Imaging evaluation of demyelinating processes of the central nervous system

Demyelinating processes involving the central nervous system have a variety of aetiologies and can be separated into primary and secondary demyelinating processes. The classic example of primary demyelination is multiple sclerosis. Secondary demyelination, where the aetiology is known, includes infectious, metabolic and toxic disease processes. The underlying component of all demyelinating disorders is damage to the myelin sheath and/or the oligodendrocyte, the cell forming the myelin sheath. These processes often have similar imaging findings, making knowledge of the patient's history, physical examination and laboratory evaluation imperative for developing a differential diagnosis. This pictorial essay provides a review of the imaging of these diverse disorders.