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.

Vertebral compression fractures are characterized by a break in the vertebrae comprising the spinal column, most likely on the anterior side and most commonly occurring when the osseous matrix has been weakened. The high morbidity and mortality associated with VCFs have given rise to an estimated annual medical cost of $13.8 billion in the United States alone. Prevention includes screening at-risk individuals’ bone marrow density and augmenting individuals with decreased bone density with bisphosphonates or RANK ligand inhibitors. The management of VCFs has been heavily debated with arguments for both conservative management and invasive augmentation through vertebroplasty and kyphoplasty. Invasive management should be considered in patients with uncontrolled pain, significant vertebral misalignment, and height deformities.

Over-the-counter analgesics, including NSAIDs and acetaminophen, are often the first-line medication for nonspecific low back pain (LBP). Current guidelines recommend their use as the initial treatment for LBP. In addition to these medications, antidepressants, muscle relaxants, and opioids can also be effective treatments for chronic LBP. Acetaminophen, which is also known as paracetamol internationally, is commonly used for its pain-relieving and fever-reducing properties. Although the mechanism of action is not fully elucidated, acetaminophen is known to inhibit cyclooxygenase (COX-1 and COX-2), resulting in inhibition of prostaglandin synthesis. It works by lowering body temperature during fever and inhibiting the activity of COX-3, resulting in analgesic and antipyretic effects. Para-acetyl-aminophenol (acetaminophen) acts as a reducing agent and inactivates the oxidized cyclooxygenase enzyme. Nonsteroidal anti-inflammatory drugs (NSAIDs), on the other hand, are more effective for LBP due to their superior anti-inflammatory effects. They are often compared to acetaminophen or used in combination for LBP treatment.

Chronic abdominal pain (CAP) is a constant or recurrent pain that lasts for more than three months. Abdominal pain is the most common GI symptom, and it is a leading cause for inpatient and outpatient visits. International prevalence is between 22% and 25%, with more women reporting abdominal pain than men (24% versus 17%). Many diseases can cause CAP. Treatments include celiac plexus neurolysis, celiac plexus blocking agent, various pharmacologic treatment, spinal cord stimulation, and lifestyle modifications.

Chronic post-stroke pain (CPSP), Dejerine Roussy syndrome, is a specific injury resulting from usually ischemic stroke. Diagnosing and discovering direct mechanisms are still works in process. The syndrome is also hard to differentiate among other similar ones due to the varying symptomatic responses in individuals. Many different therapy processes and management systems are being studied to find an efficient and safe way to reduce the pain in individuals with CPSP. Seen in the treatments and management section, some techniques are invasive, while others are not. Transcranial stimulation is invasive. It leads to many other complications that come with surgical procedures. Other methods are not as invasive and have some existing evidence of reducing pain. Many of the treatments and management of CPSP still need more evidence to fully figure out their mechanisms of action and the consistent effects of the treatments. The different methods appear to have promising results and future research can help to uncover that potential.

Multiple sclerosis (MS) is an autoimmune disorder of the central nervous system, causing inflammation with oligodendrocyte death and myelin sheath destruction. Classical symptoms of MS are fatigue, paresthesia, motor deficits, cognitive dysfunction, visual disturbances (due to optic neuritis), spasticity, depression, gait disturbance, and pain. To make a formal diagnosis of MS, the 2017 McDonald criteria is used. Pain in MS can present itself as headache, extremity pain, back pain, neuropathic pain, or more specifically, trigeminal neuralgia. Pain in MS can be severe and chronic enough to cause disability and decreased quality of life. The prevalence of neuropathic pain in MS can be as high as 86% and it can manifest itself as back pain, headache, trigeminal neuralgia, or extremity pain. When present, it is associated with MS, which tends to be more severe, with a higher degree of disability. Early treatment of these pains leads to better outcomes of MS itself. Conventional methods to treat pain in these patients produce only a 50% reduction in symptomatology. Some unconventional treatment modalities that have benefited patients are antidepressants, anticonvulsants, cannabinoids, low-dose naltrexone, and spinal stimulation.

Thoracic outlet syndrome is a collection of conditions that lead to the compression of the nerves and blood vessels in the thoracic outlet area. Symptoms such as pain, numbness, weakness, and discoloration may occur depending on the specific structures affected. There is currently no agreed-upon diagnostic criteria, but a detailed patient history, physical examination, and appropriate imaging tests can help with diagnosis. The first-line treatment for thoracic outlet syndrome usually involves conservative measures like physical therapy, lifestyle changes, medications such as NSAIDs and injections like botulinum toxin A, steroids, and local anesthetics. If conservative treatments fail, surgical decompression may be considered. This chapter aims to provide a review of the epidemiology, causes, anatomy, symptoms, diagnosis, and treatment of thoracic outlet syndrome.

Ibuprofen and naproxen are nonsteroidal anti-inflammatory drugs (NSAIDs) that work by inhibiting cyclooxygenase (COX) 1 and 2, enzymes involved in the synthesis of prostaglandins that contribute to pain, inflammation, and fever. Therefore, cyclooxygenase modulation contributes to the anti- inflammatory and analgesic qualities of ibuprofen and naproxen. While NSAIDs have been shown to be effective in the treatment of chronic low back pain, they can also have adverse effects on the gastrointestinal, renal, and coagulation systems, including gastric pain, vomiting, bleeding, gastric ulcers, acute renal failure, interstitial nephritis, and nephritic syndrome. Long-term use of NSAIDs increases the risk of such side effects. While short-term use is considered relatively safe, the evidence for the long-term efficacy of NSAIDs for chronic low back pain is limited, and the ACP recommends them as a first-line pharmacological agent with caution. The use of NSAIDs, especially over a prolonged time, is also not without risk. Long term use predisposes patients to considerable side effects.

Pain is quite common in patients with cancer, especially those with metastaticdisease. Oncologic pain implications: decreased quality of life, can be an indicator of the progression of a tumor, and psychosocial effects such as anxiety and depression. Cancer pain is divided into acute form and chronic form. Advances have been made in both oncology and pain management. The application of pain management into clinical oncology is still a work in progress. Pain management that is sufficient and consistent is difficult in cancer patients. Cancer pain affects a large portion of those with cancerous disease processes. Metastatic disease tends to be associated with more pain. Pain can come from the cancer itself or from the treatment. More work is needed to standardize the evaluation and treatment of cancer pain. Further work is needed to take into account each individual’s unique circumstance.

Although anesthesiology and endocrinology are two distinct branches of medicine, some recent breakthrough treatments have brought together both medical specialties, particularly those concerned with surgical sciences and critical care. Related to the use of various traditional surgical techniques, the lack of newer and safer drugs, the lack of monitoring tools, and the scarcity of critical care services in the past, managing patients with various endocrine disorders has always been perceived as being more difficult by practicing anesthesiologists.