An efficacy analysis of posterior fossa decompression techniques in the treatment of Chiari malformation with associated syringomyelia

doi:10.1016/j.jocn.2011.01.026

Journal of Clinical Neuroscience

Volume 18, Issue 10, October 2011, Pages 1346-1349

https://doi.org/10.1016/j.jocn.2011.01.026 Get rights and content

Abstract

A retrospective study of the efficacy of posterior fossa decompression (PFD) was carried out in 132 patients with Chiari malformation (CM) with associated syringomyelia (SM). Of these 132 patients, 69 received extended PFD (large craniotomy group), and the other 63 patients received only local PFD (small craniotomy group). At the short-term postoperative evaluation (1–4 weeks) the extended PFD appeared to be more effective than the local PFD (p < 0.05). However, there was no significant difference in long-term analysis (6 months–11 years) (p > 0.05). In the large craniotomy group, there was no difference between the short-term and long-term efficacy (p > 0.05). However, in the small craniotomy group, long-term efficacy clearly improved (p < 0.05). Furthermore, patients who had undergone local PFD exhibited more obvious radiological improvement of SM (p < 0.05) and fewer postoperative complications compared to patients undergoing extended PFD (p < 0.05). Therefore, local PFD is preferable for the surgical treatment of CM with associated SM.

Introduction

Chiari malformation (CM) is a congenital disease that manifests as a narrow posterior cranial fossa and an obstruction of the foramen magnum. Approximately 50% to 70% of patients with CM present with associated syringomyelia (SM).[1], [2] CM with associated SM is a common congenital neurosurgical disease,³ which often presents in patients aged 20 years to 50 years and is slightly more prevalent in females than in males.

To date, no hypothesis has provided an entirely satisfactory explanation for the pathogenesis of CM with SM.⁴ The most widely accepted view is that a narrow posterior fossa and obstruction of the foramen magnum lead to this disease.[5], [6], [7], [8] Thus, the primary goal of treatment is the expansion of the posterior fossa volume to release the compression of the brain stem and spinal cord. This approach seeks to restore the normal cerebrospinal fluid (CSF) circulation, and to balance the pressure difference between the brain and the spine to prevent further neurological damage and to promote recovery.

Currently, the elements of the operative approaches for the treatment of CM with associated SM include the following: posterior fossa decompression (PFD);⁹ posterior fossa dural dilation duraplasty;¹⁰ resection of displaced cerebellar tonsils and dural suture;¹¹ and resection of displaced cerebellar tonsils to free the original width of the central canal and dural suture. Although the surgical details of the above-described approaches differ, a crucial element in all approaches is determining the extent of decompression. However, there is no universal standard for determining the appropriate extent of PFD. Further, there is disagreement regarding the relative efficacy of extended decompression of the squama occipitalis and local decompression.[10], [12]

In this retrospective study, we recruited 132 patients with Chiari I malformation and SM who received surgical treatment at Daping Hospital (Third Affiliated Hospital of Third Military Medical University) from June 1997 to June 2008. The short-term and long-term efficacies of the two modes of PFD were evaluated.

Section snippets

Patient demographics and clinical signs

Of the 132 patients, 58 were male and 74 were female (male:female, 1:1.3); their ages ranged from 14 years to 62 years (average ± standard deviation [SD], 33 ± 13 years). The duration of disease ranged from 10 months to 12 years (average ± SD, 2.3 ± 1.2 years). The PFD with extended craniotomy plus dural repair (decompression size: 5 cm × 6 cm) was routinely performed in 69 patients from June 1997 to August 2002 (large craniotomy group), and PFD with local craniotomy plus dural repair (decompression size: 3 cm × 4

Results

According to Tator outcome scoring,¹³ patients with improved symptoms and physical signs were graded “excellent”; those with stable symptoms and signs were graded “good”; and those with worsening symptoms and signs were graded “poor.” Patients with excellent and good outcomes were classified as receiving effective treatment. All patients were available at follow-up. The follow-up time ranged from 6 months to 11 years (mean, 2.3 years).

