Bone regrowth and recurrence of symptoms following decompression in the infant with Chiari II malformation.

The Chiari malformation is the leading cause of death in infants with myelodysplasia. While controversial, early operative decompression may halt or reverse the progression of symptoms. If symptoms recur after initial improvement, attention is directed to assuring shunt patency and the absence of hydromyelia and not to reassessment of the area of bone decompression. Three infants are presented who initially improved after Chiari decompression only to have recurrence of symptoms several months after surgery. In each case, regrowth of bone at the site of previous decompression was documented radiographically and at surgery. In one case, regrowth of bone occurred twice. Each child stabilized or improved following further decompressive surgery. A theory of bone regrowth and a possible means of prevention are discussed. If recurrence of Chiari symptoms occurs after decompressive surgery in infants, thin section CT with bone windows through the operative site should be performed to exclude bone regrowth and recurrent compression.