Peripheral neuropathic pain is often described as "burning", "tingling", "electrical", "stabbing", or "pins and needles". Causes
Pathophysiology
Under persistent activation, the transmission of pain signals to the dorsal horn may produce a pain wind-up phenomenon. This triggers changes that lower the threshold for pain signals to be transmitted. In addition, it may cause nonnociceptive nerve fibers to respond to, generate, and transmit pain signals. The type of nerve fibers that are believed to generate the pain signals are the C-fibers, since they have a slow conductivity and give rise to a painful sensation that persists over a long time. In chronic pain, this process is difficult to reverse or stop once established. In some cases, chronic pain can be caused by genetic factors which interfere with neuronal differentiation, leading to a permanently lowered threshold for pain.Chronic pain of different causes has been characterized as a disease that affects brain structure and function. MRI studies have shown abnormal anatomical and functional connectivity, even during rest involving areas related to the processing of pain. Also, persistent pain has been shown to cause grey matter loss, which is reversible once the pain has resolved.These structural changes can be explained by neuroplasticity. In the case of chronic pain, the somatotopic representation of the body is inappropriately reorganized following peripheral and central sensitization. This can cause allodynia or hyperalgesia. In individuals with chronic pain, EEGs showed altered brain activity, suggesting pain-induced neuroplastic changes.
People with non-cancer pain who have not been helped by non-opioid medicines might be recommended to try opioids if there is no history of substance use disorder and no current mental illness.People with chronic pain tend to have higher rates of depression and although the exact connection between the comorbidities is unclear, a 2017 study on neuroplasticity found that "injury sensory pathways of body pains have been shown to share the same brain regions involved in mood management." Chronic pain can contribute to decreased physical activity due to fear of making the pain worse. Pain intensity, pain control, and resilience to pain can be influenced by different levels and types of social support that a person with chronic pain receives, and are also influenced by the persons socioeconomic status. One approach to predicting a persons experience of chronic pain is the biopsychosocial model, according to which an individuals experience of chronic pain may be affected by a complex mixture of their biology, psychology, and their social environment. Classification
The International Association for the Study of Pain defines chronic pain as pain with no biological value, that persists past normal tissue healing. The DSM-5 recognizes one chronic pain disorder, somatic symptom disorders. The criteria include pain lasting longer than six months.The International Classification of Disease, Eleventh Revision (ICD-11) suggests seven categories for chronic pain. Chronic primary pain: defined by 3 months of persistent pain in one or more regions of the body that is unexplainable by another pain condition.