Using Muscle Functional MRI to Study Spatial Muscle Activation Patterns in People With SCI

Several intervention modalities including locomotor training and neuromuscular stimulation have demonstrated the ability to promote neuromuscular recovery following both motor complete and motor incomplete spinal cord injury. While an array of methodologies and technologies exist for evaluating different aspects of recovery - for instance, stabilometry to assess balance and DEXA to assess bone mineral density - there remains a need for a means to comprehensively study spatial changes to muscle activation. Electromyography (EMG) provides temporal information for muscle firing during activity; however, it has several important limitations. While surface EMG (sEMG) is relatively easily collected, it cannot collect information on deep muscles and is susceptible to cross-talk - i.e. signals originating from muscles other than those intended to be studied. Fine wire intramuscular EMG is available but is invasive, and both sEMG and fine wire EMG suffer from reliability issues related to sensitivity to exact placement of electrodes and changes in skin conductivity.

In this project the investigators propose to investigate the potential for muscle functional MRI (mfMRI) techniques to study changes in spatial patterns of neuromuscular activation associated with spinal cord injury (SCI). mfMRI imaging focuses on the time for relaxation of transverse magnetization (T2) of water in muscle, which has been found to be increased, i.e. prolonged, with exercise of the muscle. The phenomenon is understood to be related to an accumulation of osmolytes (phosphate, lactate, and sodium) in the muscle water. In our literature search the investigators have not found reports of mfMRI used to observe differences in activation in people with SCI, nor in any other neurological population. For all imaging in our study, participants will perform supine quadriceps leg raise exercises on the detachable MRI table outside the scanner. They will then be transported into the MRI scan chamber for T2 scanning of the thigh muscles. Sessions will start with several minutes of rest and baseline imaging to collect resting state T2, with exercise related T2 shifts to be calculated relative to this. Segmentation of the four quadriceps muscles on each slice will be used to describe the overall activation of each muscle. The investigators will perform a cross sectional study comparing T2 shift muscle activation values between people with motor incomplete SCI and a control group without SCI. The investigators hypothesize that people with SCI will have lower T2 shift values and less uniform muscle activation than able bodied controls. Successful completion of this study will provide new information on spatial muscle activation patterns in SCI and produce knowledge to point the way to more widespread application of the technique.

Inclusion criteria

SCI group Inclusion criteria

• Age: 18-50 yrs
• BMI <35 kg/m2
• Chronic injury (at least 1 year post injury)
• Neurological injury status: Incomplete motor and sensory SCI classified with ASIA Impairment Scale C or D
• Ambulatory status: Participants must be nonambulatory. Individuals who can stand or walk even a few steps with or without assistance will not be eligible to participate
• Ability to flex and extend at least one knee joint under volitional control:

• without stimulation or assistance
• full range of motion not required
• ability to move against gravity not required Able bodied group Inclusion criteria
• Age: 18-50 yrs
• BMI <35 kg/m2

Exclusion criteria

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