Absence of connections between spinal nerves and the spinal cord in a twin fetus: a very rare malformation occasionally evidenced at autopsy.

We describe a rare case of spinal cord malformation in a dichorionic diamniotic twin fetus aborted at 20 weeks' gestation due to acute chorioamnionitis with placental dysmaturity probably caused by a maternal viral infection. At autopsy, there were no connections between the spinal nerves and the spinal cord. The spinal cord lacked the posterior median fissure and gray matter; only a few neurons were present in the anterior and lateral gray columns. No chromosome anomalies were found. Although we cannot reconstruct the pathogenetic chain of events leading to this malformation, we believe that it is correlated with a maternal viral infection. We hypothesize that this viral infection altered the delicate balance between the factors inducing and those inhibiting fetal spinal neural differentiation.