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CHAPTER 96  Spinal Cord Stimulation

Vagus nerve

STT

Dorsal roots

SCS Lead

A

A

FIGURE 96.5  Schematic illustration of some mechanisms possibly involved in the effects of spinal cord stimulation (SCS) on coronary isch- emic pain. SCS might exert indirect inhibitory effects on nociceptive transmission to higher centers and on the level of sympathetic activity; SCS might also have antidromically transmitted effects. Intrinsic cardiac nervous system (ICNS) are deeply involved in monitoring ischemic events in the heart, and this function is drastically influ- enced by SCS. The interplay between somatosen- sory and autonomic influences and the effects of SCS is presently largely unknown but is the sub- ject of intense investigation. DC, dorsal columns; STT, spinothalamic tract.

DC

c

ICN

?

?

Sympathetic Efferent Fibers

Organ Involved

SCS Effect

SCS

1. Bronchodilation

1

C2

Cervical

2

3

2. Peripheral vasodilation

T1

High thoracic

4

3. Stabilization of ICNS Reduction of ischemia and pain Decreased infarct size

Middle thoracic

5

4. Decreased colonic spasms Pain Reduction

L1

Low thoracic

6

5. Peripheral vasodilation

6. Decreased bladder Spasticity Increased volume tolerance

S1

Sacral

FIGURE 96.6  Spinal cord stimulation (SCS) applied at different levels of the neuraxis might, in addition to affecting pain and peripheral blood flow, induce changes in different target organs mediated via stimulation induced changes in local autonomic activity, dorsal root reflexes, or viscerosomatic eflexes. Some of these changes in target organ function might be beneficial. ICNS, intrinsic cardiac nervous system. (Redrawn after Linderoth B, Foreman RD. Mechanisms of spinal cord stimulation in painful syndromes: role of animal models. Pain Med 2006;7:514–526).