This chapter reviews transcranial B‑mode sonography (TCBS) methodology and the evidence supporting its use to image the brainstem and aid diagnosis of Parkinson disease and other parkinsonisms.

As a low-cost, noninvasive imaging biomarker with reported high accuracy and interrater reliability, TCBS can support diagnosis, differential diagnosis, and patient stratification in clinical research and trials, though it provides little direct mechanistic or therapeutic insight.

Transcranial B-mode sonography (TCBS) is a well-established neuroimaging technique that enables the visualization and structural evaluation of certain brain structures. This chapter focuses on the application of TCBS and its potential use in the diagnosis of several neurologic disorders. The first part of this chapter outlines the technical requirements and describes the ultrasound method for an optimal TCBS examination in detail. The second section focuses on the existing evidence in movement disorders, with an emphasis on Parkinson disease and parkinsonism. In the third part of the chapter, the focus will be on the limitations and advantages of the TCBS. Current data indicate that TCBS is a cost-effective and user-friendly imaging technique with high accuracy and interrater reliability for diagnosing Parkinson disease. TCBS also serves as a valuable supplementary tool for distinguishing various movement disorders. Its limitations include potential difficulties with insufficient temporal bone windows in some individuals and the requirement for an experienced operator to achieve accurate results.