Postoperative diffusion-weighted imaging and neurological outcome after convexity meningioma resection

OBJECTIVE Convexity meningiomas are commonly managed with resection. Motor outcomes and predictors of new deficits after surgery are poorly studied. The objective of this study was to determine whether postoperative diffusionweighted imaging (DWI) was associated with neurological deficits after convexity meningioma resection and to identify the risk factors for postoperative DWI restriction. METHODS A retrospective review of patients who had undergone convexity meningioma resection from 2014 to 2018 was performed. Univariate and multivariate logistic regressions were performed to identify variables associated with postoperative neurological deficits and a DWI signal. The amount of postoperative DWI signal was measured and was correlated with low apparent diffusion coefficient maps to confirm ischemic injury. RESULTS The authors identified 122 patients who had undergone a total of 125 operations for convexity meningiomas. The median age at surgery was 57 years, and 70% of the patients were female. The median follow-up was 26 months. The WHO grade was I in 62% of cases, II in 36%, and III in 2%. The most common preoperative deficits were seizures (24%), extremity weakness/paralysis (16%), cognitive/language/memory impairment (16%), and focal neurological deficit (16%). Following resection, 89% of cases had no residual deficit. Postoperative DWI showed punctate or no diffusion restriction in 78% of cases and restriction > 1 cm in 22% of cases. An immediate postoperative neurological deficit was present in 14 patients (11%), but only 8 patients (7%) had a deficit at 3 months postoperatively. Univariate analysis identified DWI signal > 1 cm (p < 0.0001), tumor diameter (p < 0.0001), preoperative motor deficit (p = 0.0043), older age (p = 0.0113), and preoperative embolization (p = 0.0171) as risk factors for an immediate postoperative deficit, whereas DWI signal > 1 cm (p < 0.0001), tumor size (p < 0.0001), and older age (p = 0.0181) were risk factors for deficits lasting more than 3 months postoperatively. Multivariate analysis revealed a DWI signal > 1 cm to be the only significant risk factor for deficits at 3 months postoperatively (OR 32.42, 95% CI 3.3-320.1, p = 0.0002). Further, estimated blood loss (OR 1.4 per 100 ml increase, 95% CI 1.1-1.7, p < 0.0001), older age (OR 1.1 per year older, 95% CI 1.0-1.1, p = 0.0009), middle third location in the sagittal plane (OR 16.9, 95% CI 1.3-216.9, p = 0.0026), and preoperative peritumoral edema (OR 4.6, 95% CI 1.2-17.7, p = 0.0249) were significantly associated with a postoperative DWI signal > 1 cm. CONCLUSIONS A DWI signal > 1 cm is significantly associated with postoperative neurological deficits, both immediate and long-lasting. Greater estimated blood loss, older age, tumor location over the motor strip, and preoperative peritumoral edema increase the risk of having a postoperative DWI signal > 1 cm, reflective of perilesional ischemia. Most immediate postoperative deficits will improve over time. These data are valuable when preoperatively communicating with patients about the risks of surgery and when postoperatively discussing prognosis after a deficit occurs.