ellenberg of the National Institute of Neurological and Communicative Disorders and Stroke, in Bethesda, Md., looked at prepregnancy risk factors such as maternal retardation, as well as variables during pregnancy (such as drugs taken) and delivery. None of the factors accounted for a large share of the cerebral palsy cases. Even when the researchers grouped together the "best' risk factors, the combination failed to predict nearly two-thirds of the cases of cerebral palsy, and the "overwhelming majority' of children determined by these factors to be at highest risk did not in fact have the syndrome. "We probably do not know what causes most cases of cerebral palsy,' the researchers conclude.

Because problems during labor and delivery did not turn out to be important predictors of cerebral palsy, the researchers say that it now seems that abnormalities of delivery often are markers of earlier brain damage--with roots perhaps as early as conception--rather than causes of it. The finding is in some ways discouraging, as it means that interventions at delivery come too late to help. But it does explain why increasingly sophisticated obstetric techniques have had little impact on the frequency of cerebral palsy. It may also help to stem the malpracties suit-spurred flight of obstetricians from practice, Ellenberg says. "The reason that obstetricians are successfully sued is . . . that [people] go back and look for problems in the delivery,' he says. "You're always going to find something that went wrong. . . . But if you eliminate all the risk factors you would not eliminate cerebral palsy.'