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      Systematic Review of Central Post Stroke Pain : What Is Happening in the Central Nervous System?

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          Abstract

          Central poststroke pain (CPSP) is one of the most common central neuropathic pain syndromes seen after stroke. It is mainly related with vascular damage at certain brain territory and pain related to corresponding body areas. In the past, it was described as one of the definitive symptoms of thalamic lesion. However, recent findings suggest that it is not only seen after thalamic lesions but also seen after vascular lesions in any part of the central nervous system. Although there are certain hypotheses to explain physiopathologic mechanisms of CPSP, further evidence is needed. The majority of the cases are intractable and unresponsive to analgesic treatment. Electrical stimulation such as deep brain stimulation and repetitive transcranial magnetic stimulation seems to be effective in certain cases. In this systematic review, recent advancements related to CPSP mechanisms have been evaluated. Further investigations are needed in order to reveal the mystery of the pathophysiologic mechanisms of CPSP.

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          Most cited references59

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          When does acute pain become chronic?

          The transition from acute to chronic pain appears to occur in discrete pathophysiological and histopathological steps. Stimuli initiating a nociceptive response vary, but receptors and endogenous defence mechanisms in the periphery interact in a similar manner regardless of the insult. Chemical, mechanical, and thermal receptors, along with leucocytes and macrophages, determine the intensity, location, and duration of noxious events. Noxious stimuli are transduced to the dorsal horn of the spinal cord, where amino acid and peptide transmitters activate second-order neurones. Spinal neurones then transmit signals to the brain. The resultant actions by the individual involve sensory-discriminative, motivational-affective, and modulatory processes in an attempt to limit or stop the painful process. Under normal conditions, noxious stimuli diminish as healing progresses and pain sensation lessens until minimal or no pain is detected. Persistent, intense pain, however, activates secondary mechanisms both at the periphery and within the central nervous system that cause allodynia, hyperalgesia, and hyperpathia that can diminish normal functioning. These changes begin in the periphery with upregulation of cyclo-oxygenase-2 and interleukin-1β-sensitizing first-order neurones, which eventually sensitize second-order spinal neurones by activating N-methyl-d-aspartic acid channels and signalling microglia to alter neuronal cytoarchitecture. Throughout these processes, prostaglandins, endocannabinoids, ion-specific channels, and scavenger cells all play a key role in the transformation of acute to chronic pain. A better understanding of the interplay among these substances will assist in the development of agents designed to ameliorate or reverse chronic pain.
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            Phantom limbs and the concept of a neuromatrix.

            The phenomenon of a phantom limb is a common experience after a limb has been amputated or its sensory roots have been destroyed. A complete break of the spinal cord also often leads to a phantom body below the level of the break. Furthermore, a phantom of the breast, the penis, or of other innervated body parts is reported after surgical removal of the structure. A substantial number of children who are born without a limb feel a phantom of the missing part, suggesting that the neural network, or 'neuromatrix', that subserves body sensation has a genetically determined substrate that is modified by sensory experience.
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              Electrical stimulation of motor cortex for pain control: a combined PET-scan and electrophysiological study.

              Although electrical stimulation of the precentral gyrus (MCS) is emerging as a promising technique for pain control, its mechanisms of action remain obscure, and its application largely empirical. Using positron emission tomography (PET) we studied regional changes in cerebral flood flow (rCBF) in 10 patients undergoing motor cortex stimulation for pain control, seven of whom also underwent somatosensory evoked potentials and nociceptive spinal reflex recordings. The most significant MCS-related increase in rCBF concerned the ventral-lateral thalamus, probably reflecting cortico-thalamic connections from motor areas. CBF increases were also observed in medial thalamus, anterior cingulate/orbitofrontal cortex, anterior insula and upper brainstem; conversely, no significant CBF changes appeared in motor areas beneath the stimulating electrode. Somatosensory evoked potentials from SI remained stable during MCS, and no rCBF changes were observed in somatosensory cortex during the procedure. Our results suggest that descending axons, rather than apical dendrites, are primarily activated by MCS, and highlight the thalamus as the key structure mediating functional MCS effects. A model of MCS action is proposed, whereby activation of thalamic nuclei directly connected with motor and premotor cortices would entail a cascade of synaptic events in pain-related structures receiving afferents from these nuclei, including the medial thalamus, anterior cingulate and upper brainstem. MCS could influence the affective-emotional component of chronic pain by way of cingulate/orbitofrontal activation, and lead to descending inhibition of pain impulses by activation of the brainstem, also suggested by attenuation of spinal flexion reflexes. In contrast, the hypothesis of somatosensory cortex activation by MCS could not be confirmed by our results.
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                Author and article information

                Journal
                American Journal of Physical Medicine & Rehabilitation
                American Journal of Physical Medicine & Rehabilitation
                Ovid Technologies (Wolters Kluwer Health)
                0894-9115
                2016
                August 2016
                : 95
                : 8
                : 618-627
                Article
                10.1097/PHM.0000000000000542
                27175563
                e2cbcf94-ae28-4ce7-a499-9cd0876dc514
                © 2016
                History

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