Structural and functional magnetic resonance imaging in neurodegenerative diseases

Abstract

Introduction A full account of structural and functional MRI in neurodegenerative diseases would require an extensive volume. There are many neuroradiology texts which describe the common structural MRI abnormalities. MRI acquisition and processing techniques continue to develop apace and this chapter focuses on non-routine structural MRI and functional MRI (fMRI). We define neurodegenerative diseases as having a distinct clinical picture, progressive natural history, focal or global pathology, and characteristic histopathology. This chapter describes diseases where neurodegeneration occurs intracranially, rather than in the spinal cord or peripheral nervous system. We do not include diseases where neurodegeneration occurs secondary to vascular or inflammatory processes, so we exclude diseases such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, multiple sclerosis or complex biochemical disorders (e.g. leukodystrophies), but we do include some disorders of copper, iron and calcium metabolism as well as prion diseases. Accepting our limitations, we limit our discussion to five categories of neurodegenerative disorders: [i] dementias, [ii] extrapyramidal disorders, [iii] motor system disorders, [iv] ataxias and [v] prion diseases. Of these, the application of non-routine MRI and fMRI to dementia and movement disorders has seen the largest expansion so far. Structural MRI in neurodegenerative disorders Structural MRI acquisition and postprocessing techniques Typical routine clinical sequences, such as T 1 and T 2 -weighted, fluid attenuated inversion recovery (FLAIR) and Short Tau Inversion Recovery (STIR) are effective at showing the location of pathological changes, but are seldom specific for the type of pathology. For this reason newer MRI techniques are being developed.