Posterior Fossa Decompression without Duraplasty in Infants and Young Children for Treatment of Chiari Malformation and Achondroplasia

Abstract

Some children with Chiari malformation and achondroplasia require posterior fossa decompression that typically includes expansion of the dural tube with duraplasty. Infants and young children, however, may have a more distensible dura mater than do older patients. Furthermore, the structures that compress the hindbrain of young patients may be the bone and abnormally thickened atlantooccipital membrane, i.e., dural band, rather than the dura mater. We have treated 7 children who had Chiari malformation or achondroplasia with posterior fossa decompression without duraplasty. All children were symptomatic; 3 had Chiari-I malformations, 2 Chiari-II malformations, and 2 achondroplasia. The age range was 3 months to 2.5 years (mean 15.1 months). The exent of tonsillar herniation and other hindbrain anomalies was assessed on preoperative magnetic resonance imaging. The infants with Chiari-II malformations 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, the dural band was divided; in achondroplasia, there was no identifiable dural band. Following bony decompression and division of the identifiable dural band, immediate expansion of the stenotic region with visible cerebrospinal fluid space posterior to the neural elements could be ascertained by intraoperative ultrasonography. During a follow-up period 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 achondroplasia.

Acute Hydrocephalus following a Chiari I Decompression

“…While most authors agree on the need to perform a bony decompression of the posterior fossa, debate exists regarding whether or not the dura should be opened and a duraplasty performed [2, 4, 6, 7, 8, 9, 10, 11, 12]. Our patients with Chiari I malformations undergo posterior fossa decompression, opening of the dura in a linear manner, exploration of the fourth ventricular outlet and patch grafting, usually with local tissue such as periosteum.…”

Treatment of Chiari type I malformation in patients with and without syringomyelia: a consecutive series of 66 cases

“…58 Others, like us, prefer small craniectomies; the recently described cerebellar ptosis that occurrs after larger craniectomy 33 may support this more conservative approach. Some authors have advocated that the craniectomy alone may be sufficient, 50,77 whereas others have argued that the dura must be opened. Some have attempted opening of the dura only, but not the arachnoid.…”

Reformation of the Posterior Atlanto-Occipital Membrane following Posterior Fossa Decompression with Subsequent Constriction at the Craniocervical Junction

“…1) is encountered with a routine suboccipital craniectomy such as in posterior cranial fossa decompression for tonsillar ectopia (Chiari I decompression) and is often found to be thickened (dural band) in this pathological condition [1, 2]. This membrane is often left in place with its connection to the anterior periosteum of the posterior arch of the atlas and after removal of the posterior arch, the membrane is usually incised with the underlying outer and inner leaves of the dura mater as one layer [2].…”

“…This membrane is often left in place with its connection to the anterior periosteum of the posterior arch of the atlas and after removal of the posterior arch, the membrane is usually incised with the underlying outer and inner leaves of the dura mater as one layer [2]. Some advocate merely transecting this membrane and or incising the outer layer of the dura mater for adequate decompression of the posterior fossa without duraplasty for symptomatic hindbrain herniation [1, 3]. We report a case of a pediatric patient who, at a second operation for a symptomatic hindbrain hernia, was found to have a reconstituted PAO that significantly indented the craniocervical junction.…”