Accelerated maturation of the adrenal medulla in anencephaly

A review of the pathologic features at autopsy of patients with anencephaly indicated the possibility of an accelerated maturation of the adrenal medullary tissue. The histologic features of the adrenal glands from 50 patients with anencephaly and 50 nonanencephalic infants matched for gestational age who had undergone autopsy at the Johns Hopkins Hospital were therefore examined. The cells of the adrenal medulla showed progressive maturation during fetal life from neuroblastic cells, to larger cells with increased cytoplasm, to still larger cells with vacuolated cytoplasm and a positive chromaffin reaction. Each anencephalic infant was compared to its matched control to determine which had the greater maturation of medullary cells. In 35 instances (70%) the adrenal medulla of the anencephalic infant was judged to be more mature than its control, in 13 (26%) the maturation was equal, and in 2 (4%) the anencephalic infant was less mature (p less than 0.001). Although the data were not subject to quantitation in this retrospective review, it appeared that the anencephalics also had greater amounts of medullary tissue than controls. The explanation for accelerated maturation of the adrenal medulla in anencephaly is not known. It is possible that the proximity of the definitive cortex to the medulla, resulting from atrophy of the fetal cortex, may accelerate medullary maturation by producing a different local corticosteroid milieu.