Disability, atrophy and cortical reorganization following spinal cord injury

Abstract

The impact of traumatic spinal cord injury on structural integrity, cortical reorganization and ensuing disability is variable and may depend on a dynamic interaction between the severity of local damage and the capacity of the brain for plastic reorganization. We investigated trauma-induced anatomical changes in the spinal cord and brain, and explored their relationship to functional changes in sensorimotor cortex. Structural changes were assessed using cross-sectional cord area, voxel-based morphometry and voxel-based cortical thickness of T1-weighted images in 10 subjects with cervical spinal cord injury and 16 controls. Cortical activation in response to right-sided (i) handgrip; and (ii) median and tibial nerve stimulation were assessed using functional magnetic resonance imaging. Regression analyses explored associations between cord area, grey and white matter volume, cortical activations and thickness, and disability. Subjects with spinal cord injury had impaired upper and lower limb function bilaterally, a 30% reduced cord area, smaller white matter volume in the pyramids and left cerebellar peduncle, and smaller grey matter volume and cortical thinning in the leg area of the primary motor and sensory cortex compared with controls. Functional magnetic resonance imaging revealed increased activation in the left primary motor cortex leg area during handgrip and the left primary sensory cortex face area during median nerve stimulation in subjects with spinal cord injury compared with controls, but no increased activation following tibial nerve stimulation. A smaller cervical cord area was associated with impaired upper limb function and increased activations with handgrip and median nerve stimulation, but reduced activations with tibial nerve stimulation. Increased sensory deficits were associated with increased activations in the left primary sensory cortex face area due to median nerve stimulation. In conclusion, spinal cord injury leads to cord atrophy, cortical atrophy of primary motor and sensory cortex, and cortical reorganization of the sensorimotor system. The degree of cortical reorganization is predicted by spinal atrophy and is associated with significant disability.

Clinical correlates of cerebral diffusion tensor imaging findings in chronic traumatic spinal cord injury

“…23,24 We did not find any significant differences in the DTI metrics between SCI patients and controls in these structures. Freund et al 14 and Guleria et al 15 showed reduced FA values but unchanged MDs in the PLIC after SCI compared with healthy subjects. Guleria et al 15 reported a progressive increase in the FA values in the PLIC and corona radiata up to 12 months after injury.…”

“…Freund et al 14 and Guleria et al 15 showed reduced FA values but unchanged MDs in the PLIC after SCI compared with healthy subjects. Guleria et al 15 reported a progressive increase in the FA values in the PLIC and corona radiata up to 12 months after injury. FA values in the corona radiata were eventually higher in subjects with SCI compared with the controls.…”

“…In a study by Guleria et al, 14 alterations in DTI metrics suggesting retrograde degeneration after SCI were shown along the corticospinal tract in the medulla, pons, midbrain and PLIC. Freund et al 15 observed a reduction in the FA in patients with SCI in the pyramids and the PLIC. Although there were no significant differences in FA values at the level of the cerebral peduncles, axonal degeneration and demyelination -related alterations in directional diffusivities were noted.…”

“…This finding is in agreement with previous studies. 5,15 There was a moderate association between macroscopic posttraumatic changes in the spinal cord and microstructural changes in the centrum semiovale. An increase in ADC in the posterior part of the centrum semiovale was positively correlated with the craniocaudal length of the spinal cord lesion.…”

“…However, these studies consisted of relatively small samples and primarily included subjects with complete SCI. 5,14,15 The purpose of this study was to quantitatively assess the state of the cerebral white matter tracts in chronic traumatic SCI using DTI in a generalizable sample of patients with both clinically complete and incomplete SCI. We also investigated the association of DTI values with clinical neurological deficit.…”