• Hitoshi Yamahata, Satoshi Yamaguchi, Toshiya Osanai, Masaaki Takeda, Takafumi Mitsuhara, Masanao Mori, Shunichi Tanaka, Masanori Yonenaga, Akira Taguchi, Yosuke Watanabe, Masaru Abiko, Toshitaka Seki, Toru Sasamori, Kazunori Arita, and Koji Yoshimoto.
• Department of Neurosurgery, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan. Electronic address: yamahata-nsu@umin.net.
• World Neurosurg. 2019 Oct 1; 130: e1020-e1027.

BackgroundBecause spinal dural arteriovenous fistulae (SDAVF) are rare and their clinical presentation is nonspecific, they are often overlooked during diagnostic evaluations. Typical magnetic resonance imaging (MRI) findings are intramedullary T2-weighted signal hyperintensity and perimedullary flow voids. There are few reports on the characteristic signs of the cauda equina. We assessed the significance of a new imaging parameter, the cauda equina occupation ratio (CEOR), for the evaluation of SDAVF.MethodsWe retrospectively analyzed the clinical charts and radiological findings of 20 SDAVF patients treated at our institutions. We evaluated sagittal T2-weighted MRI scans and assessed the CEOR, the occupation ratio of the cauda equina compared to the sagittal diameter of the corresponding lumbar spinal canal. The controls were 21 age- and sex-matched subjects.ResultsOf the 20 SDAVF, 10 were at the thoracic and 10 at the lumbar spine. There was no significant difference between the preoperative CEOR and the spinal level of the fistulae or the neurological signs. On preoperative MRI scans, the mean CEOR was 56.0 ± 7.8; postoperatively, it was 37.1 ± 7.4 (P = 0.000). The preoperative CEOR was significantly larger in SDAVF patients than in the controls (P = 0.000); postoperatively, it was smaller than in the controls (P = 0.14).ConclusionsThe preoperative CEOR was larger in patients with SDAVF than in the controls. It normalized after successful occlusion of the fistula. Our findings indicate that the CEOR is a useful parameter for the pre- and postoperative evaluation of SDAVF.Copyright © 2019 Elsevier Inc. All rights reserved.

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