Posterior fossa decompression for children with Chiari I malformation and hydrocephalus

INTRODUCTION Chiari I malformation (CMI) and hydrocephalus often coexist, with no clear understanding of the cause-and-effect relationship. In the absence of other associated etiologies, the traditional teaching has been to treat the hydrocephalus first, partly to minimize the risk of cerebrospinal fluid (CSF) leak from CMI decompression in the setting of elevated ICP. We describe a series of consecutive pediatric patients with CMI and hydrocephalus, the majority of whom were managed with posterior fossa decompression. METHODS A retrospective review was conducted on consecutive children who presented to the senior author with both hydrocephalus and CMI, with emphasis on rationale for and outcomes of surgical intervention, including the need for additional surgery. RESULTS There were 14 patients aged 2 weeks to 16 years (median 2 years) who presented with Chiari I and hydrocephalus. Four of these underwent posterior fossa decompression without duraplasty (PFD) as first-line therapy (one of whom eventually required duraplasty), 7 had PFD with duraplasty (PFDD), 1 received a ventriculoperitoneal shunt (VPS), and two had endoscopic third ventriculostomy (ETV). Of the 11 who had PFD/D, 9 (90%) had significant symptom improvement/resolution, 7 (55%) showed decrease in ventricle size, and 1 (10%) required VPS placement for persistent hydrocephalus. Both ETV patients improved clinically, and 1 showed decrease in ventricle size. There were no pseudomeningoceles, infections, or neurological deficits. One CSF leak occurred after an ETV and was successfully treated with wound revision. CONCLUSION In patients with both CMI and hydrocephalus, treating the CMI first in an effort to avoid a shunt can be safe and effective. In this series, PFDD in the setting of hydrocephalus did not result in CSF leak or pseudomeningocele. While limited by a small sample size, these data support a causative relationship between CMI and hydrocephalus.