Onset timing and recovery patterns in segmental motor paralysis following anterior cervical spine surgery: a multicenter study of the risk factors for persistent paralysis

BACKGROUND CONTEXT: Segmental motor paralysis is a well-recognized complication following anterior cervical spine surgery. While risk factors have been identified, little is known about the factors that influence recovery outcomes, and there has been no systematic analysis of the relationship between onset timing and recovery patterns. PURPOSE: This study aimed to investigate the clinical course of segmental motor paralysis after anterior cervical spine surgery, identify risk factors for persistent paralysis, and determine the relationship between paralysis onset timing and recovery patterns. STUDY DESIGN/SETTING: This multicenter, retrospective cohort study was conducted at 3 spine centers affiliated with the Institute of Science Tokyo Group between January 2011 and March 2021. PATIENT SAMPLE: Among the 1,428 patients who underwent anterior cervical procedures with complete 2-year follow-up data available, 93 patients who developed segmental motor paralysis after anterior cervical spine surgery were identified who met the inclusion criteria. OUTCOME MEASURES: Recovery was defined as a return to preoperative muscle strength, as determined by manual muscle testing. Independent risk factors for persistent paralysis were identified using multivariate logistic regression analysis. Patients were categorized into onset time groups of day 0, day 1, days 2 to 4, and day 5 or later. METHODS: Clinical and operative characteristics were compared between recovery and nonrecovery groups. Muscle strength recovery patterns were analyzed over 2 years. Risk factors for persistent paralysis were determined through univariate and multivariate analyses. No external funding was received for this study, and the authors report no study-specific conflicts of interest. RESULTS: At 2-year follow-up, persistent paralysis had occurred in 18 (19.4%) patients. Day 1 onset demonstrated the highest nonrecovery rate at 42.1% compared to 10.7% to 21.1% for other onset times (p=.044). Independent risk factors for persistent paralysis included a lower manual muscle testing score at onset (OR 7.38, p<.001) and a greater number of surgical levels (OR 1.86, p=.032). CONCLUSIONS: This first systematic analysis reveals that paralysis onset on day 1 after anterior cervical spine surgery is associated with a poorer prognosis. Initial muscle weakness severity and multilevel surgery are key predictors of persistent paralysis. These findings may inform future preventive strategies.