Predictive value of posterior cranial fossa morphology in the decompression of Chiari malformation type I

Abstract

Posterior fossa decompression (PFD) is the standard procedure for the treatment of Chiari malformation type I (CMI). Although most patients have satisfactory surgical outcomes, some show no improvement or even a worsening of symptoms. Patient selection is thought to account for these different surgical outcomes. Our aim was to evaluate the predictive value of the preoperative posterior cranial fossa (PCF) morphology on the efficacy of PFD. Data from 39 CMI patients with CMI-related symptoms who underwent occipital foramen enlargement + C-1 laminectomy + enlarged duraplasty were retrospectively collected from January 2011 to May 2018. The patients were divided into improved and unimproved groups according to the modified Chicago Chiari Outcome Scale. Demographic information and clinical history, including preoperative comorbidities and clinical manifestations, were recorded for the 2 groups and compared. PCF morphology was assessed based on 13 linear, 8 angular, 4 areal parameters and 4 ratios related to these liner and areal parameters. The data were then analyzed statistically. Of the 39 patients with CMI, 24 showed improvement after PFD (61.5%), whereas the remaining 15 patients showed no improvement (38.5%). The preoperative symptoms lasted 1 to 240 months, with a median of 24 months. The follow-up period ranged from 2 to 82 months, with a median of 27 months. The improved and unimproved groups differed significantly with regard to upper limb numbness (OR = 10, P = .02) and upper limb weakness (OR = 4.86, P = .02). The 2 groups did not differ significantly with regard to any morphological parameters such as tonsillar descent, syrinx size. Preoperative upper limb numbness and upper limb weakness are unfavorable factors that influence the outcome of PFD in patients with CMI. However, the morphology of PCF cannot predict the response to PFD in patients with CMI.

Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines for Patients With Chiari Malformation: Symptoms

“…Of these, 44 were rejected for not meeting the inclusion criteria or for being off-topic. Thirty-five were selected 7-40 for this systematic review (Appendix III, https://www.cns.org/guidelines/browse-guidelines-detail/2-symptoms).…”

Use of Artificial Intelligence in the Prediction of Chiari Malformation Type 1 Recurrence After Posterior Fossa Decompressive Surgery

“…In their study, while symptom recurrence did not differ as a function of the degree of tonsillar ectopia, patients with both ventral and dorsal decrease in CSF flow after surgery had reduced recurrence rates and patients with just dorsal decrease flow had larger recurrence rates. Liu et al found that posterior cranial fossa morphology did not predict response to posterior fossa decompression in CM1 [ 18 ]. Some studies have found that syrinx size change and tonsillar tip distance from foramen magnum do not have a predictive association with outcome or recurrence, while others have found an association between syrinx size reduction and postoperative symptomatic improvement [ 19 ].…”

“…Some studies have found that syrinx size change and tonsillar tip distance from foramen magnum do not have a predictive association with outcome or recurrence, while others have found an association between syrinx size reduction and postoperative symptomatic improvement [19]. Studies looking at clinical features that predict CM1 recurrence have found that longer duration of headache, frontal headache, and vertigo independently increased the likelihood of symptom recurrence after decompression, and preoperative upper limb numbness and weakness are unfavorable factors predicting the outcome of posterior fossa decompressions in patients with CM1 [12,18]. Prognostic tools including the Chiari Severity Index and a points-based algorithm of Thakar et al have been developed to consolidate clinical and neuroimaging features that predict recurrence; however, Feghali et al's external validation study concluded that these scoring systems failed to provide prediction value of clinically meaningful improvement following decompression [4][5][6].…”

Foramen Magnum Decompression with Outer Dura Matter Layer Resection for Chiari Type I Malformation: Factors Correlated with Syrinx Reduction

“…Alperin et al [ 23 ] suggested that physiological measures can be stronger predictors than morphological measures of posterior cranial fossa after FMD for CMI. Liu et al [ 24 ] concluded that the morphology of the posterior cranial fossa cannot predict the response to FMD in patients with CMI. Our study revealed no significant changes in the bone morphometric parameters of the craniocervical junction, as well as the atlanto-occipital instability, such as the Wiesel-Rothman interval, basion-axial interval, and ADI.…”