Incidence Rates and Diagnostic Trends of Perioperative Acute Transverse Myelitis in Patients Who Underwent Surgery for Degenerative Spinal Diseases: A Nationwide Epidemiologic Study of 201,769 Patients

<b>Background</b>: Acute transverse myelitis (ATM) can closely mimic degenerative spinal disorders, often leading to diagnostic delay or inappropriate surgical decisions. However, its epidemiologic characteristics among patients undergoing spinal surgery remain unknown. This nationwide, population-based study investigated the incidence, perioperative diagnostic trends, and risk factors of ATM in patients treated surgically for degenerative spinal disease. <b>Methods</b>: Data were extracted from the Korean Health Insurance Review and Assessment Service database (2014-2018). Adults (>19 years) who underwent surgery for degenerative spinal disease were identified, and those with malignancy, infection, fracture, or prior myelitis were excluded. The two-year perioperative observation period (-360 to +360 days) was divided into 24 consecutive 30-day intervals. Patients were classified by ATM occurrence, and multivariable logistic regression with bootstrap validation was used to identify independent risk factors. Incidence rates were expressed per 100,000 person-years. <b>Results</b>: Among 201,769 eligible patients, 269 (0.13%) developed ATM, yielding an incidence of 67 (95% CI: 59-75) per 100,000 person-years-substantially higher than in the general population. Younger age, male sex, myocardial infarction, cerebrovascular disease, rheumatologic disease, and cervical or thoracic spinal lesions were independent predictors. Notably, 28.3% of ATM cases were diagnosed within 30 days before surgery, and 50.9% within the four-month window from three months preoperatively to one month postoperatively, indicating a marked temporal clustering around surgery. <b>Conclusions</b>: ATM occurred far more frequently among patients undergoing surgery for degenerative spinal disease than in the general population, with diagnoses peaking immediately before surgery. This pattern likely reflects diagnostic delay rather than true perioperative onset. Because ATM can clinically and radiologically resemble degenerative myelopathy, clinicians should maintain a high index of suspicion in patients presenting with atypical or rapidly progressive neurological deterioration. Early recognition may prevent unnecessary surgery and improve neurological outcomes.