Histomorphometry of the cortical layers and the dentate nucleus of the human fetal cerebellum

Objectives: This study was aimed at determining the histomorphometry of the cerebellar cortical laminae and the dentate nucleus of the human fetal cerebellum; the number and shape of the neurons; and the gestational age of appearance of the cerebellar folia, white matter and arbor vitae cerebelli. Methods: Microscopic sections of the human fetal cerebellum stained with hematoxylin and eosin and Bielschowsky silver stain were studied. Results: The thickness of the cortical laminae of the human fetal cerebellum varied among gestational weeks as follows: external granular layer: 36.06 ± 9.36–50.05 ± 34.06 μm, molecular layer: 32.76 ± 17.16–52 ± 28.6 μm, Purkinje cell layer: 9.36 ± 6.8–15.6 ± 4.68 μm and internal granular layer: 66.65 ± 24.42–146.63 ± 47.79 μm. Similarly, the number of neurons per field of view at 1000X under a compound microscope varied among gestational weeks as follows: external granular layer: 89.92 ± 42–142.84 ± 50, molecular layer: 15 ± 12.5–25 ± 8.25, Purkinje cell layer: 3.5 ± 1–5 ± 2.5 and internal granular layer: 98.5 ± 69.75–224 ± 47. White matter in the fetal cerebellum was already present at the age of 12th gestational week, whereas cerebellar folia appeared at 16–20 gestational weeks. Arbor vitae cerebelli and the dentate nucleus became conspicuous after the 20th gestational week. Fetal neurons were round except for Purkinje cells. Conclusions: The thickness and neuronal counts of the human fetal cerebellar cortical layers and the measurements of the dentate nucleus along with other histomorphological features varied with gestational age from the 12th week of gestation until birth.