POSTERIOR-FOSSA DECOMPRESSION WITHOUT DURAPLASTY IN INFANTS AND YOUNG-CHILDREN FOR TREATMENT OF CHIARI MALFORMATION AND ACHONDROPLASIA

Some children with Chiari malformation and achondroplasia require post erior fossa decompression that typically includes expansion of the dur al tube with duraplasty. Infants and young children, however, may have a more distensible dura mater than do older patients. Furthermore, th e structures that compress the hindbrain of young patients may be the bone and abnormally thickened atlanto-occipital membrane, i.e., dural band, rather than the dura mater. We have treated 7 children who had C hiari malformation or achondroplasia with posterior fossa decompressio n without duraplasty. All children were symptomatic; 3 had Chiari-I ma lformations, 2 Chiari-II malformations, and 2 achondroplasia. The age range was 3 months to 2.5 years (mean 15.1 months). The exent of tonsi llar herniation and other hindbrain anomalies was assessed on preopera tive magnetic resonance imaging. The infants with Chiari-II malformati ons underwent cervical laminectomies, whereas the other young children with Chiari-I malformations or achondroplasia underwent suboccipital craniectomy as well as cervical laminectomy. In Chiari malformation, t he dural band was divided; in achondroplasia, there was no identifiabl e dural band. Following bony decompression and division of the identif iable dural band, immediate expansion of the stenotic region with visi ble cerebrospinal fluid space posterior to the neural elements could b e ascertained by intraoperative ultrasonography. During a follow-up pe riod ranging from 4.5 months to 4 years (mean 22 months), all patients made improvements in their symptoms, 3 having complete resolution of their symptoms. This preliminary experience indicates that in children 2 years of age or younger, posterior fossa bony decompression without duraplasty can be effective treatment for Chiari malformations or ach ondroplasia.