MRI Seen Valuable in Forecasting Premature Babies' Future

CHRISTCHURCH, New Zealand, Aug. 17 -- For preterm babies born at 30 weeks or earlier, MRI can help foretell future developmental deficits better than standard ultrasonography, according to researchers here.

Neonatal MRI may improve the ability to intervene early with the children who need it most, reported Lianne J. Woodward, Ph.D., of the University of Canterbury here, and colleagues, in the Aug. 17 issue of the New England Journal of Medicine.

"A major issue confronting clinicians who work with preterm infants and their families is the identification of infants who are most at risk for subsequent neurodevelopmental disability and who may benefit from early intervention services," the investigators wrote.

They found that moderate-to-severe white matter abnormalities, as seen on MRI, significantly predicted later severe motor delay and cerebral palsy. Their conclusions came after adjusting for a wide range of factors including neonatal ultrasound findings.

Conversely, grey matter abnormalities as well as ultrasonographic findings of grade III or IV intraventricular hemorrhage, periventricular leukomalacia, or both, were not significant predictors of later deficits, after adjusting for MRI findings.

The researchers found that moderate-to-severe white matter abnormalities on MRI predicted at age two years:

• A 3.6-fold increase in cognitive delay (95% confidence interval [CI]: 1.5 to 8.7).
• A 10.3-fold increase in the risk of motor delay (95% CI: 3.5 to 30.8).
• A 9.6 times greater risk of cerebral palsy ((95% CI: 3.2 to 28.
• A 4.2 times greater risk of neurosensory impairment (95% CI: 1.6 to 11.3).

One in five children's cognitive score was at least six months below their age level corrected for gestational age. About one in four had mild psychomotor delay and 10% severe. Ten percent 10% had cerebral palsy, 5% had hearing problems and 7% had vision problems.

Still, "a substantial proportion of children with moderate-to-severe white matter abnormalities were free of severe impairment at two years of age," Dr. Woodward and colleagues wrote, underscoring that "worrisome MRI findings may not necessarily result in severe neurodevelopmental problems."

The investigators studied 167 infants born at 30 weeks gestational age or less in New Zealand and in Australia. They received standard cranial ultrasonography at specified times within six weeks of birth.

At what would have been term for each baby, it was fed, wrapped and placed unsedated in a beanbag in the MRI scanner. While 28% of the infants had no white matter abnormalities and 51% had no grey matter abnormalities on the MRI, most did have white matter abnormalities (51% mild, 17% moderate, and 4% severe).

Two independent MRI readers scored the nature and extent of white-matter abnormality, loss in volume of periventricular white matter, as well as the extent of cystic abnormalities, ventricular dilation, and thinning of corpus callosum. Grey matter abnormalities were graded for extent of signal abnormality, quality of gyral maturation, and size of subarachnoid space.

Although MRI offers better spatial resolution for imaging, the need to modify equipment to accommodate small infants and accompanying needles, monitoring equipment, and ventilators have been barriers to adoption of MRI for them.

At around their second birthday, the children were given a battery of cognitive, sensory, and motor tests.

After adjustment for a variety of possible confounding factors including abnormalities found by ultrasonography, MRI still significantly predicted subsequent risk of severe motor delay and cerebral palsy.

The researchers reported "reasonable specificity" of MRI (82% to 89%) at identifying abnormal results and "high" sensitivity of moderate-to-severe abnormalities on MRI for later neurodevelopmental outcomes.

In a related editorial, Olaf Dammann, M.D., of the Hannover Medical School in Germany, and Alan Leviton, M.D., of Children's Hospital in Boston and Harvard, suggested that the extra expense and assessment of only one additional component of brain function beyond ultrasound make it premature to use MRI routinely for these fragile infants.

They pointed out that the authors combined grade III and grade IV intraventricular hemorrhage into a single category. This may have had the effect of inclusion of children who did not have white-matter damage into this category which is likely to have magnified the superiority of MRI over ultrasound in the prediction of subsequent impairment.

Drs. Dammann and Leviton also wrote that it would be helpful to clinicians to have more information about the positive and negative predictive values of the MRI findings.

As questions about the future are among the most pressing for parents and caregivers of extremely preterm babies, sometimes the best approach in the face of limited predictive tools is simply to "offer the equivalent of, 'Take them home, give them lots of love, and let's see how things go,'" Drs. Dammann and Leviton suggested.