Computed tomography and magnetic resonance imaging of the brainstem

The brainstem is a fundamental central nervous system component, essential for life. It comprises the midbrain, pons, and medulla oblongata. It is connected superiorly to the diencephalon, inferiorly to the spinal cord, and posteriorly to the cerebellum. The brainstem is pivotal in permitting transit for ascending and descending tracts, integrative functions, such as consciousness and respiratory cycle, and transmitting action potentials to cranial nerves. Lesions in this region can lead to diverse neurologic deficits. Imaging the brainstem presents challenges due to the proximity of critical structures and potential artifacts. While computed tomography and ultrasound have limitations, magnetic resonance imaging (MRI) is preferred, particularly at higher field strengths, offering superior anatomic details. The compact nature of the brainstem poses challenges in distinguishing its nuclei on MRI. Despite technical hurdles, adequate MRI protocols, including T1- and T2-weighted imaging, fluid-attenuated inversion recovery, susceptibility-weighted imaging, and diffusion-weighted imaging, enable a comprehensive evaluation. Additionally, diffusion tensor imaging with fiber tractography provides qualitative and quantitative insights into white matter tracts. This chapter reviews the normal anatomy of the brainstem through imaging, emphasizing MRI, and addresses common diseases affecting this crucial region.