Morphology of hindbrain neuronal complexes in human fetuses of 17-18 weeks of intrauterine development

Congenital defects of the central nervous system (CNS) are one of the most common causes of death and disability in newborns. Therefore, it is extremely important to assess the development of the fetal CNS in the intrauterine period in time to identify any changes in its development and give appropriate advice to parents on pregnancy support, offer options for fetal therapy and type of delivery, as well as postpartum treatment and prognosis. The aim of our research was to determine the morphological features of the neural complexes of the human fetal hindbrain at 17-18 weeks of fetal development, the size and area of the cranial nerve nuclei in the region of the pons and the cerebellar nuclei. In a research study we used biological material obtained from the Vinnytsia Maternity Hospital after a termination of pregnancy in a healthy women for medical reasons, due to fetal chromosomal abnormalities not related to CNS developmental defects. The material for anatomical and histological examination were human fetuses with a gestation period of 17-18 weeks. The fetus`s weighed 250.8±14.5 g, and the parieto-coccygeal length were 163.3±8.4 mm. The researched tissue samples of hindbrain were fixed in a 10 % solution of neutral formalin, and then sections of 8-9 μm thick celluloid blocks were prepared for further histological examination. The preparations were stained with hematoxylin-eosin, toluidine blue according to the Nissl modification. For the statistical analysis of digital data Microsoft Excel 2016 and Statistica 6.1 were used. The normality of the distribution was assessed using the Shapiro-Wilk test, histograms were constructed for data visualization, and the standard deviation and variance of the samples were calculated. Histograms were constructed to visualize the data, the standard deviation and sample variance were calculated. The microscopic examination of the cerebellum revealed the outer granular, molecular, inner granular, intermediate, and ventricular layers. The presence of cerebellar nuclei, which were located in the intermediate layer, was also established. On the cerebellar section, the dentate nucleus was visualized as a thin curved line with its convex side directed laterally and dorsally. The abducens nucleus is located ventrally to the dorsal surface of the pons, laterally to the medial longitudinal fascicle. The facial motor nucleus is located medially to the abducens nucleus and has an elongated shape with indistinct borders. The trigeminal motor nucleus is laterally to the facial nucleus, has indistinct borders, a rounded shape, and consists of neurons at different maturation stages. In the lateral part of the pons is the vestibular nucleus, which has an irregular oval shape; the borders of the nucleus are indistinct. Also, below the vestibular nucleus, laterally, there is a cochlear nucleus, without clear contours, oval elongated shape. Thus, іn the posterior part of the brain at 17-18 weeks of fetal development, the nuclei of the abducens, trigeminal, facial, and vestibulocochlear nerves located in the pons. Dentate, globose, emboliform and fastigial nuclei also were found in the cerebellum.