Differentiation of Parkinson's disease and its related disorders from the view of neuroimaging and neuropathology

Abstract

Parkinson's disease (PD) exhibits motor symptoms such as resting tremor, bradykinesia, and rigidity for which levodopa is successful, but often needs to be differentiated from other PD–related disorders resistant to levodopa. In PD, non–motor symptoms including autonomic symptoms such as constipation, hyperhidrosis, orthostatic hypotension, REM sleep behavior disorder (RBD), psychological symptoms such as depression and apathy, and olfactory dysfunction are merged at a high rate. Since non–motor symptoms develop before the onset of motor symptoms in PD, most of the PD cases are judged from the initial symptoms, however, atypical cases often encountered. Although conventional MRI do not show any abnormalities in PD, disappearance of nigrosome 1 can be confirmed by high magnetic field MRI susceptibility weighted images. Further, dopamine transporter scintigraphy (DaT–SPECT) is a sensitive for parkinsonism and iodine–123–metaiodobenzylguanidine (¹²³I–MIBG) has higher specificity of PD diagnosis myocardial scintigraphy. However, the advanced stage of PD involves dementia with overlapping Aβ and tau pathology, leading to the mixed pathology of PDD/DLB which are clinically problematic. Differentiation from DLB, AD, PSP, CBD is also enabled by brain SPECT. Progress of these diagnostic tools is improving the correct diagnosis of PD, but quite a few familial PD and atypical cases exist. In this lecture, the tips as the clinical and pathological discrimination points of PD and other parkinsonian syndromes are outlined with specific cases. Further, not only various pathological background but also trauma and inflammation of the brain are required to consider the modifying factor for the diagnosis and treatment of PD.