Place value of transcranial sonography in early diagnosis of Parkinson's disease.

Transcranial B-mode sonography (TCS) is a relatively new method which has been proven to be helpful in the diagnosis of Parkinson's disease (PD). Due to the underlying physical principles, supplementary information to other neuroimaging methods can be derived. Substantia nigra (SN) hyperechogenicity is the characteristic feature of idiopathic PD, which can help in the differentiation of atypical parkinsonian syndromes like multiple system atrophy or progressive supranuclear palsy. Besides, the quick 'look into the brain' can easily visualize an enlargement of the ventricular system, alterations of the basal ganglia like increased contents of calcium or trace metals, or a missing brain stem raphe, typically seen in depressive disorders, and can therefore give further diagnostic hints for symptomatic parkinsonian syndromes. Many studies indicate that SN hyperechogenicity constitutes a stable marker, irrespective of the disease stage. In a prospective study of patients with very first signs of yet unclear parkinsonism, a high predictive value of TCS for the diagnosis of PD could be proven. Moreover, there is accumulating evidence that SN hyperechogenicity could play a role in the premotor diagnosis of PD. In this review, the additional diagnostic value of TCS in the early diagnosis of PD as well as limitations of the method are being discussed. Copyright 2010 S. Karger AG, Basel.