Discussion

Posterior fossa reconstruction for the treatment of CM is the only surgical technique that achieves foramen magnum decompression,¹⁴ reconstruction of normal CSF circulation channels, and restoration of normal CSF circulation. PFD with dural reconstruction can expand the posterior fossa volume, thereby restoring normal cranial–spinal CSF circulation.¹⁵ For this reason, PFD has historically been the primary surgical technique for treating SM.¹⁶

The CSF circulation can be damaged by obstruction of

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Cited by (24)

Three-Dimensional Volumetric Magnetic Resonance Imaging Analysis of Syringomyelia Evolution After Posterior Fossa Decompression for Chiari Malformation Type1
2023, World Neurosurgery
This study aims to introduce a method of three-dimensional (3D) volume magnetic resonance imaging (MRI) measurements to evaluate the evolution of syringomyelia (SM) in adults with Chiari malformation type 1 (CM-1) after posterior fossa decompression (PFD), to provide reproducible and accurate measurements.
Radiologic and clinical data were obtained for 28 patients. MRI 3D syrinx volumes were evaluated by 2 observers using Philips Healthcare Tumor Tracking tool.
The mean SM preoperative volume was 9.1 ± 15.3 cm³ versus 4.6 ± 8.7 cm³ postoperatively, corresponding to a volume variation reduced by –50% ± 33.4%. A total of 21 patients (75%) showed >25% reduction in SM volume postoperatively and 25 patients (89.2%) showed good to excellent postoperative clinical outcomes. Very high interobserver and intraobserver agreement was noted for 3D volumetric analysis with Cohen weighted κ coefficients (0.899–0.991). A negative correlation was found between the number of involved metameres and the postoperative SM volume reduction (Pearson correlation coefficient = 0.378; P = 0.047). Patients with better clinical outcomes had fewer syrinx septae (F = 8.830; P = 0.001). Similarly, better syrinx volume reduction was associated with fewer septae (F = 1.554; P = 0.233). A positive relationship was observed between clinical outcomes and postoperative syrinx volume reduction (F = 1.554; P= 0.233), with data similar to the reported literature.
This study shows that 3D volume measurement of the syrinx cavity on MRI is a reproducible and accurate method to assess the postoperative evolution of SM in CM-1 after PFD. Most patients (75%) showed a reduction of SM volume, with a mean volume decrease of 50%. The reliability is yet to be validated in further larger studies.
Individualized surgical treatment of Chiari 1 malformation: A single-center experience
2023, Clinical Neurology and Neurosurgery
To present our experience with an individualized surgical approach to treat Chiari malformation type 1.
Based on (1) neurological symptoms, (2) the existence and extent of a syrinx and (3) the degree of the tonsillar descent we performed four types of approaches on a case-by-case basis in 81 patients: (1) foramen magnum decompression (FMD) with dura splitting (FMDds); (2) FMD with duraplasty (FMDdp); (3) FMD with duraplasty and tonsillar manipulation (FMDao); and (4) tonsillar resection/reduction (TR). Patient characteristics, Chiari Severity Index (CSI), fourth ventricular roof angle (FVRA) and Chicago Chiari Outcome Scale (CCOS) were analyzed.
CCOS was between 13 and 16 points in 8/11 (73 %) patients after FMDds, 38/45 (84 %) patients after FMDdp, and 24/24 (100 %, one patient lost to follow-up) patients after TR. We experienced an overall complication rate of 13.6 % (11/81) in this series, whereas seven of these eleven complications (64 %) occurred in the FMDao group and the complication rate increased with the invasiveness of the approach (0 % FMDds; 4 % FMDdp; 12 % TR).
Given the clear correlation between the extend of the approach and the complication rate the least invasive approach necessary to achieve clinical improvement should be selected. Due to the high complication rates, FMDao should not be used as a treatment option. The severity of the tonsillar descent, basilar invagination and current CM1 scores could be used to aid in the approach selection.
Low versus High Intracranial Compliance in Adult Patients with Chiari Malformation Type 1–Comparison of Long-Term Outcome After Tailored Treatment
2023, World Neurosurgery
In patients with Chiari malformation type 1 (CMI) presenting with low intracranial compliance (ICC), foramen magnum decompression (FMD) often fails and the complication rate may be higher. We therefore routinely perform a preoperative assessment of ICC from intracranial pressure measurement. Patients with low ICC are treated with ventriculoperitoneal shunt (VPS) before FMD. In this study, we assess the outcome of patients with low ICC, compared with patients with high ICC treated with FMD alone.
We reviewed the clinical and radiologic data of all consecutive patients with CMI treated between April 2008 and June 2021. ICC was assessed by overnight measurement of the pulsatile intracranial pressure: mean wave amplitude (MWA) above a previously defined threshold for abnormality was considered a surrogate marker for low ICC. The outcome was scored by Chicago Chiari Outcome Scale.
