THE PROBLEM of cranium bifidum is not nearly so well described in the literature as that of spina bifida, principally because the occurrence of the former is so much rarer than that of the latter. However, Ingraham and Swan1 were able to amass 84 cases and other reports which indicate that cranium bifidum in its own right is not an inconsiderable problem. The occurrence of hydrocephalus associated with these cranial defects is generally thought to be high. Bucy2 states that these cranial malformations are frequently associated with hydrocephalus. On the other hand, Ingraham and Swan mention only 4 instances of increasing hydrocephalus in 35 cases with operation. On the whole, however, general medical opinion agrees with Bucy that the incidence of this complication is high.
The cause of hydrocephalus in the case of spina bifida has long been recognized in the Arnold-Chiari complex. The mechanism of the same