Here's some of the abstracts I quote patients.
Effects of posterior fossa decompression with and without duraplasty on Chiari malformation-associated hydromyelia.
Munshi I, Frim D, Stine-Reyes R, Weir BK, Hekmatpanah J, Brown F.
Section of Neurosurgery, University of Chicago, Illinois 60637, USA.
OBJECTIVE: The optimal surgical treatment of Chiari malformation is unclear, especially in patients with hydromyelia. Various surgical approaches have included suboccipital craniectomy, syringostomy, obex plugging, syringosubarachnoid shunting, and fourth ventriculosubarachnoid shunting. The purpose of this study is to differentiate extradural and intradural approaches in the treatment of Chiari I malformation. METHODS: We reviewed the medical records and magnetic resonance imaging (MRI) scans of 34 surgical corrections' of Chiari malformation performed at our institution from 1988 to 1998. The age and sex of the patient, the presence of hydromyelia, the type of surgery (duraplasty or nonduraplasty), and the clinical outcome were determined. RESULTS: Eleven patients underwent posterior fossa decompression (PFD) and C1 laminectomy without duraplasty. Eight (73%) of these patients had an improvement in symptoms. Seven of the 11 patients had hydromyelia. Of the six patients who underwent follow-up MRI, three (50%) had a decrease in the size of the hydromyelia, and all three had clinical improvement. We also noted a morphometric increase in posterior fossa volume on postoperative MRI scans in these three patients, which was not observed in those without improvement. Two of the three patients whose hydromyelia did not decrease on follow-up MRI scans worsened clinically, and one underwent a reoperation with duraplasty. Twenty-three patients underwent combined PFD, C1 laminectomy, and duraplasty. Twenty (87%) of these patients had improvement. Twelve of the patients who underwent duraplasty had hydromyelia; nine underwent follow-up MRI. All nine of these patients (100%) had a decrease in the cavity size, including eight with clinical improvement. There were 10 minor complications (seroma, 4; superficial infection, 3; cerebrospinal fluid leak, 2; aseptic meningitis and occipital nerve pain, 1) when the dura was opened, compared with one superficial wound infection that resolved in patients who underwent PFD only. CONCLUSION: PFD, C1 laminectomy, and duraplasty for the treatment of Chiari I malformation may lead to a more reliable reduction in the volume of concomitant hydromyelia, compared with PFD and C1 laminectomy alone. However, there seems to be a subset of patients whose symptoms will resolve and whose hydromyelic cavity will decrease with the removal of bone only. These patients seem to undergo a volumetric increase in the posterior fossa. Further studies are needed to better characterize these patients, to determine which patients with Chiari I malformation are better served with bony decompression only, and which will require duraplasty to resolve their hydromyelia.
PMID: 10834643 [PubMed - indexed for MEDLINE]
Surgical management of Chiari malformation: analysis of 128 cases.
Guo F, Wang M, Long J, Wang H, Sun H, Yang B, Song L.
Department of Neurosurgery, First Affiliated Hospital of Zhengzhou University, Zhengzhou, PR China.
OBJECTIVE: A variety of surgical interventions have been recommended for patients with Chiari malformations (CMs). In this study, we have evaluated the intraoperative findings and clinical outcome in different-aged patients with CMs undergoing posterior fossa decompression. METHODS: Sixteen pediatric and 112 adult cases with CMs underwent suboccipital craniectomy and wide duraplasty as well as autogenous bone grafting in selected cases. The clinical outcome was assessed by evaluation of postoperative signs and symptoms and magnetic resonance imaging of the craniocervical junction. RESULTS: The most striking intraoperative finding was the presence of a very thin membrane over the opening of the central canal; the occurrence of this membrane in pediatric patients was significantly higher than that in adults (94 and 43%, respectively; p < 0.05, Fisher's exact probability test). During the immediate postoperative period, 81% of pediatric CMs and 90% of adult CMs showed improved symptomatology and magnetic resonance imaging revealed favorable findings comprising syrinx collapse or reduction of the syrinx diameter in 14 (88%) pediatric and 92 (82%) adult CMs. During discharge from hospital, 103 (90%) patients with CMs type I and 11 (85%) with CMs type II achieved good results. However, there was a statistically significant difference in the occurrence of poor results between patients treated with bony fusion and those without fusion (24 vs. 6%;p < 0.05, Fisher's exact probability test). The incidence of vertebral instability was markedly augmented in pediatric CMs in comparison to adult CMs (19 vs. 2%; p < 0.01, Fisher's exact probability test). CONCLUSIONS: Suboccipital decompression and duraplasty with autogenous bone grafts in selected cases are effective treatments for most patients with CMs. A higher incidence of a special membrane over the obex and atlantoaxial instability were closely associated with childhood CMs. (c) 2007 S. Karger AG, Basel.
