The Role of Advanced Magnetic Resonance Imaging

Multiple sclerosis (MS) is thought to be an autoimmune disease in which inflammatory demyelination is triggered by T lymphocytes and followed by axonal degeneration. Accumulating evidence suggests that axonal pathology may be a principal early step in the pathophysiology of MS. Axonal degeneration has been observed in normal-appearing white matter from patients with MS. Cortical lesions undergo demyelination and axonal transection in the absence of a classic inflammatory response. These and other observations have led some researchers to suggest that MS may be a primary neurodegenerative disease with superimposed inflammation. A variety of neuroimaging techniques are available for the assessment of MS pathology, each of which has its own advantages and limitations. Two magnetic resonance imaging techniques are especially useful for the assessment of neurodegeneration and neuroregeneration in MS. Magnetization transfer imaging provides a marker of central nervous system myelin and axonal density that can be used to study the effects of disease-modifying therapy in patients with MS. Diffusion-weighted imaging, which measures the random motion of water molecules in tissue, may be used to distinguish changes in myelination and axonal density. Cerebral atrophy is a useful marker of axonal loss that has been used extensively in clinical trials of MS treatment. (Adv Stud Med. 2008;8(9):309-314)