Introduction

Neurodegenerative diseases include a broad group of disorders affecting the central nervous system (CNS) that are characterized by gradually progressive death or dysfunction of neurons. The etiology of many of these disorders is unknown, although various genetic factors as well as largely unidentified environmental factors may play a role in some. The basic cellular mechanisms responsible for the neuronal loss in neurodegenerative disease are also largely unknown. There is evidence that some disorders may be related to inappropriate activation of the apoptotic pathways that are involved in programmed cell death. There is a wide range of clinical manifestations of neurodegenerative disease, since the salient features of a particular disease are closely related to the functions of the specific group of neurons that has been affected.

For the most part, the diagnosis of a neurodegenerative disease is based on the presence of a characteristic neurological syndrome and the major role of routine neuroimaging techniques, including conventional MRI sequences, has been to exclude other disorders that may be a source of diagnostic confusion. The continuing evolution of new techniques for imaging the CNS, however, has produced significant advances in our understanding of the changes in brain structure and function associated with neurodegenerative disease. A non-invasive tool with the potential to monitor disease progression from a very early stage could have a profound impact on the management of these debilitating disorders. Such techniques may provide an improved understanding of the mechanisms underlying the inexorable neuronal loss that characterizes neurodegenerative disorders. In addition, by providing an objective method to monitor disease progression, they may provide an important tool in evaluating the efficacy of new therapeutic approaches.