• R Dinesh Iyer, Karthik Ramachandran, Pranavakumar Palaninathan, Ajoy Prasad Shetty T, Sri Vijayanand K S, Rishi Mugesh Kanna, and Shanmuganathan Rajasekaran.
• Department of Orthopaedics and Spine Surgery, Ganga Medical Centre and Hospitals Pvt. Ltd., Coimbatore, India.
• World Neurosurg. 2024 Oct 1; 190: e17e25e17-e25.

ObjectiveTo analyze intraoperative neuromonitoring data of patients with degenerative cervical myelopathy undergoing cervical laminectomy and assess the incidence of signal drops and their risk factors.MethodsThis retrospective observational study included patients with degenerative cervical myelopathy who underwent cervical laminectomy with intraoperative neuromonitoring between July 2018 and March 2023. We analyzed the signal changes for any correlation with the type of pathology (ossified posterior longitudinal ligament vs. cervical spondylotic myelopathy [CSM]) and clinical (severity of myelopathy, duration of symptoms) and radiological (length of cord signal changes and K-line) parameters.ResultsOf 100 degenerative cervical myelopathy cases, 55 were diagnosed as OPLL and 45 as CSM. Signal drops were recorded in 26 patients-14 persistent drops and 12 transient drops. True positive drops were seen in 4 patients (2 OPLL and 2 CSM), 3 of whom had sustained bimodal drops (both somatosensory evoked potentials and motor evoked potentials). Signal drops were significantly more frequent with OPLL compared with CSM (P < 0.01). Ten of 14 persistent signal drops and 9 of 12 transient drops were seen in patients in OPLL. Continuous OPLL, negative K-line, hill type OPLL, severity of myelopathy, and longer duration of symptoms were risk factors for signal drops.ConclusionsPatients with cervical OPLL have a higher incidence of false positive and transient signal drops after decompression compared with patients with CSM. Longer duration of symptoms, high-grade myelopathy, continuous OPLL, hill type OPLL, and negative K-line were risk factors for signal drops.Copyright © 2024 Elsevier Inc. All rights reserved.

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