Introduction: Chiari malformations (CM) are characterized by congenital hypoplasia of the posterior fossa and caudal displacement of cerebellar tissue below the foramen magnum. The two most prevalent types, CM Type 1 and Type II, are most commonly treated surgically with posterior fossa decompression. In this series, we present 75 patients over a 15-year period who underwent repeat Chiari decompression. To our knowledge, this is the first series to report outcomes following repeat posterior fossa decompression.

Methods: Eighty-three patients underwent repeat Chiari decompression by a single surgeon (HG) between 2001 and 2017. Thirteen patients were excluded due to lack of follow-up, leaving a study group of 70. Sixty-five patients had CM type I, and 5 had CM type II. Surgery was performed for recurrent or residual debilitating symptoms along with restriction of CSF flow, tethering, and/or crowding of the neural structures at the level of the foramen magnum on MRI. The length of follow-up ranged from 3-179 months. Outcomes were assessed using the Chicago Chiari Outcome Scale (CCOS).

Results: The patients' ages ranged from 2-67 years. Sixty-one patients had had 1 previous decompression, 6 had had 2, 2 had had 3, and 1 had had 4 (mean 1.2). Their CCOS scores ranged from 6-16. The mean CCOS score was 14.36/16, which correlates with a good outcome. Complications included pseudomeningocele (15, 21%), wound hematoma (2, 2.9%), and deep infection (1, 1.4%). Among the patients with pseudomeningocele, 7/15, or 10% of the group, were diagnosed with hydrocephalus and underwent shunt placement.

Conclusions: Patients with recurrent Chiari symptoms and stenosis may benefit from repeat decompression. Re-exploration was not associated with recurrent adhesions or obstruction. The risk of CSF leak appears higher in these patients, compared to 2-10% nationally for initial decompressions.

Patient Care: Surgical re-exploration will be considered in carefully-selected patients who become symptomatic from recurrent Chiari stenosis.

Learning Objectives: 1) Understand the benefits, risks and objectives of Chiari re-exploration/decompression surgery. 2) Become familiar with management of Chiari co-morbidities such as hydrocephalus and connective tissue disorder.

References: Gilmer HS, et al. Surgical Decompression for Chiari Malformation Type I: An Age-Based Outcome Study Based on the Chicago Chiari Outcome Scale. World Neurosurgery107:285-290, 2017. Aliaga L, et al. A novel scoring system for assessing Chiari malformation type I treatment outcomes. Neurosurgery 70(3):656-664, 2012. Arnautovic A, et al. Pediatric and adult Chiari malformation Type I surgical series 1965-2013: A review of demographics, operative treatment, and outcomes. Journal of Neurosurgery: Pediatrics 15(2):161-177, 2015.