Neuropathic pain can develop from either efferent activity (pain maintained by the sympathetic nervous system) or afferent activity cessation (deafferentation pain).
Neuropathy can develop from peripheral nerve damage or dysfunction. Here are few instances:
Mononeuropathies Single nerve ie, carpal tunnel syndrome. Radiculopathy owing to a ruptured intervertebral disc. Involve a single nerve carpal tunnel syndrome. Radiculopathy owing to a ruptured intervertebral disc involving a single nerve such as carpal tunnel syndrome or radiculopathy from a torn intervertebral disc. Single nerve, as with carpal tunnel syndrome or radiculopathy resulting from a ruptured intervertebral disc.
Plexopathies Several nerves inside a particular neural plexus. Often caused by trauma, inflammation, or nerve compression, as by a tumor. Multiple nerves inside a particular neural plexus. Often caused by trauma, inflammation, or nerve compression. Such as by a tumor of Multiple nerves inside a specific neural plexus. Commonly caused by trauma, inflammation, or nerve compression, such as a tumor. Multiple nerves inside a single neural plexus. Commonly caused by trauma, inflammation, or nerve compression, such as that produced by a tumor.
Polyneuropathies Multiple nerves, typically throughout the body; frequently caused by diverse metabolic disorders, paraproteinemias, toxic exposures to alcohol, chemotherapy, inherited predisposition, or, in rare cases, immune-mediated pathways involve several nerves, commonly across the body; often caused by various metabolic problems, paraproteinemias, toxic exposures alcohol, chemotherapy], inherited susceptibility, or, in rare cases, immune-mediated pathways
- The mechanics underlying neuropathic pain are intricate and subject to change.
- At the peripheral nociceptor and nerve level, the dorsal root ganglion is present.
- Terminal structures and nociceptive pathways of the central nervous system (CNS)
At the level of the peripheral nerve and nociceptor, injury induces inflammation, activation, and overrepresentation of cation channels. Specifically sodium channels. These modifications lower the activation threshold and heighten sensitivity to unpleasant stimuli.
In chronic conditions, the peripheral nerve continuously transmits ectopic nociceptive impulses to the central nervous system. This constant barrage of peripheral nociceptive information. Modifies receptive nociceptors (central sensitization). They are primed and interpret pain from mild stimuli (including nonpainful stimuli. As severe pain, and interpret that pain as originating from a larger region. Than it actually does. If the peripheral nociceptive input is suppressed, these changes can be reversed, at least briefly.
Central neuropathic pain syndromes
Central neuropathic pain syndromes (pain generated by malfunction of somatosensory pathways in the CNS) can result from any CNS. the lesion, but they are most typically linked with a stroke, spinal cord injury, or demyelinating plaque in multiple sclerosis.
To be referred to as central neuropathic pain, the pain must exist in the clinically affected region of the CNS lesion. Although it need not involve the entire affected region. Only when the spinothalamic tract (pinprick, temperature sensation) malfunctions can central neuropathic pain emerge.
If pinprick and temperature sensations are normal in the suspected region of central neuropathic pain. Another source of pain must be considered. Musculoskeletal discomfort is the most common source of pain in neurologically disabled patients. (eg. shoulder pain related to arm paresis after a stroke or an upper extremity overuse syndrome in wheelchair-bound patients with a spinal cord injury).
A disruption in peripheral or central afferent neural activity results in deafferentation pain. Here are few instances:
- Pain in the middle (pain after CNS injury)
- Phantom limb ailment (pain felt in the region of an amputated body part)
- Unknown mechanisms may include central neuron sensitization, decreased activation thresholds, and larger receptive fields.
The sympathetic nervous system’s hyperactivity has been connected to neuropathic pain disorders. Although sympathetic hyperactivity does not cause neuropathic pain, it can worsen its clinical characteristics and intensity.
It is caused by efferent sympathetic activity and is known as sympathetically sustained pain. Complex Regional Pain Syndrome is characterized by pain that is sustained sympathetically. Additionally, sympathetic pain may be present in various forms of neuropathic pain.
The unknown is the reason for sympathetic overactivity in certain neuropathic pain states but not others. Incorrect sympathetic-somatic nerve connections (phases), local inflammatory alterations, and spinal cord abnormalities are the most plausible explanations.
Signs and Symptoms of Neuropathic Pain
Dysesthesias (random or produced piercing pain with a lancinating component) are common, although pain can also be excruciatingly severe. Other possible feelings are hyperesthesia, hyperalgesia, allodynia (pain caused by non-noxious stimuli), and hyperpathia (a particularly unpleasant, excessive pain reaction).
