• Naosuke Kamei, Toshio Nakamae, Toshiaki Maruyama, Kazuto Nakao, Fadlyansyah Farid, Hiroki Fukui, and Nobuo Adachi.
• Department of Orthopaedic Surgery, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
• Spine. 2024 Dec 1; 49 (23): E387E393E387-E393.

Study DesignA retrospective case-control study.ObjectiveTo characterize the motor evoked potential (MEP) when the epiconus or conus medullaris is compressed by a fracture of the T12 or L1 vertebra.Summary Of Background DataAlthough the characteristics of compressive cervical and thoracic myelopathy with transcranial magnetic stimulation MEP have been reported, the MEP parameters in compressive disorders of the epiconus and conus medullaris have not yet been characterized.MethodsTwenty patients with T12 or L1 vertebral fractures who had lower extremity symptoms due to compression of the epiconus or conus medullaris were included. These patients were compared with 28 healthy controls and 32 patients with cervical spondylotic radiculopathy (CSR) without spinal cord compression. MEPs of abductor hallucis muscles were recorded using transcranial magnetic stimulation and electrical stimulation of the tibial nerve. MEP latency, central motor conduction time (CMCT), and peripheral conduction time (PCT) were evaluated.ResultsMEP latency, CMCT, and PCT were significantly longer in patients with fractures than in healthy controls and patients with CSR. MEP latency was most accurate for differentiating patients with fracture from healthy controls (cutoff value, 40.0 ms, sensitivity, 95.0%; specificity, 100%), and CMCT was most accurate for comparing patients with fracture and CSR (cutoff value, 15.5 ms, sensitivity, 80.0%; specificity, 93.8%). In the distinction between patients with fracture and CSR, 16 of the 20 patients with fracture exceeded the cutoff values for any of the parameters, and 12 of them exceeded the cutoff values for all parameters. There was no significant correlation between the linear distance from the most inferior end of the spinal cord to the site of compression and any of the MEP parameters.ConclusionBoth CMCT and PCT are often prolonged in compressive lesions of the epiconus and conus medullaris, and MEP latency and CMCT are useful in the diagnosis.Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.

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