Recent research shows that while spinal cord stimulation is effective at relieving chronic neuropathic pain such as that associated with failed back surgery syndrome (FBBS), it has little or no effect on the processing of acute experimental pain.
Failed back surgery syndrome (FBSS) is when a patient feels persistent or reoccurring neuropathic pain of the lower back and/or legs after having undergone spinal surgery. FBSS affects around 30% of spinal surgery patients, who then face increasing disability and chronic pain. FBSS patients often experience a number of associated problems including sleeping problems, depression and high-dose painkiller dependence. It is also unlikely that further surgery will provide any relief for FBSS sufferers.
Spinal cord stimulation (SCS) involves electrical stimulation of sensitive areas in the spinal cord that are involved in sending pain signals to the brain. The long-term use of SCS has been shown to relieve neuropathic pain in over 50% of FBSS patients. SCS is generally a very safe procedure with only a small chance of very minor complications occurring.
It is well known that long term SCS can provide pain relief for people experiencing chronic neuropathic pain such as FBSS sufferers. What is not clear, however, is whether SCS can provide pain relief for acute pain.
Functional magnetic resonance imaging (fMRI) enables us to see blood flow patterns in the brain. This means that we can see which regions of the brain are active at a particular time.
A research group from the Czech Republic has recently used fMRI to see brain activation patterns in people undergoing SCS. They were also interested in whether these brain activation patterns were different when people were subject to acute heat pain (HP) at the same time as SCS. If the patterns remained the same it could mean that SCS can stop someone feeling acute pain as well as chronic pain. This could be dangerous because there is a chance that the person may injure (eg. burn) himself or herself without knowing it.
Eight patients suffering from failed back surgery syndrome (FBSS), already being treated with SCS for severe leg and lower back pain, were involved in the study. The patients were subjected to three types of stimulation 1) SCS, 2) heat pain (HP) and 3) simultaneous SCS and HP, with each stimulation lasting 36 seconds. Following the experiment and fMRI analysis, each patient was asked to evaluate the intensity of the heat pain during the periods with and without SCS.
FMRI scans showed increased activity in a region of the brain corresponding to the foot and/or perineal region. Statistically significant activation of the region of the brain associated with pain sensing were seen when patients were subjected to SCS and acute HP at the same time. These results suggest that SCS has little or no effect on stopping someone from feeling acute pain.
- People underwent SCS with or without heat pain (HP) stimulation in order to analyse activation patterns in the brain that are associated with processing SCS and acute experimental pain.
- Simultaneous acute HP and SCS resulted in statistically significant activation of regions in the brain associated with processing pain signals.
- The effects of SCS on the processing of acute pain are relatively small.
- Stancak A, Kozak J, Vrba I, Tintera J, Vrana J, Polacek H, et al. Functional magnetic resonance imaging of cerebral activation during spinal cord stimulation in failed back surgery syndrome patients. Eur J Pain. 2008; 12(2): 137-48.