Significance of MRI in diagnosis and differential diagnosis of Parkinson's disease.

The differential diagnosis of parkinsonian syndromes is considered one of the most challenging in neurology, even for movement disorder specialists. Despite published consensus operational criteria for the diagnosis of Parkinson's disease (PD) and the various atypical parkinsonian disorders (APDs) such as progressive supranuclear palsy, multiple system atrophy, and corticobasal syndrome, the clinical separation of APDs from PD carries a high rate of misdiagnosis. However, an early differentiation between APD and PD, each characterized by a largely different natural history, is crucial for determining the prognosis and choosing a treatment strategy. Despite limitations, the different modern magnetic resonance (MR) techniques have undoubtedly added to the differential diagnosis of neurodegenerative parkinsonism. Conventional MRI with visual assessment of T(2)- and T(1)-weighted imaging as well as various advanced MRI techniques offer objective measures and may therefore be useful tools in the diagnostic workup of PD and APDs. In clinical practice, conventional MRI is a well-established method for the exclusion of symptomatic parkinsonism due to other pathologies such as tumors, cerebral ischemia or inflammatory diseases. Furthermore, over the past two decades, advances in MR techniques have enabled to quantitatively illustrate abnormalities in the basal ganglia and infratentorial structures in APDs by methods such as magnetic resonance volumetry, diffusion-weighted imaging, magnetization transfer imaging and proton magnetic resonance spectroscopy. This article aims to review research findings on the value of MRI techniques in the differential diagnosis of neurodegenerative parkinsonian disorders.