Patients may hesitate to move uncomfortable body parts, leading to muscle atrophy, joint ankylosis, bone loss, and limited mobility.
Due to the sensitization and alteration of the CNS, symptoms typically. Continue after the underlying cause has been eliminated (assuming one was present).
Evaluation of Neuropathic Pain Clinical Examination
When a nerve injury is identified or suspected, the signs of neuropathic pain are present. The cause may be obvious (amputation, diabetes, or compression, for example). If this is not the case, the diagnosis is often based on a description of the symptoms. Which are neither sensitive nor specific for neuropathic pain.
In order to confirm the diagnosis and identify the damaged nerve. Further procedures, including a neurologic exam and electrophysiologic testing, are necessary. Pain alleviated by sympathetic nerve block is referred to as sympathetically maintained pain.
Rehabilitation for Neuropathic Pain
Multimodal therapy (e.g., physical methods, antidepressants, antiseizure medicines, psychotherapy methods. Neuromodulation, and occasionally surgery). The first step in treating neuropathic pain is to confirm the proper diagnosis and address curable causes. (eg, herniated disk, carpal tunnel syndrome). To desensitize areas of allodynia and prevent trophic alterations. Disuse atrophy, and joint ankylosis, mobility and physical therapy are required in addition to medication.
Psychological issues must be addressed immediately at the initiation of treatment. Anxiety and depression must be appropriately treated. Neural blocking may be useful if the discomfort persists. When first-line medications fail to alleviate functioning, patients may benefit from the comprehensive approach of a pain clinic.
Neuromodulation (stimulation of the spinal cord or peripheral nerves) is very helpful for alleviating neuropathic pain.
Several drug types are beneficial, but complete treatment is uncommon; therefore, it is essential to maintain realistic expectations. The objective of pharmacologic pain management is to alleviate neuropathic pain.
Opioid analgesics can provide some pain relief, but they are frequently less effective than treatments for acute nociceptive pain and carry the risk of addiction; side effects may restrict the analgesia’s efficacy.
Antidepressants and epileptic medicines are examples of adjuvant analgesics
It is most frequently used to treat neuropathy, and randomized trials support its efficacy (1; see table Drugs for Neuropathic Pain).
Because of this, gabapentin is one of the most commonly utilized medications. For appropriate analgesia, the dose should be greater than 600 mg orally three times daily, and many individuals require a larger quantity. The maximum recommended oral dosage is 1200 mg three times daily.
Pregabalin 100mg is identical to gabapentin, but it has more stable pharmacokinetics. Two daily dosages are just as effective as three daily dosages and result in more patient compliance. Oral use of at least 300 mg daily is advised. (eg, a starting dose of 75 mg 2 times a day, increased to 150 mg 2 times a day within 1 week). Neuropathic pain issues may require as much as 600 mg each day.
Despite the fact that the two medications have a similar mechanism of action. Some individuals who do not respond or tolerate gabapentin may respond to or tolerate pregabalin. Vice versa (binding to the alpha-2 delta ligand of the presynaptic calcium channel. Which modulates nociceptive signaling).
Tricyclic antidepressants (amitriptyline, nortriptyline, and desipramine) impede serotonin and norepinephrine reuptake as its primary mechanism of action. Standard analgesic doses (75 to 150 mg orally once daily) are insufficient to treat depression or anxiety.
Typically, anticholinergic and adrenergic adverse effects limit the optimum dose. Antidepressants containing secondary amine tricyclic amines (nortriptyline and desipramine) show fewer adverse effects than antidepressants containing tertiary amine tricyclic amines (amitriptyline and desipramine) (amitriptyline).
Pregalin 50mg appears to be beneficial for diabetic neuropathic pain, fibromyalgia, chronic musculoskeletal pain (especially low back pain), and chemotherapy-induced neuropathy. Effective doses for treating depression, anxiety, and pain are comparable.
The effects and mechanism of action of venlafaxine are comparable to those of duloxetine.
For peripheral symptoms, topical medications and a patch containing lidocaine may be beneficial.
Other treatments that may be effective include:
Spinal cord stimulation with an epidurally implanted electrode is utilized for specific types of neuropathic pain. (eg, chronic leg pain after spine surgery)
Along peripheral nerves and ganglia, electrodes are placed to treat persistent neuralgias (peripheral nerve stimulation)
In all but a handful of cases of complicated regional pain syndrome, sympathetic blocking is unsuccessful.
Neuronal obstructing or ablating (radiofrequency ablation, cryoablation, chemoneurolysis)
Skin electrical nerve stimulation (TENS)