Relationship of MRI to ASIA Impairment Scale in Chronic Spinal Cord Injury

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DESCRIPTION (provided by applicant): The objective of this investigation is two-fold: 1) to add to the classification value of the American Spinal Injury Association (ASIA) Impairment Scale by establishing imaging criteria for chronic spinal cord injury (SCI), 2) to use advanced MR imaging techniques as tools to understand the structural variables that contribute to residual neurological function and the capacity for recovery. A preserved rim of white matter at the injury epicenter characterizes SCI pathology, and the integrity of this tissue determines the amount of preserved function. High resolution imaging is necessary to visualize the subtle structural differences that are responsible for differing levels of function both at the site of and distal to the injury epicenter. Spinal cord imaging is complicated by the small size of the cord, interference from surrounding bone, respiratory and cardiovascular related motion and cerebrospinal fluid pulsation artifacts. Recently, investigators at the F.M. Kirby Research Center for Functional Brain Imaging at Kennedy Krieger Institute have successfully used Diffusion Tensor Imaging (DTI) and Magnetization Transfer (MT) to visualize over sixty injured spinal cords. These imaging techniques are of sufficient resolution and quality to correlate DTI- and MT-derived metrics sensitive to white matter disruption with neurological function in chronic SCI. We address the specific hypothesis that neurological function/deficit clinically defined through the ASIA criteria is related to disordered white matter pathways in persons with chronic SCI through tract specific DTI-derived metrics such as: fractional anisotropy (FA), average diffusion coefficient (MD), parallel and perpendicular eigenvalues (;|| and ;4) and MTCSF (magnetization transfer weighted image normalized by cerebrospinal fluid), but not conventional T1- and T2- weighted imaging. One hundred and twenty individuals divided amongst four ASIA classes (ASIA A-C and E) will be imaged using conventional (T1, T2) and advanced (DTI, MT) MRI techniques. The integrity of white matter both at the site of and distal to the epicenter of the lesion in these subjects will be defined in a tract specific manner using DTI and MT and will be tested for relationships to ASIA clinical classification and neurological motor and sensory testing (Aim1) and to quantitative vibration threshold sensory testing (Aim2). PUBLIC HEALTH RELEVANCE: It is known that the amount of residual spinal cord function after injury is related to the composition and health of the white matter that remains at the level of injury, but currently it is not known exactly how much preservation of the white matter tracts is necessary for neurological function. Development of high resolution, non-invasive imaging methods to determine the integrity of white matter after injury is important for designing and testing restorative treatments for individuals living with SCI. We propose to apply recently improved advanced magnetic resonance imaging (MRI) methods to quantify white matter integrity in the spinal cord and relate the information obtained to the motor and sensory function scores assessed by the American Spine Injury Association (ASIA) Impairment Scale.