OBJECT:
Surgery for Chiari malformation Type I (CM-I) is one of the most common neurosurgical procedures performed in children, although there is clearly no consensus among practitioners about which surgical method is preferred. The objective of this meta-analysis was to compare the outcome of posterior fossa decompression with duraplasty (PFDD) and posterior fossa decompression without duraplasty (PFD) for the treatment of CM-I in children.
METHODS:
The authors searched Medline-Ovid, The Cochrane Library, and the conference proceedings of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons (2000-2007) for studies meeting the following inclusion criteria: 1) surgical treatment of CM-I; 2) surgical techniques of PFD and PFDD being reported in a single cohort; and 3) patient age < 18 years.
RESULTS:
Five retrospective and 2 prospective cohort studies involving a total of 582 patients met the criteria for inclusion in the meta-analysis. Of the 582 patients, 316 were treated with PFDD and 266 were treated with PFD alone. Patient age ranged from 6 months to 18 years. Patients undergoing PFDD had a significantly lower reoperation rate (2.1 vs 12.6%, risk ratio [RR] 0.23, 95% confidence interval [CI] 0.08-0.69) and a higher rate of cerebrospinal fluid-related complications (18.5 vs 1.8%, RR 7.64, 95% CI 2.53-23.09) than those undergoing PFD. No significant differences in either clinical improvement (78.6 vs 64.6%, RR 1.23, 95% CI 0.95-1.59) or syringomyelia decrease (87.0 vs 56.3%, RR 1.43, 95% CI 0.91-2.25) were noted between PFDD and PFD.
CONCLUSIONS:
Posterior fossa decompression with duraplasty is associated with a lower risk of reoperation than PFD but a greater risk for cerebrospinal fluid-related complications. There was no significant difference between the 2 operative techniques with respect to clinical improvement or decrease in syringomyelia.
So, the last sentence(above) indicates no statistically significant difference, so we shouldn't open the dura, right?
In my opinion, that is wrong. We simply don't have enough patients to meet statistical significance. So look at the trends.
Syringomyelia improved in 87% of patients with duraplasty and in 56.3% without. That means the failure rate was 13% with duraplasty and 43.7%(more than 3x higher!!) without duraplasty. Clinical improvement was noted in 78.6% with duraplasty and 64.6% without(again failure rates of 21.4% vs 35.4%).
To me, that data means your risk of surgical failure is at least twice as high without duraplasty. But, it also means many patients are getting a duraplasty that don't need it(they could improve without the duraplasty).
So, now you have a discussion with the patient. Do you want to have a more invasive procedure(duraplasty), which is more likely to be a one time operation, or a less invasive procedure(bone only) that has a higher failure rate?
Hopefully, we will find a way to distinguish patients who will fall into each category but we aren't there yet. At the meetings I attend, the vast majority of MDs perform a duraplasty.
In my practice, for those who fail to improve, this is the setting in which I use a cine MRI. If there is obstruction to CSF flow, your decompression was inadequate(again, we know you are more likely to improve with duraplasty when you have documented CSF flow obstruction at the craniovertebral junction). If you have normal flow, your success rate for a repeat operation will be <50%.
Hope these thoughts were helpful.