Neuropathic pain (NP) is a subtype of chronic pain syndrome defined by International Association of the Study of Pain (IASP) as a “pain caused by a lesion or disease of the somatosensory system.” Consequence of CNS or PNS lesions are activities generated in the somatosensory system without peripheral afferent stimulation. The pathophysiology of the somatosensory system is injury causing complex ectopic signaling between neuronal pathways. There are several types of antineuropathic medications that are currently utilized to treat this subtype of pain, including gabapentin, pregabalin, and duloxetine, amongst others.

Complex regional pain syndrome (CRPS) is a long-term pain condition that commonly affects the extremities and is associated with increased sensitivity to pain and touch. CRPS is classified into two types: CRPS-I and CRPS-II. The former occurs when there is no apparent nerve damage, whereas the latter is linked to known nerve damage. Psychological factors may play a role in the development of CRPS, with studies indicating that individuals with a history of depression and PTSD are at a higher risk of developing this condition. There are various treatment options available for CRPS, including physical therapy, medication, and interventional techniques such as nerve blocks and transcranial stimulation. However, larger and more comprehensive studies are needed to assess the effectiveness of these therapies. While NSAIDs have not been found to be effective in treating CRPS, sympathetic nerve blocks are commonly used but have mixed results. Finally, spinal cord stimulation (SCS) is a surgical treatment option that is recommended after conservative treatments have failed to produce significant symptom relief over several months.

Phantom limb pain (PLP) is a common source of distress and discomfort post-amputation. Up to 85% of amputees will experience PLP at some point and many cases become chronic pain conditions. While the pain has been well documented for decades, the exact pathophysiology is still unclear, and thus hindering a more accurate means of treatment. Patients with significant pain in the limb pre-amputation, lack of psychological counseling, and more proximal amputations in general seem to be more prone to pain; however, the presentation of PLP varies greatly from case to case. There are many noninvasive therapies, exercises, and medications that are recommended as first-line treatment, but the most effective and best-evidenced treatments involve electrical stimulation of peripheral nerves. Despite this lead on a promising treatment, the quality of evidence supporting or refuting any given modality is overall weak and requires much more homogenous study to truly be analyzed for efficacy.