[Development of the human facial nucleus: a morphometric study].

The development of the human facial nucleus was studied using complete serial sections of the brains of 8 fetuses at 21, 23, 27, 30, 33, 34, 35, and 40 weeks of gestation, a 2-month-old infant and a 63-year-old adult. Morphometric analysis adopting a microscope, an electronic planimeter and a computer revealed the following three points as to the development of the human facial nucleus. (1) The size of neurons, the amount of Nissl body, the length of processes and neuropil increased gradually after 30 weeks of gestation. (2) The facial nucleus was divided cytoarchitectonically into dorsal, medial, intermediate, ventromedial, ventrolateral and lateral subnuclei at 21 weeks of gestation onwards. The mean neuronal size of the medial subnucleus was smaller than that of other subnuclei. (3) The number of neurons was practically the same regardless of age. At 21 and 33 weeks of gestation, 10% of total neurons was degenerated.