Neuropathic pain can be caused by efferent activity (pain that is kept going by the sympathetic nervous system) or by stopping afferent activity (deafferentation pain). Pain that comes from peripheral nerve damage or malfunction can be cause by neuropathic pain. The ways neuropathy causes pain is complicate and change over time.
At the level of the nerves and pain receptors in the periphery, The dorsal root ganglion is where it is. The central nervous system has pain pathways and ending structures (CNS). At the level of the peripheral nerve and nociceptor, an injury causes inflammation and the activation and over-representation of cation channels, especially sodium channels.
These changes make the activation threshold lower and the response to painful stimuli stronger. In chronic states, the peripheral nerve continuously sends ectopic pain signals to the CNS. This constant stream of pain signals from the periphery changes the way receptive nociceptors work (central sensitization).
They are primed to think that small stimuli, even ones that don’t hurt, hurt a lot. They also think that the pain is coming from a larger area than it actually does. If the pain signals from the periphery stop coming in, these changes can be undone, at least temporarily.
Central neuropathic pain syndromes, which are pain cause by problems with somatosensory pathways in the CNS, can cause by any CNS lesion, but they are most often cause by a stroke, a spinal cord injury, or a demyelinating plaque from multiple sclerosis.
The pain must be in the area that is clinically affect
Central neuropathic pain does not have to affect the whole area where the CNS lesion is for it to consider central neuropathic pain. Central neuropathic pain only happens when the spinothalamic tract (which is responsible for feeling pinpricks and temperatures) doesn’t work right.
If pinprick and temperature feelings in the area where the pain is thought to be coming from central neuropathic pain are normal, the pain could be coming from somewhere else. Most pain in people with neurological problems comes from the muscles and bones.
Pain from deafferentation is cause by a disruption in the activity of central or peripheral afferent nerves. Here are some examples: Neuralgia postherpetic, Central pain (pain after CNS injury)
Phantom limb discomfort (pain felt in the region of an amputated body part). The exact mechanisms aren’t known, but they may involve central neuron sensitization, lower activation thresholds, and an increase in the size of the receptive field.
Overactivity of the sympathetic nervous system is sometimes link to pain syndromes cause by nerve damage. Even though sympathetic overactivity doesn’t cause neuropathic pain, it can make the symptoms and severity of the pain worse.
The pain that happens because of this is call sympathetically maintain pain, and it depends on efferent sympathetic activity. Pain that is kept going by sympathetic nerves is a sign of Complex Regional Pain Syndrome.
There may also be a sympathetic part to other kinds of neuropathic pain. It is not known why some people with neuropathic pain have overactive sympathetic nerves but not others. Most likely, the causes are abnormal connections between sympathetic and somatic nerves (phases), changes in inflammation in the area, and changes in the spinal cord.
Signs and symptoms of nerve pain
Dysesthesias, which cause random or trigger burning pain that often stings, are common, but pain can also be deep and aching. There may also be other feelings, such as hyperesthesia, hyperalgesia, allodynia (pain caused by something that isn’t harmful), and hyperpathia (a very unpleasant, exaggerate pain response).
Patients may not want to move the painful part of their body, which can lead to muscle loss, stiffening of the joints, bone loss, and limited mobility.
Because the CNS has been made sensitive and changed, symptoms usually last even after the main cause has been fixing. How to Diagnose Neuropathic Pain
Testing in the clinic, When a nerve injury is known or thought to have happen, the usual signs of neuropathic pain show up. The cause may be clear, such as amputation, diabetes, or pressure. If this is not the case, the diagnosis is often made based on a description of the symptoms. However, these descriptions, like “burning,” are neither sensitive nor specific for neuropathic pain.
So, more tests, like a neurologic exam and electrophysiology studies, are needed to confirm the diagnosis and figure out which nerve is hurt. A sympathetic nerve block can help with the pain that is kept going by the sympathetic nervous system.
How to Treat Neuropathic Pain
Multimodal treatment (eg, physical methods, antidepressants, antiseizure drugs, psychotherapeutic methods, neuromodulation, and sometimes surgery)
The first step in treating neuropathic pain is to make sure the correct diagnosis has been made and to deal with treatable causes. Mobilization and physical therapy, along with drugs, is need to make areas of allodynia less painful and stop trophic changes, disuse atrophy, and joint ankylosis from happening.
From the start of treatment, psychologists must taken into account. Anxiety and depression need to treat in the right way. If the pain doesn’t go away, neural blockade may help. When first-line treatments don’t help, a pain clinic may be able to help because it takes a more comprehensive approach. Neuromodulation, which involves stimulating the spinal cord or nerves near the skin, is a good way to treat neuropathic pain.
Several types of drugs can help (see the table Drugs for Neuropathic Pain), but it is unlikely that all of the pain will go away, so it is important to have realistic expectations. The goal of using drugs to treat pain is to make neuropathic pain less crippling.
MEDICINES FOR NEURO PAIN IN A TABLE
Opioid painkillers can help a little, but they don’t work as well as they do for acute nociceptive pain and they can make you dependent on them. They may also have side effects that stop them from working as well as they should.
Pregabalin 50mg is like gabapentin, but it has more stable pharmacokinetics. Taking two doses a day is just as effective as taking three doses a day, which makes it easier to take the medicine as prescribe. The goal dose is at least 300 mg per day by mouth (. Neuropathic pain syndromes may need up to 600 mg per day.
Even though the two drugs work in a similar way, some people who can’t take or don’t respond well to gabapentin can take or handle pregabalin 75 mg, and vice versa (binding to the alpha-2 delta ligand of the presynaptic calcium channel, which modulates nociceptive signaling).
Adjuvant analgesics, like antidepressants and seizure medicines, are most often use to treat neuropathic pain, and data from randomize trials shows that they work (1; see table Drugs for Neuropathic Pain).
Gabapentin is one of the medicines that is most often use for this. For pain relief to work, you need to take more than 600 mg three times a day, and many patients need a higher dose. The most you should take is 1200 mg by mouth three times a day.
