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An examination of the relationship between neural plasticity and functional recovery after human spinal cord injury: a spinal cord fMRI study 2011

General Spine

Rachael, L., Bosma
David, W., Cadotte, Non ASSR Member
Christopher, A., Kidd, Non ASSR Member
Karen, Smith, Non ASSR Member
Michael, G., Fehlings, Non ASSR Member
Patrick, W., Stroman, Non ASSR Member

Poster

Purpose

Functional outcomes after spinal cord injury (SCI) are diverse and, depending on the severity of the injury, can result in transient or permanent changes in sensorimotor function. Currently, our understanding of the mechanisms that promote recovery is incomplete. Moreover, conventional measures of sensory and motor ability are not sufficiently sensitive to assess the complex, underlying adaptive neural changes that result in neurobehavioral recovery following injury. Spinal functional magnetic resonance imaging (fMRI) can be used to produce reliable maps of neural function and may therefore enable non-invasive and thorough assessment of patients after SCI. The objective of this study was to map the spinal cord function in order to reveal the full extent of functional changes that occur as a result of trauma and to relate the fMRI results to conventional measures of sensorimotor ability. We hypothesize that spinal fMRI after spinal cord injury demonstrates specific and identifiable changes in local processing in the spinal cord, and in ascending and descending input to/from the brainstem and cortex and that these changes will correspond with functional outcomes.

Methods & Materials

Functional spinal cord MRI data were acquired using a 3T Siemens Magnetom Trio and a 3T GE system from patients with cervical SCI (9 ASIA E and 10 ASIA A, B C) and 20 controls using an fMRI protocol previously described (1,2,3). Thermal stimulation of 4 different sensory dermatomes was applied by means of a custom-made device. This device controls heating and passive cooling of four thermodes to a pre-set stimulation temperature of 44 °C during stimulation, in four linearly-independent block-design paradigms to enable the distinct response to each stimulus to be determined. The four thermodes were placed symmetrically on the right and left sides, on sensory dermatomes corresponding to approximately two spinal cord segments above, and below, the injury level. Data were spatially normalized and analyzed using the general linear model (P=0.0001) and calculations of functional connectivity were conducted (R > 0.5). Spinal fMRI data were correlated with clinical sensory and motor outcomes assessments (ASIA sensory score and FIM).

Results

Activity was detected in the spinal cord and brainstem corresponding to each of the 4 dermatomes that were stimulated, and demonstrated a dependence on the severity of injury. In healthy control subjects, consistent connectivity was detected between the ipsilateral dorsal horn corresponding to each thermal stimulus, and areas of the thalamus, the dorsolateral pontine tegmentum (DLPT) and the rostral medulla midbrain. Patients with ASIA E classifications (ie injured patients who recover to normal function) demonstrated changes in functional responses compared to healthy uninjured controls, despite the absence of neurological deficits. More specifically, for right hand stimulation, activity above the level of injury appeared to be stronger, while fewer connections were evident below the injury suggesting the way by which the spinal cord processes sensory information had changed. Overall, greater consistency of active regions and connectivity was observed in patients with ratings of â