CAUSES OF MACROCEPHALY
Smith’s book of recognizable patterns of human malformations lists macrocephaly as a frequent finding in 27 syndromes and as an occasional finding in 16 more. Macrocephaly during the neonatal period results from enlargement of any component or “space” of the head. The components or spaces of the head most likely to enlarge are the scalp,skull, subdural space, subarachnoid space, brain parenchyma, intraparenchymal vessels, and ventricles.
Subgaleal hemorrhage may extend to the neck or the face (Figure 284.2). It is caused by bleeding that results from linear skull fracture, suture diastasis, or fragmentation of the superior margin of the parietal bone. Coagulation problems may contribute to the bleeding. Subgaleal hematoma may lead to anemia and hyperbilirubinemia. Anemia may be severe enough to require blood transfusion or may even cause death. The volume of blood required may be estimated using the following formula: 38 milliliters for each centimeters by which the actual head circumference exceeds that expected or known. If the head circumference at birth was 35 centemiters and 3 hours later it is 40 centimeters then multiply 5 (40 minus 35) by 38 to find the volume of blood required.