Causalgias are divided into two forms:
1. Causalgia major involves peripheral nerve injury with electrical "crosstalk" (ephapse) that causes severe hyperactivity of sympathetic system (hyperpathia, vasoconstriction, and movement disorder). The major form is severe, usually caused by injury with high velocity sharp objects (e.g., butcher's knife), vibratory component major trauma (e.g., bullet), or high-voltage nerve lesions (electrocution).
2. Causalgia minor involves the same principle as causalgia major, but milder injury, e.g., injury to the dorsum of hand or foot, nerve root contusion, patient falling from a height on gluteal region resulting in "guillotine" effect, bruising of nerve root caught at the narrowed intervertebral foramen.
SO,The difference between the two categories is a matter of degree and severity. To classify causalgia as an independent illness is artificial, and causalgia is nothing but a sever form of RSD(Reflex Sympathetic Dystrophy ).
In this severe form of RSD, the course of the disease is quite accelerated from stage 1 through 4 in a matter of weeks or months. S. Weir Mitchell in 1872 first reported rapid development of atrophic changes in the skin, nails, and soft tissues of the extremity in a matter of days to weeks.
Whereas in RSD of disuse the extremity is cold, in ephaptic dystrophy the thermography reveals in the distal portion of the extremely cold extremity that there is an isolated hot spot that points to the area of scar formation and ephaptic peripheral nerve dysfunction . In this area the vasoconstrictive capability of the sympathetic nerve is paralyzed, and there is a topical hot spot. This hot spot can be appreciated only by thermograph.
CAUSALGIC PAIN:
- Usually pain occurs after the injury to a nerve trunk.
- The pain is spontaneous, severe, and quite persistent.
- There is a markedly lowered threshold for aggravation of pain. This is the case in all RSD patients, but it is more exaggerated in causalgics. So even a breeze over the skin or the touch of a bed sheet or a change of the environment or a family argument and aggravation can markedly aggravate the pain. This feature of emotional aggravation is common to all RSD patients, and it is nothing but the role of the frontal lobe and the limbic system in aggravation of hyperpathic pain.
- The pain is felt distal to the proximal nerve injury, i.e., in the hand or foot. This is typical but not invariable. The pain does not necessarily have to be a burning type of pain, and can be described in many other hyperpathic forms.