​Kembara Xtra - Medicine - Neuropathic Pain

​Kembara Xtra - Medicine - Neuropathic Pain 
The term "neuropathic pain" refers to a wide range of pain syndromes and includes both peripheral and central illnesses.
 Is described as damage to the nociceptive pathway in the central or peripheral nervous system (CNS and PNS), which causes a decrease in, disappearance of, or conversely an increase in pain feeling.
The symptoms are typically severe and resistant to painkillers, burning, tingling, sharp, stabbing, shooting, and electric shock-like qualities.

 Incidence
As most research focus on a specific type of neuropathic pain, there is limited evidence regarding the overall incidence rate of neuropathic pain. 9,135 new instances of neuropathic pain out of 362,693 participants in a Dutch study conducted between 1996 and 2003 were found, translating to 8.2 new cases per 1,000 person-years (PY). According to the study, the incidence affects more women and people in their middle years annually at a rate of close to 1% of the overall population.
Prevalence
includes long-term conditions, which account for 20–25% of people with chronic pain and may affect up to 10% of the population.
 Malignancy: Up to 20% of people with cancer or cancer therapy experience neuropathic pain.
 Up to 8% of post-stroke patients
 Syringomyelia is seen in the majority of people with spinal cord injuries (60–69%).
 25% lifetime incidence of herpes zoster. 10% of people may experience chronic postherpetic neuralgia.
 Up to 50% of people with HIV experience neuropathic pain.
Diabetes: 34% will experience neuropathic discomfort, and 50% will eventually develop neuropathy.

Pathophysiology and Etiology 
Neuropathic pain is caused by a number of mechanisms, many of which are still not fully understood.
● According to one theory, injured primary afferents, including nociceptors, become extremely responsive to mechanical stimuli and may even produce impulses without external stimulation. The increased sodium channel density in the injured nerve fibers, which results in higher excitability and signal transduction, is assumed to be the reason of this increase in sensitivity and spontaneous activation without obvious stimulation.
Genetics Genetic influences on neuropathic pain are becoming more and more clear. Studies on human genetics have shown that the dorsal root ganglion's peripheral nociceptive neurons express the voltage-gated sodium channel subtypes Nav1.7 and Nav1.8, which are respectively encoded by the SCN9A and SCN10A genes, at high levels. Therapeutics that target these channels with certain genetic alterations can therefore aid in the treatment of patients.

Risk Elements 
Older age, being a woman, being physically inactive, and working manual labor are all risk factors.
HIV, Lyme disease, diabetes mellitus types I and II, multiple sclerosis, Guillain-Barré syndrome, herpes zoster, trigeminal neuralgia, cancer/chemotherapy, nutritional deficiencies (B6 and B12 deficiency), and medicine (isoniazid, ethambutol, chloroquine, paclitaxel, cisplatin, amiodarone, vincristine).

Basic Prevention 
The use of herpes zoster vaccines, which lower the risk of postherpetic neuralgia and herpes zoster infections in people over 50.
 The use of antiviral or analgesic medication in herpes zoster patients
 Preventing chronic postoperative pain in surgical patients through perioperative care. Using gabapentin and local anesthetics in combination to provide multimodal analgesia to avoid acute and ongoing pain following breast cancer surgery

Accompanying Conditions 

Suicidal ideation, depression, anxiety, sleep issues, substance misuse, cognitive impairment, and polypharmacy
DIAGNOSIS
The clinical history and the results of the physical examination serve as the foundation for the diagnosis.


History: Location, intensity (0–10), exacerbating causes, onset and duration of symptoms
 People frequently describe pain as being like an electric shock, searing, shooting, or tingling.
The severity of the symptoms increases as the day wears on.
 Numbness, weakness, diminished sensitivity to touch, pinprick, warmth, or vibration, and diminished proprioception are some examples of sensory descriptions.
Affects sexual, ambulatory, self-care, and sleep functions. Previous medical, surgical, and psychosocial history. Substance abuse, particularly alcohol.
Previous therapies: Acetaminophen or NSAIDs are typically ineffective for treating neuropathic pain. Various questionnaires have been developed as screening techniques, including: Douleur Neuropathique's four questions, the Leeds Assessment of Neuropathic Symptoms and Signs, the Neuropathic Pain Questionnaire, Pain DETECT, and the Neuropathic Pain Symptom Inventory.


clinical assessment 
Positive symptoms include hyperalgesia, which is an excessively elevated pain response to stimuli such as pressure, heat, or cold.
- Light touch, clothing, or bed linens that cause allodynia (pain from nonpainful stimulation).
Negative effects include hypoesthesia, which is an abnormally diminished sensation of touch or temperature
Gross motor examination: Weakness, exhaustion, reduced range of motion, stiffness, and muscle spasm; hypotonia, tremor, dystonia, ataxia, hypo-/hyperreflexia, and motor neglect
Sensory evaluation: Proprioception, vibration sense, light touch, and pinprick sensation may be either heightened or lowered.
- There may be sensory disruption outside of a specific nerve area.
When looking at the skin, look for changes in warmth, color, perspiration, and hair growth that point to sympathetic nervous system involvement, such as those associated with complex regional pain syndrome (CRPS).
- - Acanthosis nigricans may be a sign of diabetes; residual dermatomal scars may be an indication of a past herpes zoster infection.

Differential diagnoses include somatic symptom disorders, conversion disorders, and nociceptive pain brought on by genuine tissue damage.

