Transcranial sonography of the cerebral parenchyma: Update on clinically relevant applications

SummaryTranscranial B-mode sonography (TCS) is a neuroimaging technique that displays the brain parenchyma and the intracranial ventricular system through the intact skull. Sophisticated TCS systems can currently achieve a higher image resolution of echogenic deep brain structures than MRI under clinical conditions. The different imaging principle of TCS allows visualization of characteristic changes in several neurodegenerative diseases that can hardly be visualized with other imaging methods, such as substantia nigra hyperechogenicity in Parkinson's disease (PD), and lenticular nucleus hyperechogenicity in atypical Parkinsonian syndromes. The intracranial ventricular system and a midline shift due to space-occupying brain lesions (e.g., intracerebral hematomas) are reliably assessed with TCS. The present paper reviews recent studies on diagnostic TCS applications that, as a result, can be recommended for routine use in clinical practice. These applications include the bedside monitoring of space-occupying lesions in acute stroke patients, the early and differential diagnosis of PD, and the postoperative position control of deep brain stimulation electrodes. Novel technologies such as in-time fusion of TCS with MRI scans, automated detection of intracranial target structures, and improved 3D-image analysis promise an even wider application of TCS in the coming years.