Does Inflammation Precede the Changes which lead to Central Pain?

The implications of Hohmann et al in Dec 2005 J Pain are almost staggering.

Researchers have now found that inflammation in lab animals at day 0 of fetal birth causes profound changes in painful sensory processing during the remainder of life. Inflammation at day 14 does NOT cause these changes. These changes were measured, among other ways, by studying the amount of Cfos being expressed in the superficial dorsal horn with noxious stimulus. Cfos is an intermediate early marker commonly used to indicate gene activity. This study makes us curious what is happening to the ion channels in these animals and whether Nav1.3, the sodium ion channel of fetuses and of central pain, is in any way altered.

We have long made inquiry into environmental factors that might explain why one subject with SCI developed Central Pain and another did not. This study by Hohmann et al is more than shocking. It suggests to us the very important question of whether some element of inflammation may spell the difference between simple spinal cord injury and SCI which is followed by Central Pain.

The reason such a finding is important is that from time to time questions have arisen about the value of steroids, which reduce inflammation in spinal cord injury. It also raises the question of how long steroids should be continued. For example, some steroids may last nearly a year. Perhaps they should be considered over the sort acting ones. We have reports in the surveys of central pain occurring more than two years after injury.

It is important to sort this matter out. We have received reports of patients receiving long acting steroids such as triamcinolone (Kenalog), up to 160 mg. At these dosages, the patient retained about 20 lbs of fluid for two months or more, had trouble sleeping, experienced considerable muscle weakness, and for the first week was excitable, possibly because steroids cause stored glycogen to revert to glucse to be burned.

At any rate, we would welcome more studies on early steroid injection, the type of steroid used (a single dose of dexamethasone is common) and the resulting comparative rates of development of central pain.