Int Rev Neurobiol
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Neuromodulation, specifically spinal cord stimulation (SCS), relieves pain and improves organ function. This chapter discusses the limited information presently available about the underlying mechanisms that explain the beneficial effects of treating patients with SCS. ⋯ This chapter presents the infant stage of studies that attempt to explain the mechanisms which come into play for treating neuropathic pain, ischemic pain in peripheral vascular disease, and diseases of the visceral organs, specifically the gastrointestinal tract and the heart. The basic science studies will demonstrate how SCS acts on various pain syndromes and diseases via multiple pathways in the central nervous system as well as in somatic structures and visceral organs.
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We review the data concerning the neurophysiology of deep brain stimulation (DBS) in humans, especially in reference to Parkinson's disease. The electric field generated by DBS interacts with the brain in complex ways, and several variables could influence the DBS-induced biophysical and clinical effects. The neurophysiology of DBS comprises the DBS-induced effects per se as well as neurophysiological studies designed to record electrical activity directly from the basal ganglia (single-unit or local field potential) through the electrodes implanted for DBS. ⋯ DBS-induced effects at system level can be studied through evoked potentials, autonomic tests, spinal cord segmental system, motor cortical and brainstem excitability, gait, and decision-making tasks. All these variables are influenced by DBS, suggesting also distant effects on nonmotor structures of the brain. Last, advances in understanding the neurophysiological mechanisms underlying DBS led researchers to develop a new adaptive DBS technology designed to adapt stimulation settings to the individual patient's clinical condition through a closed-loop system controlled by signals from the basal ganglia.
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Functional neurosurgical procedures used to treat the debilitating motor symptoms of Parkinson's disease and that target small subcortical structures have typically relied on semi-qualitative manual approaches that rely upon the establishing qualitative between volumetric imaging data and print atlases. This chapter reviews many new high -precision and -accuracy techniques that can be used for the full automated localization of these targets. These techniques rely on the a priori development of neuroanatomical atlases derived from magnetic resonance imaging data, high-resolution identification of subcortical structures from histology, and spatially localized data bases of intra-operative recordings and successful surgical outcomes. Other novel structural and functional MRI techniques that allow for the direct visualization of thalamic sub nuclei are also reviewed.