enlargement occurs in neurocutaneous disorders, Soto syndrome, metabolic
megalencephalies, and some degenerative disorders.
The possibility of a neurocutaneous
disorder should be considered in every neonate with macrocephaly. The
evaluation of every neonate with macrocephaly should include a careful
cutaneous examination. The two neurocutaneous disorders most often associated
with macrocephaly are hypomelanosis of Ito and linear nevus sebacceous
with Soto syndrome are born with borderline macrocephaly. The diagnosis
of this disorder is established by the presence of a growth spurt beyond
the normal range during the first 3 years of life. This excessive growth
spurt causes the infant to become larger than normal, especially the head.
Plasma somatomedin levels are usually elevated during the growth spurt.
Soto syndrome is usually a sporadic condition, although familial cases
have been reported. Estrogen may reduce growth in girls.
megalencephalies do not usually present in the neonatal period. The exceptions
to this are glutaric acidemia type I, Canavan disease, and Alexander disease.