Laboratory Results 

Although it confirms distribution, neurologic testing is not yet useful in deciding on a course of treatment. The following confirmatory tests are available (in descending order of invasiveness):
Sensory evaluations include touch, pinprick, pressure, cold, heat, vibration, and temporal summation. Quantitative sensory testing tests the afferent nociceptive and nonnociceptive systems using standardized mechanical and thermal stimuli. Blink reflex testing evaluates the trigeminal afferent system.
- The nonnociceptive large fiber function of the peripheral nerves is evaluated by a nerve conduction study, or electromyography.
- Laser-evoked potentials (LEP) and somatosensory-evoked potentials (SEP) are used to measure afferent fiber function.
Skin biopsy measures intraepidermal nerve fiber quantification. Corneal confocal microscopy measures corneal innervation and tiny nerve fibers.
 CT/MRI—enables specific diagnoses like herniated discs and tumor-induced nerve compression
Initial examinations (lab, imaging)
None specifically for neuropathic pain, but they can exclude or exclude a cause as a possibility Fasting glucose/HbA1C, CBC, CMP, Lyme serology, TSH, syphilis screening, serum vitamin B12, CBC, CMP, and HIV testing

Management All drugs have a limited efficacy due to the various neuropathic pain pathways, and only a small percentage of patients get a substantial benefit at tolerable levels.
Functional goals can benefit from physical and occupational therapy.

Medication The etiology of the underlying condition is typically not related to the effectiveness of systemic medication therapies.
Combination therapy is probably more efficient than increasing the dosage of a single drug.
 Thought to be resistant to acetaminophen and NSAIDs, although frequently used in the treatment of acute pain with some benefit

Initial Line
Number needed to treat (NNT) for gabapentin with calcium channel ligand type 2 is 7, which results in a considerable reduction in pain. Precautions: needs renal dosing; dosage ranges up to 3,600 mg in three separate doses; common side effects include drowsiness, vertigo, peripheral edema, and weight gain.
Pregabalin is also available as an extended-release tablet or as enacarbil; NNT = 8.Up to 600 mg in 2 doses. Precautions: renal dosage is necessary.
Sedation, wooziness, peripheral edema, and weight gain are typical adverse effects.
NNT = 4 - nortriptyline, desipramine, amitriptyline, clomipramine, and imipramine are four tricyclic antidepressants.
 Dosage: Start with 10 to 25 mg at bedtime and work your way up to 150 mg/day as tolerated by adding 10 to 25 mg every 4 to 7 days.
Cardiovascular disease, glaucoma, prostatic adenoma, seizure, and tramadol use are all precautions.
Geriatric: falls; 75 mg maximum dose.
 Typical adverse reactions include drowsiness, weight gain, anticholinergic effects, and cardiac conduction block.
Serotonin norepinephrine reuptake inhibitors (SNRIs): NNT = 6- Duloxetine Dosing: 20 mg once daily to 60 mg twice daily; effective doses range from 60 to 120 mg daily Precautions: hepatic problem, tramadol usage, hypertension
Constipation and nausea are frequent adverse effects of venlafaxine, which is often the safest treatment for neuropathic pain.
Effective doses range from 150 to 225 mg per day. Cardiovascular disease, tramadol usage, and hypertension are precautions.
 Typical adverse effects include nausea and, at higher doses, hypertension

Next Line

For localized neuropathic pain caused by diabetes or herpes, lidocaine 5% patches are just as effective as pregabalin.
- To treat the uncomfortable area, use 1 to 3 patches for 12 hours each day. - Common side effects include localized erythema, itching, and rash.
Capsaicin high-concentration patches (8%): NNT = 11 - Dosage: 1 to 4 patches to cover the painful area; 30 minutes for feet, 60 minutes for the rest of the body; avoid use on face; benefits last up to 3 months - Pain (first increase), erythema, itching, uncommon occurrences of hypertension, and increasing neuropathy are common adverse effects.
- Low-concentration capsaicin cream has no advantages.

Botulinum toxin type A: Limited evidence based on insufficient research, no increase in quality of life
Dosage: Subcutaneously administer 50–200 units to the sore area; repeat every three months.
 Common adverse reactions include soreness and infection at the injection site.
Low-quality data for cannabinoids (dronabinol and nabilone): NNT = 20 for a 50% reduction in pain; Number needed to harm (NNH) = 3 for adverse effects.
For withdrawal owing to unfavorable events, NNH = 25
Opioids, including tramadol, have no long-term benefits that have been established, and their effectiveness in treating neuropathic pain is disputed. Chronic opioid use also reduces the number and sensitivity of opioid receptors, which heightens hyperalgesia.

Referral 

If the initial treatment is ineffective, consult a pain clinic to try some alternative methods.

Furthermore Treated 
40–60% of individuals who get interventional pain management (epidural or peripheral nerve injections) will have temporary alleviation.
The optimal response to spinal cord stimulation (SCS) is constant, unchanging pain. Best evidence for leg discomfort following unsuccessful back surgeryZiconotide has shown efficacy when administered intrathecally, and transcutaneous electrical nerve stimulation is frequently utilized but only slightly effective.
In addition to conventional treatments, cognitive-behavioral and mindfulness therapies can be helpful, particularly in postherpetic neuropathy.


Surgical Techniques 
Nerve-damaging procedures have not proven beneficial and may result in more insult or injury (the treatment of terminal cancer is an exception).
 Lateral cordotomy Trigeminal nerve ganglion ablation Sympathectomy dorsal root entrance zone lesion

Alternative Therapies 
There is scant evidence that acupuncture reduces pain.

Prognosis 

Chronic pain symptoms frequently need to be managed with a variety of drugs and additional treatments. Continuous examination, patient education, and reassurance are necessary for pain management. Complete relief from discomfort is uncommon.

Complications 

Drug addiction and long-term impairment are both possibilities.