ORIGINAL RESEARCH n NEURORADIOLOGY Radiology: Volume 000: Number 0—   2018 n radiology.rsna.org 1 1 From the Department of Neurosurgery, Regional Cardio- cerebrovascular Center, Seoul National University Bundang Hospital, Seongnam, Korea (S.P.B., T.K., S.U.L., J.S.B., J.H.H., C.Y.K., O.K.K., C.W.O.); and Department of Neuro- surgery, Hangang Sacred Heart Hospital, Hallym University, 12 Beodeunaru-ro 7-gil, Yeongdeungpo, Seoul 07247, Korea (G.H., H.S.B.). Received January 7, 2017; revision requested March 6; revision received June 19; accepted July 15; final version accepted August 14. Address corre- spondence to G.H. (e-mail: storynlemon@gmail.com). Supported by grants from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute funded by the Ministry of Health and Welfare, Republic of Korea (HI16C1197), and the Seoul National University Bundang Hospital (B-1104125005). q RSNA, 2017 Purpose: To evaluate the effect of middle meningeal artery (MMA) embolization on chronic subdural hematoma (CSDH) and compare the treatment outcomes of MMA embolization and conventional treatment. Materials and Methods: All consecutive patients 20 years or older with CSDH were assessed for eligibility. CSDHs with a focal location, a thickness of 10 mm or less, no mass effect, or underlying conditions were excluded. Seventy-two prospectively en- rolled patients with CSDH underwent MMA embolization (embolization group; as the sole treatment in 27 [37.5%] asymptomatic patients and with additional hematoma removal for symptom relief in 45 [62.5%] symptomatic patients). For comparison, 469 patients who underwent conventional treatment were included as a historical con- trol group (conventional treatment group; close, nonsurgi- cal follow-up in 67 [14.3%] and hematoma removal in 402 [85.7%] patients). Primary outcome was treatment fail- ure defined as a composite of incomplete hematoma reso- lution (remaining or reaccumulated hematoma with thick- ness . 10 mm) or surgical rescue (hematoma removal for relief of symptoms that developed with continuous growth of initial or reaccumulated hematoma). Secondary outcomes included surgical rescue as a component of the primary outcome and treatment-related complication for safety measure. Six-month outcomes were compared be- tween the study groups with logistic regression analysis. Results: Spontaneous hematoma resolution was achieved in all of 27 asymptomatic patients undergoing embolization with- out direct hematoma removal. Hematoma reaccumulation occurred in one (2.2%) of 45 symptomatic patients re- ceiving embolization with additional hematoma removal. Treatment failure rate in the embolization group was lower than in the conventional treatment group (one of 72 patients [1.4%] vs 129 of 469 patients [27.5%], respec- tively; adjusted odds ratio [OR], 0.056; 95% confidence interval [CI]: 0.011, 0.286; P = .001). Surgical rescue was less frequent in the embolization group (one of 72 patients [1.4%] vs 88 of 469 patients [18.8%]; adjusted OR, 0.094; 95% CI: 0.018, 0.488; P = .005). Treatment- related complication rate was not different between the two groups (0 of 72 patients vs 20 of 469 patients [4.3%]; adjusted OR, 0.145; 95% CI: 0.009, 2.469; P = .182). Conclusion: MMA embolization has a positive therapeutic effect on CSDH and is more effective than conventional treatment. q RSNA, 2017 Seung Pil Ban, MD Gyojun Hwang, MD, PhD Hyoung Soo Byoun, MD Tackeun Kim, MD Si Un Lee, MD Jae Seung Bang, MD Jung Ho Han, MD Chae-Yong Kim, MD, PhD O-Ki Kwon, MD, PhD Chang Wan Oh, MD, PhD Middle Meningeal Artery Embolization for Chronic Subdural Hematoma 1 This copy is for personal use only. To order printed copies, contact reprints@rsna.org