Of 73 patients, 23 with low ICC (average MWA 6.8 ± 1.2 mm Hg) received VPS before FMD, whereas 50 with high ICC (average MWA 4.4 ± 1.0 mm Hg) received only FMD. After a mean follow-up of 78.7 ± 41.4 months, 96% of all patients subjectively improved. The mean Chicago Chiari Outcome Scale score was 13.1 ± 2.2. Enlargement of cerebrospinal fluid space in the foramen magnum was achieved in 95% and regression of syringomyelia in 74% of cases. We found no significant difference in outcome between the patients with low and high ICC.
By identifying patients with CMI associated with low ICC and tailoring their treatment by VPS before FMD, we achieved favorable clinical and radiologic outcomes comparable to those with high ICC.
The 270° Circumferential Microsurgical Decompression of the Foramen Magnum in Adult Chiari Malformation Type I: Single Surgeon Series of 130 Patients with Syringomyelia, Neurologic, and Headache Outcomes
2021, World Neurosurgery
Citation Excerpt :
In addition, our study has a longer follow-up (approximately 6 months longer than the mean of other studies; Table 3) and is the only prospective study. Our study period was almost 2 times longer than the average length of other adult studies (15 vs. 8 years).1-33,37-72 The goal of our study was to precisely measure, radiologically and clinically, the surgical outcomes regarding resolution/improvement of syringomyelia, neurologic status, and preoperative headaches and to compare those outcomes with our reported systematic review of surgical outcomes of studies of CM-I in adults reported in 1963–2013 and included additional studies from 2014–2019.1
Chiari malformation type I (CM-I) is a craniocervical junction disorder associated with descent of the cerebellar tonsils >5 mm. The prevalence of CM-I is common, including 0.5%–3.5% in the general population, 0.56%–0.77% on magnetic resonance imaging, and 0.62% in anatomic dissection studies. We sought to measure our surgical outcomes related to resolution/improvement of headaches, neurologic outcomes, and syringomyelia compared with reported adult CM-I studies from 2000–2019.
From December 2003 to June 2018, the first author (K.I.A.) performed 270° circumferential decompression on adult (>18 years) patients with CM-I. At admission and follow-up, all parameters were numerically evaluated; headaches were self-reported on the visual analog scale, neurologic condition was evaluated using Karnofsky Performance Status and European Myelopathy Score, and syrinx width (if present) was measured on magnetic resonance imaging by grades I–IV. All parameters were analyzed, compared, and statistically tested. We compared results with our previously reported and updated systematic review of operative adult CM-I studies (studies from 2000 to 2019).
In our series, 118/121 (98%) experienced headache improvements and 100% experienced neurologic improvements. Complete syrinx resolution was experienced by 35/43 (81%); 8 (19%) showed significant improvement. In data from reported studies (2000–2019), only 79% experienced headache resolution, 77% improvement of neurologic status, and 74% resolution/improvement of syrinx (mean).
Our modified 270° circumferential microsurgical foramen magnum decompression for adult CM-I appears to be beneficial in improvement of outcomes, namely in resolution of the syrinx, neurologic symptoms, and headaches. We also confirm the association of body mass index with CM-I. Further studies are needed to confirm our results.
No significant difference between chiari malformation type 1.5 and type I
2017, Clinical Neurology and Neurosurgery
Chiari malformation Type 1.5 (CM 1.5) was defined as the association of Chiari malformation Type I (CM I) and brainstem herniation. The objective was to demonstrate the difference of clinical features and surgical outcomes between CM 1.5 and CM I.
All CM 1.5 and CM I adult patients who underwent posterior fossa decompression with duraplasty at our institution between 2006 and 2010 were retrospectively reviewed. Clinical characteristics, imaging features, and long-term outcomes were compared between CM 1.5 and CM I patients.
A total of 142 adult patients were enrolled, including 27 CM 1.5 and 115 CM I patients. The average follow-up period was 102 months. Age at diagnosis was significantly younger in CM 1.5 group than CM I group (p = 0.039). And the degree of tonsillar herniation was significantly more severe in CM 1.5 group than CM I group (p < 0.001). There was no significant difference in other clinical and imaging characteristics. Moreover, improvement of symptoms was observed in 21 CM 1.5 patients (77.8%) and 94 CM I patients (81.7%), and no significant difference was detected (p = 0.637). There was no significant difference in the resolution of syringomyelia between CM 1.5 (72.7%) and CM I (76.5%) patients, either (p = 0. 710).
Although CM 1.5 patients presented with brainstem herniation and more severe tonsillar herniation, other clinical and imaging features and surgical outcomes were similar with CM I patients. We think CM 1.5 is just a subtype of CM I, rather than a unique type of Chiari malformations.
