It is indeed difficult task when it comes to differentiating between pain type, that is, whether it is emerging from neuronal component (Neuropathic pain) or it is simply a result of harmful stimuli (Nociceptive pain). This post will help understand and differentiate the Neuropathic and Nociceptive pain.
Neuropathic pain occurs when there is damage to nerves of Peripheral nervous system or Central nervous system. As a result, they start eliciting pain which is sometimes hard to differentiate from noxious pain. Sodium channels are increased at the site of neural injury. This damage can occur widely from infections of inured area, diabetic neuropathy, and some surgeries.
Damaged nerves, which carry sensations, even including the nociceptors (pain carrying nerves), become highly sensitive to mechanical stimulus, and therefore, may produce pain through sensory pathway even in the absence of any mechanical stimulus. This results in hyperactivity of Central as well as Peripheral nervous system and thereby may produce continuous pain.
The skin area suffers sensory loss, however, even the mildest of some physical stimulus may produce extreme pain. This is also referred to as Hyperpathia. It can also occur with some movements of the body, termed Allodynia.
The Neuropathic pain is more precisely shooting type of pain, and felt as burning, tingling or electric shock like or it can be dull and aching. The pain, as experience by the patient, may be of continuous nature, or may be intermittent with exaggerated episodes to stimulus. The pain is pathological in nature.
Post-herpetic neuralgia, Complex regional pain syndrome (CRPS type 2), Diabetic neuropathy, HIV, Trigeminal neuralgia, etc. are some of the most interesting pain examples of neuropathic pain.
Analgesics often fail to relieve neuropathic pain, whereas Tricyclic antidepressants, Topical lidocaine, Serotonin-norepinephrine Reuptake Inhibitors (SNRIS), Calcium channel ligands and Tramadol are widely used as per management plans of the patient.
It occurs due to noxious stimuli (physically harmful) such as heat, cold, mechanical stress, ph changes, etc. which tend to electrically stimulate primary afferent nociceptors (pain receptors). Most body is innervated by A-delta and C unmyelinated fibers and some by A-Beta afferent fibers.
Primary afferent fibers or primary sensory afferents in the peripheral nerves carry impulses from potentially tissue-damaging stimuli (noxious) to produce pain sensations. These are electrically stimulated upon noxious stimuli, otherwise their normal activity doesn’t produce pain. Primary afferent fibers are A-Beta, A-Delta and C unmyelinated. They carry impulses through pain pathway to spinal cord, then brain for further processing.
The pain has high threshold, and variable descriptions account for nociceptive pain. Pain intensity decreases over time if no inflammation follows. Mechanical allodynia is uncommon and pain is protective in nature.
Sports injuries, Arthritis, Mechanical trauma, Post-operative, etc. pain are usual examples of nociceptive pain.
NSAIDs and Aspirin are common for acute pain while opioids for chronic pain. Medication may be variable on intensity of pain and choice of doctor. Tricyclic antidepressants, anti-convulsants and local anesthetics are generally ineffective.