Introduction: Controversy continues surrounding the optimal surgical approach to Chiari decompression and whether the dura needs to be opened. Assessment of long-term outcomes looking specifically at failure rates, and associated factors, for bone-only decompression versus duraplasty was undertaken.
Methods: Retrospective review of patients undergoing decompression from 1996 -2014(18yrs) at CNMC identified patients requiring additional Chiari decompression for worsening symptoms or persistent syringomyelia(IRB #Pro268). Preoperative symptoms, imaging studies, operative reports and post-operative follow up were available for all included patients.
Results: 19/195(9.74%) patients were identified requiring additional Chiari decompression. Average age at initial surgery was 9.4 years(1-17) and 10.3 years(3-20) for second surgery. Length of time between surgeries was 2.8 years(4m to 8 years) with follow-up 47m(1-224). Patients undergoing bone-only decompression demonstrated 10/70(14%) need for additional Chiari surgery whereas 9/125(7%) of patients having duraplasty required second operation(OR:2.14,CI:0.82-5.571,p=0.11). The syrinx cohort demonstrated a similar failure rate(OR:2.04,CI:0.577-7.21,p=0.26). Analysis of holocord syrinxes was also not significant(OR:2,CI:0.43-9.2,p=0.36).Factors contributing to reoperation for both surgical cohorts found inadequate bony decompression in 2/19, bone regrowth 3/19 and arachnoid scarring at 4th ventricular outflow in 17/19 patients. 10/19(53%) required placement of 4th ventricular stent. 6/19(32%) had craniofacial co-morbidity. Complications were seen in 2/70(3%) for bone-only decompression vs 26% (CSF leak/14;pseudomeningocele/26;meningitis/4,p<0.001).
Conclusions: Comparison of Chiari failures does not appear to differentiate between open and closed decompression. The most common cause of failure was the presence of arachnoid scaring at the 4th ventricular outflow in both surgical cohorts. Craniofacial co-morbidity increased the likelihood of surgical failure, especially when hydrodynamic issues were involved.
Patient Care: This data demonstrates that there is no significant differnce in failure rates between bone only decompressions and failure rates even in patients with syrinxes. There is however, a signficantly higher morbidity rate when duraplasty is performed. The most common cause of failure seen in the second surgery was due to arachnoid bands obstructing fourth ventricular outflow. If the dura is to be opened,care should be taken to explore the this area and place a stent if necessary.
Learning Objectives: To determine if there is a difference in failure rates between a bone only posterior fossa decompression compared to a duraplasty in treatment of Chiari 1 malformations and if there are any preoperative characteristics that would place patients at higher risk for failure