The regional anatomy around the DBS lead in the ventral intermediate nucleus of the thalamus (Vim) determines efficacy and adverse effects. Understanding the regional anatomy allows the programmer to adjust the stimulation to provide optimal benefit and the absence of adverse effects. Vim is the target of therapeutic DBS. The ventrocaudal nucleus of the thalamus (Vc) lies posterior to the Vim. Electrical stimulation of Vc can cause treatment-limiting paresthesias. The corticospinal and cortical bulbar tracts in the internal capsule lie lateral and ventral to the Vim. Electrical stimulation of the internal capsule can cause tonic muscle contractions. There are multiple nomenclatures of the subnuclei of the thalamus. Although the term ventrolateral thalamus (VL) is commonly used in the physiology literature, ventral intermediate thalamus (Vim), is used in the DBS literature. Technically, the VL refers to both regions of the thalamus that receive inputs from GPi and cerebellum, whereas Vim refers to the cerebellar-receiving area of the thalamus and is thus a subdivision of the VL and is the target of DBS for tremor-related disorders.
Distinct cortical responses evoked by electrical stimulation of the thalamic ventral intermediate nucleus and of the subthalamic nucleus
