Pathology of the auditory system in autosomal trisomies with morphometric and quantitative study of the ventral...

Anomalies of the peripheral auditory system have been reported in major autosomal trisomies. In order to investigate the central auditory pathway, a quantitative and morphometric study of the ventral cochlear nucleus was performed in 2 cases of trisomy 13, 2 cases of trisomy 18 and 1 case of trisomy 21. Data were obtained using a Cambridge Imanco Quantimet 720 Image Analyzing System according to the methods already described. For statistical evaluation, trisomy 13 and 18 cases were considered as group 1-trisomies and compared to full-term controls. Each trisomy was then compared separately to both premature and full term control groups. Trisomy 21 was investigated separately. Quantitative data in trisomy 18 suggest a slight maturational retardation of the ventral cochlear nucleus with respect to gestational age. No significant abnormalities were detected in trisomy 13, aside from those determined by the age difference, when compared to premature controls. The estimated total number of neurons in both trisomies did not differ statistically from that of the control groups. Other brain stem auditory nuclei did not show relevant pathology. Golgi impregnation of the temporal cortex revealed immature neuronal development, especially in trisomy 13. Trisomy 21 showed a greatly reduced number of neurons in the ventral cochlear nucleus, a small nuclear volume, low cell packing density and an abnormally large mean neuronal diameter. The findings of this investigation are discussed and tentatively correlated to the hearing defects reported in these trisomies.