Sensorimotor cortical activation in patients with cervical spinal cord injury with persisting paralysis.

BACKGROUND: It is well documented that cortical sensorimotor representations are altered following nervous system pathology. However, little is known about these representations over time and, more specifically, in paralyzed individuals.
OBJECTIVE: To investigate the temporal changes in sensorimotor cortical activation in paralyzed individuals following spinal cord injury (SCI).
METHODS: Functional MRI (fMRI) was used to study 4 tetraplegic individuals repeatedly over the first year following traumatic SCI as well as 7 healthy individuals, 3 repeatedly. During fMRI, controls performed ankle movements, and patients attempted them. Standard clinical measures of SCI were used to assess movement ability.
RESULTS: Shortly after SCI, activation within the primary motor cortex (M1) was present at levels similar to those in controls. Extensive associated cortical sensorimotor activation, not seen in controls, was present. Over time, as paralysis persisted, activation in M1 was significantly reduced and progressively decreased in associated cortical sensorimotor areas. No session-specific dependence in M1 or associated sensorimotor cortical activation was found in healthy individuals.
CONCLUSIONS: These findings provide the first report of the temporal evolution of cortical sensorimotor fMRI activation following traumatic SCI in humans who do not recover movement. Coupled with findings in patients who recover post-SCI, our results suggest an association between motor task-related fMRI activation and degree of motor function postinjury. Understanding the time course of plasticity and the relationship between cortical sensorimotor activation and motor ability following SCI could allow assessment of rehabilitation potential, monitoring of therapeutic efficacy, and improvement in therapeutic intervention along the course of recovery.