Cerebral Magnetic Resonance Imaging (MRI) and Mental and Motor Function of Very Low Birth Weight Infants at One Year of Corrected Age

Abstract

Thirty-one (77.5 %) of a year cohort of 40 surviving infants with birth weight < 1500 grams were seen on follow-up examination at one year of corrected age. At neurological evaluation 20 infants were normal (Group 1), seven infants were considered at risk (Group 2), and four infants had cerebral palsy (Group 3). Assessment on the Bayley Scales gave significantly lower mean scores in Group 3 compared with Group 1, both on the Mental Index (63 versus 102, p < 0.001) and on the Psychomotor Index (PDI) (60 versus 94, p < 0.005). Mean PDI score in Group 2 was significantly lower than in Group 1 (74 versus 94, p < 0.005). Cerebral MRI was performed in 27 infants. Of the 19 infants in Group 1 examined with MRI, 14 infants showed deviating changes in both myelin deposition and maturation (2). In all 14 infants the central occipital white matter was affected and in three infants also the centrum semiovale, both areas correspond to predilection sites for periventricular leukomalacia (PVL). Five infants had irregular shape of the occipital horns of the lateral ventricles. These findings may also represent the end stages of PVL (4). Only four out of seven infants were examined with MRI in Group 2. However, three infants had deviating myelination and three had irregular shape of the posterior horns. In Group 3 all infants were examined with MRI and all had deviating myelination and irregular and slightly dilated posterior horn. There was a significant correlation between abnormally dilated occipital horns seen with MRI, and cerebral palsy and low scores on the Denver and the Bayley tests. Infants with hypointense white matter areas in the centrum semiovale seemed to be at increased risk of having cerebral palsy. However, all these infants also had dilated occipital horns. Increasing days on mechanical ventilator and lower gestational age were both significantly correlated with an increasing number of areas with deviating myelination seen on MRI.