Development of the human cerebellum from midgestation to the perinatal period: A morphological study

The human cerebellum has large hemispheres (HS) and develops slowly over the pre- and postnatal periods. Several morphological studies have reported regional differences during the fetal period. This study aimed to investigate these differences by evaluating serial brain sections.

Ten cerebellar samples aged 21-43 postmenstrual weeks (PW) were analyzed. Horizontal serial sections were cut and stained using the Klüver-Barrera method. After microscopic observations, a volumetric analysis was performed for the cerebellar cortex and medulla among the HS, vermis (VM), and flocculus (FL).

The lamina dissecans (LD) was more prominent and lasted longer in the HS than in the VM and FL. The maturation of Purkinje cells and the accumulation of granule cells in the internal granular layer started earlier in the latter than in the former. Cortical differentiation was most delayed in the inferior semilunar and tonsillar lobules. Volumetric analysis showed that volume increased more in the HS than in the VM and FL after midgestation, and that it increased more intensively in the cortex than in the medulla in each region.

The human cerebellar cortex may develop through three stages in fetal period: (1) three-layers stage (before 20 PW); (2) five-layers stage (20-30 PW); (3) four-layers stage (after 30 PW). Particularly, the second stage is characterized by a transient appearance of the LD, which is most evident in the HS. Regional differences should be carefully considered when interpreting morphogenetic data.