A data-driven approach to define the stages and patterns of neurological recovery after traumatic spinal cord injury.

BACKGROUND: Recovery after spinal cord injury (SCI) follows a complex and variable trajectory, yet the field lacks clear, data-driven definitions of the temporal stages of recovery. This study aimed to model the trajectory of recovery after SCI and define distinct post-injury phases based on real-world clinical data. METHODS: We analyzed longitudinal data from 4407 individuals with traumatic SCI enrolled in the European Multicenter Study about Spinal Cord Injury (EMSCI). Neurological improvement was quantified using the Integrated Neurological Change Score (INCS). Functional recovery was assessed using the Spinal Cord Independence Measure (SCIM) and a derived measure of hand motor function based on motor scores of the C6, C8, and T1 myotomes. Longitudinal recovery trajectories were modeled using random forest regression, locally estimated scatterplot smoothing (LOESS), and neural networks. Lastly, latent class mixed models (LCMM) were employed to identify subgroups with distinct recovery profiles. RESULTS: Across all models, neurological recovery followed a four-stage sigmoidal pattern: an acute phase (up to ∼2 weeks post-injury) with minimal change; a transition phase (∼2 to 9-11 weeks) marked by substantial neurological change; a pre-chronic phase (∼10 weeks to 7-8 months) characterized by ongoing but non-linear recovery; and a chronic phase (beyond ∼7-8 months) in which recovery plateaued. Neurological improvement consistently preceded functional gains captured by SCIM and hand motor strength. Latent class analysis identified four distinct recovery profiles: class 1 (marked recovery), classes 2 and 3 (moderate recovery), and class 4 (minimal to no recovery). Notably, despite significant variability in the magnitude of lower extremity recovery across classes, the timing of the transition phase was remarkably consistent, aligning with the population-level window of approximately 10-11 weeks post-injury. CONCLUSIONS: The majority of neurological and functional improvement occurs within the first ∼10 weeks post-injury. These findings align with the concept of a period of heightened neuroplasticity and provide a data-driven framework for timing assessments and interventions in SCI recovery.