U. Walter
University of Rostock, Department of Neurology – Rostock, Germany

Transcranial B-mode sonography (TCS) is a non-invasive, low-cost, short-duration neuroimaging method that allows high-resolution imaging of deep brain structures in patients with inflammatory and degenerative brain diseases. Hyperechogenicity of the substantia nigra (SN), a TCS findings present in about 90% of patients with idiopathic Parkinson's disease (PD), is already present in presymptomatic disease stages. SN hyperechogenicity has been demonstrated to correlate with iron accumulation in a number of brain disorders but also with microglia activation.

The results of recent longitudinal studies suggest that TCS of SN may serve as a screening tool for detecting subjects at risk of later developing PD. In a large study we could show in addition that the combination of TCS with simple olfaction and motor tests already at very early disease stages discriminates PD from other parkinsonian disorders. In turn, normal SN echogenicity in combination with lenticular nucleus hyperechogenicity indicates an atypical Parkinsonian syndrome rather than PD with a specificity of more than 95%. TCS detects characteristic basal ganglia changes also in other movement disorders such as lenticular nucleus hyperechogenicity in idiopathic dystonia and Wilson's disease and caudate nucleus hyperechogenicity in Huntington's disease. Reduced echogenicity of midbrain raphe is frequent in depressive disorders and was found to correlate with responsivity to serotonin reuptake inhibitors. An elegant application of TCS is the intra- and postoperative localization of deep brain stimulation electrodes in patients with movement disorders. The detection of changes of deep brain structures on TCS in multiple sclerosis patients was found to have a predictive value for further disease progression.

Key words: deep brain stimulation, movement disorders, substania nigra, transcranial sonography.