Morphometrical Analysis of Developing Cochlear Ganglion Neurons: A Light Microscopic Fetal Study

The cochlear or spiral ganglion neurons are the initial bridge between the external world of sound and its discernment in the brain. As the developing human fetal cochlea is known to start functioning in mid gestational period, its anatomical details when compared with adults could vary with each gestational age. The aim of current study was to assess morphometrical parameter of developing human fetal cochlear ganglion neurons and comparison of data in each gestational period.

Ten aborted human fetuses from 14th to 28th weeks of gestation were procured from Department of Obstetrics and Gynaecology of associated hospital, after obtaining ethical clearance and were processed for studying under light microscope. Area of neurons from each gestational age was measured on histophotomicrographs using image Proplus software. Standard statistical method was used to calculate area range and percentage of small and large ganglion neurons.

The neuronal area increased progressively in successively higher gestation age fetuses. In the fetus belonging to lowest gestational age the area ranged from 4-37μm2 while in highest gestational age fetus its range was 10-58.3μm2. The small ganglion neurons were higher in 14 weeks (65.5%) fetuses and 16-20 weeks (81.03%) fetuses, while in higher gestational age fetuses' large ganglion neuronal population was higher (62-66%).

A baseline morphometrical representation of fetal cochlear ganglion neurons could be of relevance in advanced human experimental studies on effect of neurotrophic factors in human fetuses with congenital deafness. It has been found that these factors directly influence neuronal maturation assessed by progressive increase in soma size and survival.