Normal gyration and sulcation in preterm and term neonates: appearance on MR images.

PURPOSE: To provide a practical standard for normal development of gyri and sulci in preterm and term neonates. MATERIALS AND METHODS: Thirty-nine living preterm infants without substantial neurologic problems underwent magnetic resonance (MR) imaging of the brain. Five infants who were born at term but died of a nonneurologic disorder within 1 week and who underwent autopsy were examined after death with MR imaging. Seven cerebral surface areas were defined, and the development of gyri and sulci in each area was assigned a score between 1 and 5. RESULTS: The postconceptional age (PCA) range of the newborns was 30-42 weeks. When the gyral development scores were assessed as a function of PCA, four transition points could be discerned for the brain as a whole; these transitions occurred at PCAs of 32, 34, 37, and 40 1/2-41 weeks. These four transition points allowed the general gyral development to be divided into five stages. Development of gyri and sulci was most advanced in the area of the central sulcus and the medical occipital area. Development was latest in the frontobasal and frontopolar areas and the anterior part of the temporal lobe. CONCLUSION: A simple staging system allows easy assessment of the progress of cerebral gyration and sulcation in preterm and term infants.