Brain Sonography

Abstract

Transcranial B-mode sonography (TCS) is a non-invasive neuroimaging method that allows high-resolution imaging of deep brain structures in patients with degenerative brain diseases. Beside transtemporal axial and coronal imaging planes also transfrontal sagittal planes can be applied for special diagnostic purposes. Hyperechogenicity of the substantia nigra (SN), found in about 90% of patients with idiopathic Parkinson's disease (PD), is already present in presymptomatic disease stages. The results of longitudinal studies suggest that TCS of SN may serve as a screening tool for detecting subjects at risk of developing PD. Studies of our and other groups show 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 caudate nucleus hyperechogenicity in Huntington's disease. Lenticular nucleus hyperechogenicity in Wilsons disease has been proven histochemically to be caused by copper accumulation, while the same TCS finding is caused by iron accumulation in hereditary disorders with brain iron accumulation such as PKAN and MPAN. Reduced echogenicity of midbrain raphe is frequent in depressive disorders and in migraineurs. An elegant application of TCS is the intra-and postoperative localization of deep brain stimulation electrodes in patients with movement disorders. Upcoming technologies such as digitized image analysis and TCS-MRI fusion imaging will promote novel diagnostic applications of TCS.