Among the advances and scientific knowledge brought by the 20th century is the detailed description of the physiological mechanisms that allow us to experience pain . From there, the latter has been defined taking into account different elements.

For example, according to its cause and specific course, pain has been divided into three main types: neuropathic, nociceptive and psychogenic . In this article we will see what the main characteristics of these types are, as well as the differences between neuropathic and nociceptive pain.

Types of pain and their characteristics

According to the International Association for the Study of Pain, “pain is an unpleasant sensory and emotional experience with actual or potential tissue damage or described in terms of such damage” (1994).

Depending on its functions and location, such a sensory and emotional experience can be classified in the following ways: nociceptive pain, neuropathic pain or psychogenic pain.

1. Noxious pain

Also known as somatic pain, nociceptive pain is defined as a normal response of the body to an offending stimulus , and is intended to prevent further damage. It is an adaptive pain, which is called nociceptive precisely because its main function is to perceive, alert and protect the organism from a noxious stimulus. An example would be to withdraw our hand when we begin to feel a hot object.

This type of pain is understood as a warning mechanism , an alarm signal or as an adaptive reaction to real or apparent harmful stimuli. The latter, the noxious stimuli, are transmitted through messages that are also known as “nociceptive messages”. They start in the periphery and move towards the dorsal shaft of the spine, and then towards different structures that allow it to reach the thalamus and the cortex (considered the higher centres of pain).

In the same way, nociceptive pain receptors can be found in the skin, muscles, joints or viscera. Therefore, it is a well localized pain that the person can write without much difficulty. A persistent experience of nociceptive pain can also cause a series of local sympathetic effects, muscle contractions and changes in posture .

2. Neuropathic pain

Neuropathic pain, on the other hand, is pain that is no longer considered an adaptive response, and is characterized by changes in the physiology of the response. This type of pain results from chronic lesions or alterations in peripheral or central nerve pathways. It develops in the face of a noxious stimulus, but can also do without it. For its description, people usually use unusual terms, while represents a new and difficult to describe experience .

It can occur in the following forms, which are also part of a hypersensitivity to pain known as hyperpathy:

  • Dysesthesia : basal sensation of pain, burning or stinging.
  • Hyperalgesia : as an excessive or exaggerated response.
  • Allodynia : through perceiving any stimulus as painful.

In addition, neuropathic pain can be divided into the following types depending on the specific location:

2.1.Pain of central origin

This can be the case, for example, with a cardiovascular accident or multiple sclerosis. Its location is in the central nervous system and is usually a pain that is more resistant to treatment .

2.2. Pain of peripheral origin

In this case it is a pain that has a generally favorable response to treatment and that originates in areas of the peripheral nervous system. Over time, this type of neuropathic pain can develop not only as peripheral pain but also as central pain, through a process that is precisely called “centralization” and is characterized by plastic changes in the posterior shaft of the spinal cord .

3. Psychogenic pain

Psychogenic pain is the psychological experience (e.g. anxiety or depression) described in terms of tissue damage. This description can be made in both verbal and behavioural terms, whether or not tissue damage has occurred. It is an experience of pain that has its genesis in a psychological state , and that is not localized in the organic structures of the nervous system.

Differences between neuropathic and nociceptive pain

Once the general characteristics of the different types of pain have been described, we can explain and summarize some differences between nociceptive and neuropathic pain. We follow Dagnino (1994) in the following five points.

1. The stimulus

In the case of nociceptive pain, the stimulus that causes the pain is evident and easily located by both the person experiencing it and the specialist. In the case of neuropathic pain, there is no obvious stimulus.

2. The location

Related to the above, the place where the pain occurs is easily located by the person experiencing it, so it is easily described. On the other hand, neuropathic pain is generally of diffuse location .

3. The description and its characteristics

The experience reported by people with nociceptive pain is often similar. On the other hand, the experience reported by people with neuropathic pain is difficult to report, seems to be an unusual and different pain, so it is more difficult to explain and may vary between each person.

4. The response to the narcotic

The differences in responses to drug treatment in both cases are also different. While in nociceptive pain an effective effect has been reported, in the case of neuropathic pain partial relief has been reported .

5. The response to placebos

In contrast, neuropathic pain often responds better to placebo-based treatments, and nociceptive pain responds virtually ineffectively. According to Dagnino (1994) the figures are 60% effective in the first case, and 20-30% in the second.

Bibliographic references:

  • ChangePain (2018) How is chronic pain defined? Recovered August 9, 2018. Available at http://www.change-pain.org/grt-change-pain-portal/change_pain_home/chronic_pain/insight/definition/es_ES/324800317.jsp.
  • Cruciani, R.A., Nieto, M.J. (2006). Physiopathology and treatment of neuropathic pain: most recent advances. Journal of the Spanish Pain Society. 5: 312-327.
  • Perena, M.J., Perena, M.F., Rodrigo-Royo, M.D., et al. Neuroanatomy of pain. Journal of the Spanish Pain Society (7)II: 5-10.
  • Dagnino, J. (1994). Definitions and classifications of pain. Medical School Bulletin. Catholic University of Chile. 23(3). Retrieved August 9, 2018. Available at http://www.arsmedica.cl/index.php/MED/
  • IASP (1994). Part III: (pp 209-214). Classification of Chronic Pain, Second Edition, IASP Task Force on Taxonomy, edited by H. Merskey and N. Bogduk, ISAP Press, Seattle, 1994. http://www.iasp-pain.org