Another kind of pain that you will see frequently is called neuropathic pain. Neuropathic pain is caused by a lesion or disease of the somatosensory system. It can affect up to 10% of the population and can arise from many different etiologies. This can be centralized versus peripheral versus a mixed. Some descriptions of neuropathic pain can include burning, electric, sharp, stabbing, tingling, or crawling. And causes of this can be from nerve pressure or damage to the afferent sensory pathways. When evaluating a patient with neuropathic pain, the history and the neuroexamination is very important. Most patients will have pain for sure, but some might also have sensory deficits. Location of pain and other symptoms are very important also. Regarding a neuroexam, you can focus on sensory strength and deep tendon reflexes. Also, you can test the vibration, proprioception, light touch, and pinprick. Some abnormal sensations with neuropathic pain are paresthesias or tingling, dysesthesias or unpleasant tingling, hyperpathia, allodynia, hyperalgesia, or also spontaneous pain. We included some of these definitions in our very first lecture if you need to review those further. Neuropathic pain usually stems from either centralized or peripheral neuropathic pain. In centralized, you can see centralized neuropathic pain in spinal cord injury, central post-stroke pain, also multiple sclerosis. In peripheral neuropathic pain, you can see this in CRPS, diabetic peripheral neuropathy, postherpetic neuralgia, radiculitis, or phantom limb pain. Mentioned on the last slide, CRPS, or chronic regional pain syndrome, it is a syndrome characterized by chronic pain, tenderness, and vasomotor instability, which is very important, usually involved with a distal extremity. There's type 1 and type 2. Type 1 was previously known as reflex sympathetic dystrophy, and it does not have a demonstrable nerve lesion. Type 2 is also called causalgia. That one you can remember that is caused by a nerve damage or a nerve injury. The International Association for the Study of Pain developed a diagnostic criteria for CRPS, which is the following. The presence of an initiating noxious event or a cause for immobilization, continuing pain, or hyperalgesia that is disproportionate to any inciting event in severity, evidence of some time of edema, changes in skin blood flow, or abnormal pseudomotor activity in the region of pain, and exclusion of conditions that would otherwise account for the degree of pain and dysfunction. The distinction between CRPS type 1 and type 2 is based off findings on EMG and nerve conduction study. CRPS is a descriptive term for a group of disorders that may develop after trauma affecting the limbs, with or without an obvious nerve lesion. It may develop after visceral diseases or CNS lesions, or rarely without any other event that occurs. Some features of CRPS can include pain, sensory abnormalities, abnormal blood flow and sweating, abnormalities in the motor system, and changes in structure of both superficial and deep tissues. Not all these components need to be present, though, for CRPS to be present. Some associated signs and symptoms of CRPS can include atrophy of hair, nails, and other soft tissues, alterations of hair growth, loss of joint mobility, impairment of motor function, including weakness, tremor, and dystonia, and sympathetically mediated pain. CRPS staging has no clinical value, but historically it is usually classified into three different stages, acute or hyperemic, dystrophic or ischemic, and atrophic. Currently, there's no gold standard definitive diagnostic test for CRPS. We do try to use x-rays, triple phase bone scans, EMGs, and sympathetic nerve blocks, but most times none of these are a good diagnostic test. Some physicians can try sympathetic blockade for trying to diagnose CRPS. This can help determine whether their pain is sympathetically mediated. Neither establishes nor refutes the diagnosis of CRPS by performing the sympathetic block. It is used to guide treatment, and sometimes when it works, a physician can repeat the block if necessary. When evaluating the goals for a patient and with the patient, it should be discussed with them. The goals of the treatment for CRPS can sometimes be pain control and physical restoration. By incorporating physical therapy and early mobility, that is the main course of treatment. Some medications that have seen beneficial in CRPS can be antidepressants, anticonvulsants, opioids, and sometimes corticosteroids in the acute stages to help with the inflammatory response. Again, like we said earlier, you can try an interventional sympathetic block, and finally a neurostimulation if all those fail. Another very common neuropathy pain disorder is painful peripheral neuropathies. This can come in many different shapes and sizes and from many different etiologies. One of the most common one is a metabolic disorder you'll see in diabetic patients. Some can have nutritional deficiencies, which can lead to a peripheral neuropathy. You also have toxin exposures commonly seen in chemotherapeutic agents, genetic disorders, infectious and inflammatory disorders such as HIV and herpes zoster. And finally, you can also have this with idiopathic small-fiber neuropathy. In regards to treatment for painful peripheral neuropathies, we usually try to tackle the underlying cause of the neuropathy, such as for diabetes. We can focus on working on their blood sugars. Otherwise, we can address it with medications, which we'll discuss in the pharmacologic lecture. Some interventional treatments include sympathetic nerve blocks, neurolytic sympathetic blocks, spinal cord stimulators, and finally deep brain stimulation. And some less commonly used treatments are transcutaneous electrical nerve stimulation and repetitive transcranial magnetic stimulation.

Neuropathic pain

CRPS

diabetic neuropathy

postherpetic neuralgia

spinal cord stimulators