DECLINING INCIDENCE OF CENTRAL NERVOUS SYSTEM ANOMALIES IN NEW YORK STATE BY

are the most common of the major structural anomalies of the central nervous system recognizable at birth. Anencephalus is characterized by absence of the cranial vault of the skull. The cerebral hemi-spheres are completely missing or are reduced to small masses attached to the base of the skull. Spina bifida is a dorsal defect of the vertebral column ranging in severity from minor bony defects, visible only by x ray, to massive clefts of the spinal column. Meningocele, meningomyelocele, and myelocele are part of the same embryological process. Congenital hydrocephalus is characterized by enlargement of the head and separation of the cranial bones caused by abnormal production, circulation, or absorption of the cerebrospinal fluid (Potter, 1952). Spina bifida i