Hindbrain decompression for Chiari-syringomyelia complex: an outcome analysis comparing surgical techniques.
Hayhurst C, Richards O, Zaki H, Findlay G, Pigott TJ.
Department of Neurosurgery, Walton Centre for Neurology and Neurosurgery, Liverpool, UK.
The natural history of Chiari malformation and our ability to alter it is poorly understood, and reported results of hindbrain decompression show high recurrence rates. We report 11 years of experience of hindbrain decompression, to evaluate long-term outcome related to surgical technique. The results of patients who underwent hindbrain decompression between 1994 and 2005 were retrospectively analysed. We identified 96 patients from operative records and reviewed all clinical records for presenting symptomatology and examination findings. Decompression technique includes traditional decompression, duraplasty and bone--only decompression. Symptoms at the last available follow-up visit were defined by the assessing clinician as resolved, improved, unchanged or worse. There were 35 males and 61 females with a mean age of 33 years (range 6 - 62 years). The mean length of follow-up is 3.6 years with a range of 6 months to 9 years. Postoperative resolution or improvement in symptoms was seen in 75 patients (78%). Drop attacks and headaches were the most likely to respond to hindbrain decompression, showing improvement or resolution in 100 and 92% of cases. Dysaesthetic arm pain and weakness carried the worse prognosis with only 20% having symptom resolution. Sixteen patients had only bony decompression leaving the dura intact. In eight patients (66%) the headaches resolved following bony decompression alone. However the headaches were unchanged in 25% of cases. Dysaesthetic pain and weakness was unchanged in 60%. Restoration of CSF flow dynamics at the foramen magnum by surgical decompression does not consistently result in resolution of symptoms in all patients. Identification of predictors of successful outcome following decompression, coupled with early intervention and appropriate choice of procedure may result in improved outcomes. Although this is a retrospective study it suggests that bone only decompression should be reserved for patients with isolated headache.
Comparison of posterior fossa decompression with and without duraplasty for the surgical treatment of Chiari malformation Type I in pediatric patients: a meta-analysis.
Durham SR, Fjeld-Olenec K.
Department of Surgery (Pediatric Neurosurgery), Dartmouth Medical School, Hanover, NH, USA. ■■■■■■■■■■■■■■■■■
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.
I use those to explain to patients issues. In order to achieve statistical significance in the medical literature, the probablity that the results are due to random occurrences must be <5%(usually signified with p<0.05).
So there are many papers that don't prove statistical significance between opening the dura and not opening the dura and many MDs will use that as a reason not to open the dura. However, there are papers that confirm stastically improved reduction in syrinx with duraplasty(and none that confirm better outcomes with bony opening only, without duraplasty).
Let's look at the last abstract quoted. It states "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.". That means, there was no statistically signficant difference between opening the dura(PFDD) and not opening the dura(PFD). So we shouldn't be opening the dura, correct?
In my opinion, this is use of statistics to make your point. Because the patient volumes weren't large enough to reach statistical significance, doesn't mean you can't get useful data. In that paper, they state, 87% of syrinxes reduced in size when the dura was opened. 56.3% reduced in size when the dura wasn't opened. Reversed, 13% of syrinxes failed to improve when the dura was opened but 43.3% failed to improve if the dura wasn't opened. Your risk of failure without opening the dura is >300%(3x) higher!
When data is not statistically significant, one looks at trends. The trend here is very clear.
As everyone above stated, read, look at data, and make your own decision.
In my opinion, if the goal of the Chiari decompression is reduction is syrinx size, the literature is very clear. The dura should be opened. But I can't state that with proven statistical signficance.