Background: Magnetic resonance imaging (MRI) has revolutionized the diagnosis and management of patients with multiple sclerosis (MS). Metrics derived from conventional MRI are now routinely used to detect therapeutic effects and extend clinical observations. Conventional MRI measures have insufficient sensitivity and specificity to reveal the true degree of pathologic changes occurring in MS. T2-weighted and T1-weighted imaging cannot distinguish between inflammation, edema, demyelination, Wallerian degeneration, and axonal loss. Nonconventional MRI techniques are now emerging and proving to be more related with the most disabling features of MS.
Review summary: The large variety of MRI metrics presently available are summarized, including measurement of T1-weighted hypointense lesions, central nervous system atrophy, magnetization transfer imaging, myelin water fraction, diffusion tensor imaging, magnetic resonance spectroscopy, and susceptibility-weighted imaging. The most up-to-date MRI techniques and their relationship with central nervous system pathology are described, and a comprehensive overview of the use of MRI in patients with MS is offered.
Conclusions: Advanced MRI techniques provide a better understanding of the pathologic processes that most likely are related to disease activity and clinical progression. Such metrics are able to reveal a range of tissue changes that include demyelination, axonal loss, iron deposition, and neurodegeneration and they provide the evidence that important occult pathology is occurring in the normal appearing white and gray matter. Despite these promising results none of these techniques have been adopted in the MRI consensus guidelines for imaging of the brain and spinal cord in patients with MS due to lack of standardization.