MRI Aspects: Conventional, SWI, DTI

Abstract

Despite the good quality of new generation computerized tomography (CT), magnetic resonance imaging (MRI) is the method of choice for visualization of structures within the posterior fossa and spinal canal. Different to CT bone artefacts are not a problem in MRI. The cerebellum, the brainstem and the spinal cord are shown in much more detail. This chapter will focus on structural MRI in degenerative cerebellar ataxias. These are slowly progressive degenerative disorders which involve the cerebellum and cerebellar pathways to varying extents. Structural MRI in focal cerebellar disease, such as stroke, tumors or multiple sclerosis, will not be addressed. T1 weighted MRI images have the best gray matter/white matter contrast. Therefore, T1 weighted MRI images are commonly used to reveal atrophy of the cerebellar cortex, the brainstem and spinal cord. In a subset of cerebellar ataxias there is white matter disease. Proton density (PD), T2 weighted, and fluid attenuated inversion recovery (FLAIR) MRI images are sensitive to show white matter lesions. MRI contrast enhancement is uncommon in cerebellar degeneration. Susceptibility weighted imaging (SWI) and diffusion weighted imaging (DWI), more specifically diffusion tensor imaging (DTI), are newer developments. SWI images are helpful to show abnormal brain iron deposition, but also accompanying atrophy of the iron-rich cerebellar nuclei. DTI is helpful to show changes of the integrity of cerebellar white matter and cerebellar peduncles.