Neuropathic Pain: Characteristics, Causes And Treatment

Pain is a defense mechanism that alerts us to real or potential harm. However, when the pain is prolonged in time it becomes cronic or , becoming a disease itself. Chronic pain affects between 19% and 31% of the general population; of this percentage, it is estimated that 20% is of neuropathic origin.

Neuropathic pain occurs due to an injury or alteration of the structure or function of the central or peripheral nervous system. This causes a painful experience even when there is no external threat, unlike nociceptive pain.

What is neuropathic pain like?

Neuropathic pain occurs in a very varied way among people who suffer from it, ranging from mild to extremely severe pain. The pain appears some time after the injury to the nervous system and rarely disappears spontaneously.

Although all patients remit pain, the sensations can be radically different between people who suffer from the same disease or vice versa. This variety depends on causal, hereditary and environmental factors. However, neuropathic pain includes both negative and positive symptoms.

Negative symptoms, such as loss of sensitivity to painful stimuli, to temperature or in general, are usually the first indicators. On the other hand, positive symptoms, which are the result of nerve damage, can be spontaneous or evoked.

Among the symptoms spontaneous include:

• Paresthesias : abnormal and not unpleasant sensations, such as tingling.
• Dysesthesias : abnormal and unpleasant sensations.
• Spontaneous pain : stabbing, intermittent, or sharp.

Regarding the evoked symptoms, it can take place:

• Allodynia : painful perception of a non-painful stimulus, such as heat or pressure.
• Hyperalgesia : faced with a painful stimulus, an extremely painful response occurs.
• Hyperpathy : a delayed or explosive response to a painful stimulus.

In addition to these symptoms, it is common for people who suffer from neuropathic pain to develop sleep disorders and psychological disturbances due to the pain they suffer.

What are your causes?

As mentioned above, neuropathic pain is due to an injury to the pathways that transmit pain information, due to a previous illness or injury.

Therefore, the causes are so diverse that they are usually classified into four groups according to their location or anatomical distribution:

• Asymmetric focal or multifocal lesions of the peripheral nervous system . Among them, post-traumatic and postoperative neuropathies, phantom limb syndrome, post-herpetic neuropathy, HIV, etc.
• Generalized lesions of the peripheral nervous system.  Diabetic, toxic, medicinal, post-infectious or immunological neuropathy, among others.
• Central nervous system injuries. Cardiovascular accidents, head injuries, multiple sclerosis, tumors, etc.
• Complex neuropathic disorders (without obvious injury). Complex regional pain syndromes types I and II.

In a situation of non-chronic pain, the injured tissues become inflamed, causing a temporary sensitization of the area that allows the tissues to heal. However, when pain and sensitization persist, receptive neurons will begin to act in a non-adaptive way. This will cause certain stimuli to cause pain that they did not previously cause or that is perceived more intensely.

Treatments for neuropathic pain

To find the right treatment, a good diagnosis is essential. It is also essential to determine if there are other pathologies that are also causing pain. 

Since neuropathic pain has very varied symptoms, it is necessary to find an optimal combination adapted to the patient and their pathology, since more effective combinations have been found than others.

Three groups of treatments

The most recommended first-line medications include antidepressants and neuromodulators, as well as local anesthetics.

• The antidepressant may be tricyclic (act on norepinephrine), which have been prescribed for more than 25 years for this disease or dual (act on receptors of serotonin and norepinephrine).

• The neuromodulators decrease glutamate release, norepinephrine and substance p. These include pain relievers, anxiolytics, and antiepileptics.
• They are also highly recommended the locale anesthetics s in gel or lidocaine patches. When the pain is localized they are an excellent option because it is a safe and effective method.

Second-line medications include opioids . For a long period they have been the subject of controversy, but due to the efficacy shown there are cases in which it is prescribed individually or in combination with other drugs.

The anticonvulsants and antidepressants are the group of third line, with those who submitted less effective.

Non-pharmacological treatments

In addition to these treatments, in some cases it is also advisable to go to manual therapies, acupuncture, physiotherapy, etc. Likewise, psychological therapy can help alleviate psychological disorders and improve quality of life.

However, the most important thing in the treatment of neuropathic pain is to carry out updates and revaluations of it, in order to see to what extent it is working for the patient. In the event that several ineffective treatments have been tried, the most appropriate would be to refer the patient to a Pain Unit to assess other interventions.