Postanoxia-Induced Chorea Treated with Intravenous Fentanyl

Figure 1

Direct and indirect pathways of the basal ganglia. The direct pathway, represented by the dashed line, begins in the cortex, sending a stimulatory signal to the caudate and putamen. The caudate and putamen then send inhibitory signals to the GPi which inhibit the thalamus, therefore inhibiting an inhibitor, leading to overall stimulation of movement. The indirect pathway, represented by the solid line, also begins by the cortex stimulating the caudate and putamen. The caudate and putamen then send an inhibitory signal to the GPe. The GPe inhibits the subthalamic nucleus which stimulates the GPi. Therefore, the end result of the indirect pathway is stimulation of the inhibitory GPi, leading to inhibition of movement. The substantia nigra acts on both pathways using dopamine, using D1 receptors to stimulate the direct pathway and D2 receptors to inhibit the indirect pathway. (SN, substantia nigra; GPE, globus pallidus externus; GPI, globus pallidus internus; STN, subthalamic nucleus).