Correlation Between Results from a New Magnetic Resonance Imaging Technique to Measure Myelin in the Spinal Cord and Somatosensory Evoked Potentials

Magnetic resonance imaging (MRI) is a powerful non-invasive imaging tool due to its ability to provide soft tissue contrast with high spatial resolution. Clinicians and researchers alike value MR images both for diagnosis and characterization of changes cause by disease. Recent advances have been made using MRI to image central nervous system white matter and investigate diseases that affect the white matter (such as Multiple Sclerosis), and damage to the spinal cord. The term “white matter” is derived from the white colour of nerve tracts. It appears white because of the layers of fat wrapped around each nerve fibre, called the “myelin sheath”. If the myelin sheath has been degraded or broken down, transmission of information along the fibre can be slowed down or lost completely. In the case of a narrowing of the spinal canal, the invertebral discs slip out of place and put pressure on the spinal cord, damaging the white matter tracts, resulting in symptoms like a feeling of numbness or tingling in the hands or feet. Somatosensory evoked potentials (SSEP) are a current clinical tool used to detect myelin degradation and nerve damage in the spinal cord. However, SSEP measurements are limited to only sensory pathway nerves, and cannot locate damage throughout the entire spinal cord. The UBC MRI Research Group has recently developed an MRI technique to measure myelin content in vivo, termed “myelin water imaging” (MWI), which can be applied throughout the brain and spinal cord. Erin MacMillan is applying the MWI technique to healthy adults and people suffering from narrowing of the cervical spinal canal. She hopes to find that MWI provides results consistent with SSEP measurements in sensory pathways, and identifies myelin degradation throughout the cervical spine. In addition, she will compare patient results from before and after surgery in the hopes of finding that the white matter has been repaired. If MWI proves to be an accurate measurement of myelin in the spinal cord, it could potentially be used to track myelin content during new spinal cord injury treatments aimed at degrading myelin in an effort to encourage nerve fibre repair.