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

•The human AO are separated into caudal and rostral parts in the fetal period.•The nuclear volume and the neuronal profile areas increase with age.•The neuronal numerical density decreases with age through rapid and slow phases.•The total neuronal number shows a weak correlation with age.•Natural neuronal death may occur at mid-gestation in the AO.