Italian researchers have reported through a new study that they have “direct evidence” for central sensitization in Interstitial Cystitis patients.
Central sensitization—essentially amplification of pain signals in the central nervous system—is thought to contribute to perpetuation of pain—and possibly its initiation—in the condition.
This theory, if true, may help explain why IC Disease patients also suffer from other pain-related conditions such as Fibromyalgia and IBS. There was also recently another study that found that Interstitial Cystitis patients are also more likely to suffer from Vulvodynia – another pain-related condtiion.
This news on IC was recently presented at the International Continence Society annual meeting by Dr. Silvia Malaguti & Dr. Mauro Cervigni, both from Rome.
According to the study, these doctors…
…investigated spinal transmission of pain signals and diffuse noxious inhibitory controls in 14 IC/PBS patients—12 women and two men—and in 10 age- and sex-matched healthy controls. Diffuse noxious inhibitory control is the phenomenon of inhibition of perception of a painful stimulus by a second painful stimulus administered distally. In subjects who do not have chronic pain disorders, pain from the test stimulus is decreased or inhibited when a conditioning stimulus is applied at a distal site.
The investigators did this using the nociceptive flexion reflex (NFR) RIII and the cold pressor test (CPT), both of which are standard tests in pain research.
The NFR is administered by electrically stimulating the sural nerve. The test’s RIII, or long-latency, component is evoked by stimulation intense enough to activate the A-delta and C fibers responsible for transmission of pain signals. Thresholds for the reflex correlate strongly with subjective pain thresholds, and increases in NFR amplitude correlate with increases in subjective pain intensity.
In the CPT, the patient places a hand in ice water. The patient lets the researcher know when he/she first feel pain and then withdraws the hand when the pain becomes unbearable. This measures a threshold for and tolerance of this type of pain. In this study, the CPT was used as the noxious conditioning stimulus. The investigators measured the NFR RIII at baseline and then during the CPT.
What the research showed was that Interstitial Cystitis patients had significantly lower pain thresholds than that of the non-IC subjects in the study. The RIII reflex thresholds were also significantly lower than that of the non-IC subjects. But when the non-IC subjects did the test with placing their hands in ice water, their NFR RIII reflex was significantly inhibited (down 39%). In the IC patients, their NFR RIII reflex was stronger during this test and went up 35%.
Apparently, patients with IC/PBS do modulate pain differently from those without the condition.