Surgical outcomes after posterior fossa decompression with and without duraplasty in Chiari malformation-I
2014, Clinical Neurology and Neurosurgery
Citation Excerpt :
The technique for decompression, however, varies based on the varied understanding of pathophysiology, surgeons’ preference and patient characteristics [10,16–23]. Several techniques that have been advocated for PFD includes bone decompression only; extradural lysis of sclerotic tissue and removal of the outer dural layer [17,24–26]; intradural extra-arachnoid durotomy with and without duraplasty; intra-arachnoid lysis of the scarring and adhesions around the herniated tonsil [10,12,27–31]; reduction of the herniated tonsil by coagulation or partial tonsillectomy [11,21,31]; as well as opening the foramen of magendie and obex plugging [9,32,33]. The intradural techniques are associated with increased risk of complications including wound infection, CSF leak, pseudomeningocele, meningitis and complication associated with dural graft [5,13,16,29,34–39].
Chiari malformation-I (CM) is one of the most controversial entities in the contemporary neurosurgical literature. Posterior fossa decompression (PFD) is the preferred treatment for CM with and without syringomyelia. A variety of surgical techniques for PFD have been advocated in the literature. The aim of this study was to evaluate our results of surgically treated patients for CM-I with and without syringomyelia; using extradural dura-splitting and intradural intraarachnoid techniques.
A retrospective review of the medical records of all the patients undergoing PFD was conducted. Symptomatic patients with tonsillar herniation ≥ 3-mm below the foramen magnum on neuroimaging, and CSF flow void study demonstrating restricted or no CSF flow at the craniocervical junction, were offered surgical treatment. In patients without syringomyelia, extradural decompression with thinning of the sclerotic tissue at the cervicomedullary junction and splitting of outer dural layer was performed. In patients with syringomyelia, the dura was opened and an expansile duraplasty was performed.
The mean age of 8 males and 34 females was 33.8 years (range, 16–58 years). Headache (39/41; 95%), and/or tingling and numbness (17/41; 42%) were the most common presenting symptoms. The syrinx was associated with CM-I in 5/41 (12%) patients. PFD without durotomy was performed in 29/41 (73%) patients. The mean duration of preoperative symptoms was significantly longer in duraplasty group (4.6 versus 1.7 years, P = 0.005, OR = 0.48, CI = 0.29–0.8). The use of duraplasty was significantly associated with presence of complications (P = 0.004, OR = 0.5, CI = 0.3–0.8) and longer duration of hospital stay (P = 0.03, OR = 2.7, CI = 1.1–6.8). The overall complication rate was 6/41(15%) patients. The overall improvement rate was evident in 84% (36/41); 12% (5/41) were stable; and 5% (2/41) had worsening of symptoms. The history of prior CM decompression was associated with unfavorable outcomes (P = 0.04, OR = 14, CI = 1.06–184). One patient experienced recurrence one year after the PFD with duraplasty.
The present study reports favorable surgical outcomes with extra-dural decompression of the posterior fossa in patients CM-I without syringomyelia. For patients with syringomyelia and history of prior PFD, intradural intra-arachnoid decompression is required. The prior history of decompression was associated with unfavorable outcomes. The use of duraplasty was associated with longer duration of hospital stay and higher complication rate. Further large cohort prospective study is needed to provide any recommendation on the indication of intra or extradural decompression for a given CM-I patient.

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^†: These authors contributed equally to this work.

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Clinical StudyAn efficacy analysis of posterior fossa decompression techniques in the treatment of Chiari malformation with associated syringomyelia

Abstract

Introduction

Section snippets

Patient demographics and clinical signs

Results

Discussion

J Neurol Sci

J Clin Neurosci

Clin Neurol Neurosurg

J Clin Neurosci

Neurosurg Clin N Am

Chiari I malformation with syringomyelia: evaluation of surgical therapy by magnetic resonance imaging

J Neurosurg

Surgical treatment of “hindbrain related” syringomyelia: long-term results

Acta Neurochir

Magnetic resonance imaging in the management of primary and secondary syringomyelic cavities and of other cystic lesions of the spinal cord

Acta Neurochir

Malformations of the craniocervical junction (Chiari type I and syringomyelia: classification, diagnosis and treatment)

BMC Musculoskelet Disord

On the pathogenesis of syringomyelia: a review

J R Soc Med

A unifying hypothesis for hydrocephalus, Chiari malformation, syringomyelia, anencephaly and spina bifida

Cerebrospinal Fluid Res

Clinical Study
An efficacy analysis of posterior fossa decompression techniques in the treatment of Chiari malformation with associated syringomyelia