The spinothalamic tract carries touch, pain, and temperature information. The central tegmental tract contains ascending fibers connecting the rostral nucleus solitarius to the thalamus and cortical taste area. The lateral lemniscus carries auditory information to the auditory cortex. The medial lemniscus carries proprioceptive, vibratory, and touch-pressure sense. The medial longitudinal fasciculus is the main central connection for the oculomotor nerve and coordinates conjugate gaze. The white matter tracts pass through the entire length of the brainstem and include the medial longitudinal fasciculus, medial lemniscus, lateral lemniscus, central tegmental tract, spinothalamic tract, and rubro-olivary tract. The red nucleus, part of the extrapyramidal system, has roles in motor coordination. The substantia nigra functions in motor control and reward pathways. The dorsal tegmentum is ventral to the cerebral aqueduct and contains the nuclei of the oculomotor (III) and trochlear (IV) cranial nerves, white matter tracts, and gray matter including the substantia nigra and red nucleus. We describe brainstem development and structure with a focus on the imaging appearances of pathologic abnormalities to help the radiologist understand these conditions. Knowledge of the complex function and anatomy of this region is key to understanding the wide spectrum of disease. The brainstem also contains all of the cranial nerve nuclei other than the olfactory (I), optic (II), and part of the accessory (XI) nerves.īrainstem syndromes are usually due to vascular occlusion of branches of the posterior circulation or mass effect secondary to space-occupying lesions. It has connections to the cerebrum, basal ganglia, diencephalon, cerebellum, and spinal cord. Functions include regulation of the cardiac, respiratory, and central nervous systems including consciousness and the sleep cycle. The named parts, from cranial to caudal, comprise the midbrain (mesencephalon), pons (metencephalon), and medulla oblongata (myelencephalon). The brainstem is the most inferior and primitive part of the brain, continuous caudally with the spinal cord and rostrally with the diencephalon (thalamus, hypothalamus, epithalamus, and subthalamus) ( 1).
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