Surgically Induced Neuropathic Pain

Abstract

Objective Nerve damage takes place during surgery. As a consequence, significant numbers (10–40%) of patients experience chronic neuropathic pain termed surgically induced neuropathic pain (SNPP). Background The initiating surgery and nerve damage set off a cascade of events that includes both pain and an inflammatory response, resulting in ‘peripheral’ and ‘central sensitization’, with the latter resulting from repeated barrages of neural activity from nociceptors. In affected patients these initial events produce chemical, structural and functional changes in the peripheral (PNS) and central nervous (CNS) systems. The maladaptive changes in damaged nerves lead to peripheral manifestations of the neuropathic state – allodynia, sensory loss, shooting pains etc., that can manifest long after the effects of the surgical injury have resolved. The CNS manifestations that occur are termed ‘centralization of pain’ and affect sensory, emotional and other (e.g., cognitive) systems as well as contributing to some of the manifestations of the chronic pain syndrome (e.g., depression). Conclusions Currently there are no objective measures of pain in the peri-operative period. As such intermittent pain or continuous may take place during and after surgery. New technologies including direct measures of specific brain function of nociception and new insights into preoperative evaluation of patients including genetic predisposition appear to provide initial opportunities for decreasing the burden of SNPP until treatments with high efficacy and low side effects that either prevent or treat pain are discovered.

AMPAkines Target the Nucleus Accumbens to Relieve Postoperative Pain

“…62,63 The spared nerve injury (SNI) model is typically used to model chronic neuropathic pain, but it can also be used to model persistent postoperative neuropathic pain, since the nerve injury and pain symptoms (hypersensitivity and hyperalgesia) in this model resemble the kind of injury and resulting neuropathic pain that can sometimes occur after intra-operative nerve resections. 62,63 Similar to PI, SNI has also been shown to lead to pain and depression-like behaviors in rats. 17 We have previously shown that systemic infusion of CX546 can relieve both mechanical hypersensitivity and depression-like behaviors in this pain model.…”

Research design considerations for chronic pain prevention clinical trials

“…Although CPSP is generally thought to be a result of surgery-induced nerve damage, the exact mechanisms are unknown and whether the mechanisms are similar between different surgery types is also unknown. Potential causes include peripheral and central sensitization [21,105,110,179,180]. It is important to note that in specific circumstances, pain is likely not neuropathic.…”

“…Preventive efficacy of a compound for CPSP should first be studied in surgical pain models with higher incidences of CPSP (i.e., 20%-60%), such as mastectomy, thoracotomy, amputation, and inguinal hernia repair [21,70] to decrease necessary sample sizes. Pain prevention studies using similar pharmaceutical agents in different post-operative models have had inconsistent results [27,120,121,150], suggesting that different mechanisms may be involved compared to other persistent postoperative pain states.…”

Circles of engagement: Childhood pain and parent brain

“…Here empathy is confounded by the unknown or uncertain duration of pain, the fluctuation in pain intensity and associated child distress. Indeed, with pain chronification, so-called centralization of pain (where maladaptive processes lead to alterations that confer changes in cognition, altered reward and altered saliency amongst others (Borsook et al, 2013b) takes place and may result in an ongoing state, that the longer it lasts, the more difficult it is to treat.…”