Randomized clinical trial of deep brain stimulation for poststroke pain

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Neuropathic pain, defined as “pain initiated or caused by a primary lesion or dysfunction in the nervous system,”1 is common in the general population, with an estimated prevalence of 8% among adults enrolled in a family practice.2 It can be associated with pathology of the peripheral nervous system or the central nervous system (typically referred to as central pain). When central pain is associated with stroke, typically involving the somatosensory thalamic nuclei or the somatosensory ascending pathways, it is commonly referred to as poststroke pain syndrome (PSPS). PSPS is commonly characterized by hemiparesis associated with severe unrelenting anesthesia dolorosa and is known to be particularly refractory to pharmacological, interventional, and surgical treatment modalities.3
Treating patients with PSPS can be extraordinarily frustrating for both the patient and the physician. To date, interventional and neurostimulation‐based treatment modalities (eg, deep brain stimulation [DBS], spinal cord stimulation, and motor cortex stimulation) have focused almost exclusively on modulation of pain transmission through ascending pathways (eg, lateral spinothalamic tract).4 The primary endpoint is typically analgesia, with efficacy defined as a reduction of ≥50% in pain magnitude reported by the visual analog scale (VAS) in 50% of patients.7 Despite significant advances, the majority of patients undergoing surgical intervention for the management of medically refractory PSPS fail to experience significant long‐term benefits.6
Traditionally, neurostimulation therapies for pain attempt to interrupt or modulate the sensory‐discriminative pathways. However, our current scientific understanding of pain, described by the neuromatrix theory, indicates that the overall pain experience (and consequently disability) is determined by the integration of nociceptive inputs with the affective and cognitive spheres of pain processing.9 In this study, we departed from an analgesia‐based approach and focused on neural networks related to the control of emotion and behavior. This approach was based on the hypothesis that modulation of the affective sphere of pain would relieve pain‐related disability, with or without a reduction of pain intensity.10
To test this conceptual approach, we conducted the first federally funded prospective, double‐blind, placebo‐controlled, crossover trial of DBS for neuropathic pain. We targeted the ventral striatum/anterior limb of the internal capsule (VS/ALIC), given its well‐established role in the control of emotion and behavior11 and the previously documented safety and efficacy of VS/ALIC DBS for the treatment of obsessive–compulsive disorder (OCD) and treatment‐resistant depression (TRD).12 This trial included 10 patients with PSPS who had hemibody pain and anesthesia dolorosa secondary to a contralateral lesion.
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