Brain magnetic resonance imaging techniques in the diagnosis of parkinsonian syndromes.

Parkinson disease (PD) is the most common neurodegenerative cause of parkinsonism, followed by progressive supranuclear palsy and multiple system atrophy (MSA). Despite published consensus operational criteria for the diagnosis of PD and the various atypical parkinsonian disorders (APD) such as progressive supranuclear palsy, Parkinson variant of MSA, and corticobasal degeneration, differentiation of these clinical entities may be challenging, particularly in the early stages of the disease. Diagnosis of PD and its distinction from APD and symptomatic parkinsonism is crucial for the clinical evaluation, as these disorders differ in prognosis, treatment response, and molecular pathogenesis. Despite limitations the different modern magnetic resonance (MR) techniques have undoubtedly added to the differential diagnosis of neurodegenerative parkinsonism. This article focuses on static or structural conventional MR imaging techniques including standard T2-weighted, T1-weighted, and proton-density sequences, as well as different advanced techniques, including methods to assess regional cerebral atrophy quantitatively such as magnetic resonance volumetry, diffusion tensor and diffusion-weighted imaging, and magnetization transfer imaging, to assist in the differential diagnosis of neurodegenerative parkinsonian disorders.