OBJECTIVEAlthough various predictors of postoperative outcome have been previously identified in patients with Chiari malformation Type I (CMI) with syringomyelia, there is no known algorithm for predicting a multifactorial outcome measure in this widely studied disorder. Using one of the largest preoperative variable arrays used so far in CMI research, the authors attempted to generate a formula for predicting postoperative outcome.METHODSData from the clinical records of 82 symptomatic adult patients with CMI and altered hindbrain CSF flow who were managed with foramen magnum decompression, C-1 laminectomy, and duraplasty over an 8-year period were collected and analyzed. Various preoperative clinical and radiological variables in the 57 patients who formed the study cohort were assessed in a bivariate analysis to determine their ability to predict clinical outcome (as measured on the Chicago Chiari Outcome Scale [CCOS]) and the resolution of syrinx at the last follow-up. The variables that were significant in the bivariate analysis were further analyzed in a multiple linear regression analysis. Different regression models were tested, and the model with the best prediction of CCOS was identified and internally validated in a subcohort of 25 patients.RESULTSThere was no correlation between CCOS score and syrinx resolution (p = 0.24) at a mean ± SD follow-up of 40.29 ± 10.36 months. Multiple linear regression analysis revealed that the presence of gait instability, obex position, and the M-line–fourth ventricle vertex (FVV) distance correlated with CCOS score, while the presence of motor deficits was associated with poor syrinx resolution (p ≤ 0.05). The algorithm generated from the regression model demonstrated good diagnostic accuracy (area under curve 0.81), with a score of more than 128 points demonstrating 100% specificity for clinical improvement (CCOS score of 11 or greater). The model had excellent reliability (κ = 0.85) and was validated with fair accuracy in the validation cohort (area under the curve 0.75).CONCLUSIONSThe presence of gait imbalance and motor deficits independently predict worse clinical and radiological outcomes, respectively, after decompressive surgery for CMI with altered hindbrain CSF flow. Caudal displacement of the obex and a shorter M-line–FVV distance correlated with good CCOS scores, indicating that patients with a greater degree of hindbrain pathology respond better to surgery. The proposed points-based algorithm has good predictive value for postoperative multifactorial outcome in these patients.

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Background The optimal management and the role of surgery in monomelic amyotrophy, also known as Hirayama disease (HD), remain controversial. In the largest series of patients with HD managed by cervical duraplasty (CD), this study compares the outcomes between conservative and surgical management. Methods A retrospective case–control study was performed on 60 patients with HD. The cases consisted of 30 patients who underwent CD, and 30 age- and sex-matched controls who managed with long-term collar wear. Clinical improvement was recorded using two patient-reported outcome measures—the Odom's scale and a self-rated hand grip strength score. Median and ulnar compound muscle action potential (CMAP) amplitudes and various magnetic resonance imaging parameters were recorded. Results None of the controls experienced clinical improvement at follow-up; 90% remained status quo at 24.33 ± 9.38 months. Seventy-six percent of the operated patients demonstrated clinical improvement at 29.61 ± 12.78 months, and a majority of them reported moderately better grip strength. The preoperative anteroposterior diameter (APD) of the surgical group improved from 0.74 ± 0.13 to 0.86 ± 0.21 (p = 0.01), and the cord demonstrated a significant decrease in forward migration on flexion (0.20 ± 0.11 and 0.03 ± 0.07 preoperatively and at follow-up, respectively, p < 0.0001). Patients with clinical improvement demonstrated significantly better mean APD and median and ulnar CMAP values than those who did not improve (p < 0.0001). The mean cervical alignment did not change significantly at follow-up (p = 0.13). Conclusions This study shows that CD can significantly alter the clinical course of patients with progressive symptoms of HD. This approach successfully arrests the forward migration of the cervical cord on flexion and promotes morphological recovery of the cord. A majority of the patients undergoing CD demonstrate clinical and electrophysiological improvement at mid-term follow-up.