Higher cognitive functions, like language and visual processing, have long been attributed to the cerebrum. But research in premature infants is finding an important role for the cerebellum and shows that cerebellar injury can have far-reaching developmental consequences.
"We've learned that cerebellar injury can cause more than just motor problems," says Catherine Limperopoulos, PhD, in Children's Hospital Boston's Department of Neurology. "We now know to look for it, and can counsel families that their children are likely to experience cognitive, social and behavioral deficits that may benefit from early intervention."
In a study presented this fall, Dr. Limperopoulos and colleagues compared two groups of toddlers. All were born prematurely, but 31 had isolated cerebellar hemorrhage identified at birth, while 31 had normal brain imaging studies. In addition to motor problems, 61 percent of the children with cerebellar injury—versus just 3 percent of controls—had global developmental delays, including deficits in language, visual reception and social/behavioral function.
Cerebellar injury is increasingly diagnosed as more premature infants survive and as neuroimaging techniques improve. Through quantitative MRI studies, published in the March Pediatrics, Dr. Limperopoulos and colleagues found that the cerebellum grows rapidly in late gestation, much faster than the cerebral hemispheres, and that preterm birth arrests this growth. In a review of preterm births at Brigham and Women's Hospital from 1998 to 2002, published in the September Pediatrics, they found a steady rise in the incidence of diagnosed cerebellar hemorrhage, reaching 20 percent among extremely-low-birthweight infants.
The team's latest paper, in the October Pediatrics, suggests that the cerebrum and cerebellum modulate each other's growth and development. Advanced MRI imaging in 74 preterm infants showed that when the cerebrum was injured on one side, the opposite cerebellar hemisphere failed to reach normal size. Similarly, when one cerebellar hemisphere was injured, the opposite cerebral hemisphere was abnormally small.
Limperopoulos raises a caution, however, about fetal MRIs, which have become more advanced but may over-diagnose subtle cerebellar malformations of unclear clinical importance. These findings have caused families undue stress, even though the majority of these children develop normally. "We need to be careful with the way we interpret fetal MRI studies and how we counsel families," she says.
Her team continues to follow children with cerebellar injury. "We want to understand what happens over time," she says. "How the brain adapts and reorganizes after injury may be the best indicator of how a child will do."