SCS for Gastrointestinal Pain

From a study in 2000, of those treated for chronic pain, 14% were due to abdominal pain and 3% due to pelvic pain. This compares to 10% for fibromyalgia. It was also shown that 30% of the population has either pain as a disease or chronic disease-related pain.

Pain from viscera:
1. Is poorly localized
2. Is referred to other areas of the body
3. Is not evoked from all viscera
4. Is not necessarily evoked from visceral injury
5. Produces non-specific or whole body motor responses
6. Produces strong autonomic responses
7. Leads to sensitization of body structures
8. Produces strong affective responses

Note that not all internal organs are sinsitive to pain and some can be damaged quite extensively without the person feeling any pain b/c some organs lack nociceptors. Hollow viscera have nociceptors and solid organs lack them.


NEUROBIOLOGY OF VISCERAL PAIN

Visceral nociceptors respond to intense mechanical stimuli (stretching and distension), irritant chemicals, and inflammatory products. Some visceral nociceptors are "silent" and become active only after inflammation occurs.

Uncontrolled visceral pain can lead to visceral hyperalgesia, an incerased sensitivity to visceral stimulation following an injury/inflammation of an internal organ. The increased sensitivity of the viscera after inflammation has two causes:
1. an alteration of the sensory neurons in the viscera where they respond more intensely to a usually non-painful stimulus (peripheral sensitization)
2. an enhanced sensitivity of teh sensory pathways in the brain that medicate sensations from the viscera (central sensitization)

In central sensitization, Wide Dynamic Range Neurons (WDR) are activated by repetitive stimulation from C-fibers, but not A-delta fibers, causing a steady increase in WDR activity until, at some point, the WDR neuron fires independently of the nociceptive input. This action is called "windup."


SPINAL CORD STIMULATION HAS ALSO BEEN CALLED "DORSAL COLUMN STIMULATION."

Based upon this thought, and the fact that visceral nociceptors synapse in Rexed laminae 4, clinical studies have shown that the dorsal column pathway is important in visceral pain transmission. (Palecek and Willis. Pain 2003;104:501-507 Ness. Pain 2000;87:83-88) Posterior midline myelotomies by Hirshberg have shown to relieve pelvic cancer pain without neuorologic deficits. It is further noted that disruption of th dorsal column pathway reduces responses of neurons in the VPL of the thalamus.

Kapural and Mekhail from the Cleveland Clinic have submitted an article showing that SCS is effective in severe pelvic pain.

Opioid Potency Comparison http://book.pallcare.info/index.php?tid=125

This information comes from:
Elliot Krames, MD
Pacific Pain Treatment Center
San Francisco, CA