Chronic pain and central changes

Acute pain is caused by injury, surgery, illness, trauma or painful medical procedures It serves as a warning of disease or a threat to the body .It generally lasts for a short period of time, and usually disappears when the underlying cause has been treated or has healed. The pain receptors are nociceptors. They are known to exist in muscle, joints, and skin. Each nociceptor has selective sensitivity to mechanical (muscle-fiber stretching), chemical (including lactic acid), and thermal stimuli. Pain is considered chronic if it lasts three months or longer .Dealing with chronic pain can be especially trying if you don't know the cause. Peripheral sensitization : increased responsiveness and reduced threshold of nociceptive neurons in the periphery to the stimulation, which usually occurs after peripheral tissue injury and inflammation. Central sensitization A hypersensitivity to stimuli from things that are not typically painful. Central sensitization is defined as an increased responsiveness of nociceptors in the central nervous system to either normal o sub-threshold afferent input Living with any type of pain, acute or chronic, can interfere with many normal aspects of everyday life.The patients with chronic pain exhibit enhanced activity in certain cortical and subcortical areas, such as higher activation of the medial PFC, cingulate cortex, amygdala, and insular lobe, and reduced activity in the pain-relief areas and altered functional connectivity (FC) in pain-associated areas. These findings are indicative of a relationship between chronic pain and broad changes in brain networks.Structural changes :Being in long term pain literally changes the structure of brain. Chronic pain reduces the volume of gray matter in our brains .Grey matter is the area of the brain which controls learning, attention, memory, thought processes, motor control and coordination.One study found that the individuals with persistent pain exhibit increased FC between the medial prefrontal cortex (mPFC) and the nucleus accumbens (NAC) at initial evaluation. After ۳ years, the structural components associated with pain, along with FC between mPFC, amygdale, and NAC, altered in persistent LBP and those who recovered from LBP. However, those who progressed to chronic pain had relatively smaller amygdala and hippocampus volumes, suggesting that these structural changes may have occurred before the onset of pain, potentially predisposing individuals to develop chronic pain. In addition, can also be important factors in the developmentcognitive and emotional responses to pain and maintenance of chronic pain. With a shift to chronic pain, brain activity, associated with chronic pain perception, shifts from areas involved in acute pain to areas participating in emotional circuits such as medial prefrontal cortex/amygdale .As a result, the perception shifts from pain-oriented to specific emotions such as fear, anxious and sadness .Problem: Patients with chronic pain do not respond to various conventional treatments, including drugs, injections with anesthetics and corticosteroids, rehabilitation CBT is a talking therapy that can help you manage your problems by changing the way you think and behave .It's most commonly used to treat anxiety and depression, but can be useful for other mental and physical health problems .Transcranial Electrical Stimulation: TMS or tDCS are a safe, non-invasive technique that uses an electromagnetic coil or electrodes to generate a magnetic field or electrical stimulation into brain.These pulses induce changes in cortical excitability at the stimulation siteeffective in improving motor and cognitive functions and reducing depressive symptoms in several disorders, including stroke, Parkinson's disease, and major depressive disorder .induces pain reducing effects in various pain conditions The mechanism of cortical stimulation for pain relief is based on the modification of neuronal excitability.TMS or tDCS induce alterations in the activity of cortical and subcorticalBrain structures that are related to pain modulation and processing, including the orbitofrontal cortices, medial thalamus, anterior cingulate, and periaqueductal gray matter .Additionally, rTMS or tDCS reduce chronic pain by triggering descending inhibitory neural pathways to act at the dorsal-horn levelStimulation frequency is associated with synaptic changes higher frequencies (> ۵ Hz) are excitatory lower frequencies (< ۱ Hz) are inhibitory When positive stimulation (anodal tDCS) is delivered, the current causes a depolarization of the resting membrane potential, which increases neuronal excitability and allows for more spontaneous cell firing. When negative stimulation (cathodal tDCS) is delivered, the current causes a hyperpolarization of the resting membranepotential. This decreases neuron excitability due to the decreased spontaneous cell firingNew approach for treatment of chronic pain: Based on both central and peripheral interventions, and not peripheral interventions alone