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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.

SCALP

Three scalp lesions may produce macrocephaly. They are caput succedaneum, subgaleal hemorrhage, and cephalohematoma. They produce significant head asymmetry.

Caput Succedaneum
Caput succedaneum is due to edema between the skin and the epicranial aponeurosis. It presents as a mass, usually located in the vertex, that crosses the sutures and extends over several bones. The mass is soft, superficial, and pitting. The edema results from compression of the scalp by the uterus or suction on the scalp if a vacuum extractor was used during delivery. More about it... 106

Subgaleal Hemorrhage
Subgaleal hemorrhage is due to blood between the epicranial aponeurosis and the external periosteum. Subgaleal hemorrhage presents as an evenly spread mass throughout a large portion of the scalp (Figure 284.1). The mass is firm, fluctuant, crosses suture lines, and increases in size after birth (sometimes at an alarming speed).

Figure 284.1.Computed tomography of the brain (axial) at different levels demonstrates subgaleal hemorrhage.

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.

Figure 284.2.Scout film for CT of the brain demonstrates subgaleal hemorrhage extending to the neck.

 

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