Early diagnosis of Parkinson's disease.

The accuracy of the clinical diagnosis of Parkinson's disease (PD) is still limited. Especially in the early stages, when cardinal symptoms are not conclusive, diagnosis can be delayed as structural neuroimaging methods such as CCT or MRI do not provide characteristic features that allow the diagnosis of this chronic neurodegenerative disorder. Functional neuroimaging using PET and SPECT techniques is helpful in patients with first signs of parkinsonism, but expensive and not broadly available. In this scenario, transcranial sonography (TCS) has proven to be helpful. Up to 90% of PD patients show hyperechogenicity of the substantia nigra (SN) on TCS. Already in the early stages of PD this echofeature is visible, allowing the differentiation of very mildly affected patients with idiopathic PD from healthy persons and from patients with atypical parkinsonism with high sensitivity and specificity. Additionally, specific ultrasound features for some forms of secondary parkinsonism can be detected by TCS, helping in the early identification, for example, of patients with Wilson's disease. Therefore, especially in the early diagnosis, TCS can be recommended as a supplementary tool to facilitate the diagnostic classification of patients with first signs of parkinsonism.