Dendritic arborization in the human fetus and infant with the trisomy 18 syndrome.

Dendritic arborization patterns of visual cortical neurons in four cases of trisomy 18 syndrome were compared with those in 8 neurologically asymptomatic age-matched controls. The trisomy cases included a 20-week-old fetus, a term infant, a 3-month-old infant, and 6-month-old infant. Quantitative Golgi analysis showed a decrease in the mean total dendritic length of apical dendrites in layer 5 pyramidal neurons in the term infant with trisomy 18. In layer 3, an attenuated dendritic tree was observed in the earlier age groups with increased dendritic extent at 6 months. Although not conclusive, due to the small number of subjects, this preliminary study showed definitive dendritic abnormalities in the trisomy 18 syndrome.