Development of the human cerebellum observed with high-field-strength MR imaging.

A retrospective study of 160 pediatric subjects, aged 32-410 weeks after conception, was conducted to determine the normal developmental patterns of the human cerebellum by means of magnetic resonance (MR) imaging. On the basis of axial T2-weighted spin-echo images (repetition time, 3,000 msec; echo time, 120 msec), which provided the best contrast between gray matter and white matter, five distinct developmental stages were defined. At term, the medial lemnisci as well as the parasagittal cerebellum were myelinated. The appearance of myelin in the middle cerebellar peduncles and the basilar pons preceded that in the corpus medullare of the cerebellum. The normal age ranges for the different stages were defined with statistical analysis. These ranges are applicable to the daily routine of image interpretation. The sequence of myelination in the cerebellum observed at MR imaging correlates with the known patterns observed in pathologic studies but lags behind by an average of 6 months.