DEVELOPMENT OF THE HUMAN PRINCIPAL SENSORY TRIGEMINAL NUCLEUS - A MORPHOMETRIC ANALYSIS

The anatomical development of the principal sensory trigeminal nucleus was assessed with morphometric features using serial celloidin sectio ns of 15 human brains, including 12 brains obtained from fetuses and n eonates. A microscope and an optical electronic planimeter combined wi th a computer were employed for morphometric measurements of columnar areas, neuronal numbers, neuronal areas and neuronal perimeters to sta tistically analyze and evaluate the development of neuronal densities, neuropil indexes and circularity ratios. We could not detect the prin cipal sensory trigeminal nucleus in the specimen of 12 gestational wee ks (GW). Microscopic observation disclosed that the fetal principal se nsory trigeminal neurons approached those of the adult around 33 GW in terms of cell arrangements, amounts of Nissl bodies and morphology of neurons. Our morphometric analysis showed that the columnar volume, t he neuronal area and the neuropil index increased with gestational age . The neuronal density decreased with gestational age, especially from 16 to 32 GW. Comparing the neuronal area with the columnar volume, it developed before the columnar volume during the fetal period. The neu rons of the principal sensory trigeminal nucleus matured around 33 GW under microscopic observation and in terms of the distribution of neur onal areas. The development of the neuropil may accelerate after indiv idual neurons of principal sensory trigeminal nucleus mature. (C) 1997 Elsevier Science Ireland Ltd.