Hyperpathia, hyperalgesia, and allodynia are three manifestations of central sensitization, a condition in which a higher than necessary degree of activity is triggered in the central nervous system. Generally, this activity is triggered by nocioception or the nervous system's normal response to painful stimuli.
Comprised of the brain and spinal cord, the job of the central nervous system is to take information in from the outside, for example, hot or cold sensations, or sensations about the position your body is in, process it and then issue a movement response to it.
If you touch a boiling pot, your automatic response will likely be to withdraw your hand from the pot as soon as possible. This is the central nervous system in action.
In cases of central sensitization, once this extra activity is triggered, it may last for quite a while. The good news, though, is this condition can be reversed.
The word hyperpathia describes an exaggerated reaction to stimuli. In other words, with hyperpathia, your reaction to a stimulus, especially a repeating one, is increased. Such stimuli include touch, vibration, pinpricks, heat, cold, and pressure. Your pain threshold is increased, as well.
When you have hypathia, you may find that you identify and/or locate the painful stimulus erroneously, or there may be a delay between when you come into contact with the stimulus and when you experience it. The pain may radiate, and there may be some after effects, as well. And it may have an explosive quality to it.
Hyperpathia lowers your pain threshold, increasing your sensitivity to things you physically feel. It is similar to hyperalgesia, with the addition that the feeling of pain continues even after the stimulus that causes it has been removed.
To Understand Hyperpathia, Look to Hyperalgesia
To understand hyperpathia, it's probably a good idea to start with hyperalgesia, as this is a predominant type of neuropathic pain and often accompanied by hyperalgesia.
Hyperalgesia is an augmented pain response. In other words, with hyperalgesia, there is increased pain response to a painful stimulus. Your pain threshold may be lowered, as well.
Hyperalgesia is similar to hyperpathia except that the increased response is to painful stimuli. Hyperpathia, on the other hand, is an augmented response to any sensory stimuli.
Hyperalgesia is classified into subtypes that relate to the type of stimuli causing the response. These include the stimuli mentioned above, in other words, thermal sensations, pressure, touch and more. Each subtype has its own way of working, which is called a mechanism.
Somewhere between fifteen and fifty of percent patients with nerve pain experience hyperalgesia, according to a 2014 study in the British medical journal, The Lancet.
Does Your Psychological State Affect Your Back Pain Levels?
If you’ve been traumatized psychologically your risk for a chronic back problem may be increased — even if you don’t have PTSD. (Scientists have found an association between PTSD and chronic back pain risk.) That said, pain specialists are unclear about the role that psychological trauma plays in nonspecific chronic low back pain.
In a 2014 study published in the journal Pain, researchers concluded that people with hyperalgesia who also experienced psychological trauma had lower pain thresholds in general. This means that both painful areas, i.e., their backs, and non-painful areas such as their hands experienced lowered pain thresholds.
While study participants with hyperalgesia who had not experienced psychological trauma also had lower pain thresholds, their lowered thresholds were limited to just those areas already affected by pain, which, in this case, was their low backs.
Allodynia is central sensitization pain response to stimuli that normally do not provoke pain. For example, for most people, stroking a cat is a pleasurable experience. It is not associated with the feeling of pain. But in cases of allodynia, that same action of petting your kitty may bring on pain.