Development of the human accessory olivary nuclei: A morphometric and computerized 3D-reconstruction study

Abstract

IntroductionThis study described the prenatal development of the accessory olivary nuclei (AO) in humans. Materials/methodsSerial brain sections from ten pre- and full term infants aged 21–43 postmenstrual weeks (PW) were stained using the Klüver–Barrera method. A computerized 3D-reconstruction technique and morphometry were adopted for the study. ResultsThe medial AO (MAO) and dorsal AO (DAO) were identified at 21 PW. The dorsal cap was clearly differentiated from the main body (MB) of the MAO in neuronal cytoarchitecture. Pyknotic neurons were diffusely observed in the AO at 21 PW and were most concentrated in the MB. These neurons became infrequent from 28 PW onward. Neuronal nests existed in clusters between the AO and the medial lemniscus at 21 PW, which reduced progressively in size and number with age. The 3D-reconstructions showed that the AO are separated into caudal and rostral parts, and that this separation is achieved by mid-gestation in the DAO. Nuclear volume increased exponentially with age in the AO, although the rate of increase was half that of the principal nucleus (PO). Neuronal numerical density decreased rapidly 21–28 PW. The total neuronal number showed a weak correlation with age. The mean neuronal profile area increased linearly with age. ConclusionThe human AO are separated into caudal and rostral parts in the fetal period. The nuclear volume and neuronal profile areas increase with age, although the rate of this increase is lower than in the PO. Natural neuronal death may occur at mid-gestation in the AO.