Short- and long-term effects of conventional spinal cord stimulation on chronic pain and health perceptions: A longitudinal controlled trial.

BACKGROUND: The effectiveness and long-term outcomes of spinal cord stimulation (SCS) are not fully established, especially considering that data from patients who withdrew from the trial are rarely analysed, which may lead to overestimation of SCS efficacy. We evaluated short- and long-term effects of SCS on chronic pain and perceived health, beyond natural variability in these outcomes. METHODS: In a prospective design, 176 chronic pain patients referred to SCS were evaluated five times (baseline; retest ~6 weeks later; post-SCS trial; 8 and 28 weeks post-permanent implantation). Patients whose SCS trial failed (Temp group) were followed up and compared to those who underwent permanent SCS (Perm group). RESULTS: Analyses revealed a non-linear (U-shaped) trend significantly different between the two groups. In the Perm group, a significant improvement occurred post-SCS implantation in pain severity, pain interference, health-related quality of life and self-rated health, which was followed by gradual worsening and return to baseline values at end of follow-up. In the Temp group, only minor changes occurred in these outcomes over time. On average, baseline and end of follow-up values in the Perm and Temp groups were similar: ~40% in each group exhibited an increase in pain severity over time and 38% and 33%, respectively, exhibited reductions in pain severity over time. CONCLUSIONS: Since the greatest improvement in the outcome measures occurred from baseline to post-SCS trial (T1-T3) followed by a gradual decline in the effect, it appears that SCS may not be effective for the majority of chronic pain patients. SIGNIFICANCE: This longitudinal study evaluated short and long term effects of spinal cord stimulation (SCS) on chronic pain outcome measures, beyond their natural variation in time. Despite significant short term improvements, by the end of the seven months' follow-up, the outcomes in the treatment group (people who received the permanent implantation) were similar to those of the control group (people whose SCS trial failed and did not continue to permanent implantation) suggesting SCS may not be cost-effective for chronic pain patients.

Pain Perception and Body Awareness Among Individuals With Borderline Personality Disorder.

Studies indicate that individuals with borderline personality disorder (BPD) often demonstrate attenuated pain perception, termed hypoalgesia. This study examines the hypothesis that body awareness moderates the association between BPD and pain perception. Participants consisted of 46 women diagnosed with BPD and 47 healthy controls. Sensory testing included the measurement of heat-pain thresholds, ratings of suprathreshold stimuli, measurement of temperature evoking moderate pain, and temporal summation of noxious mechanical stimuli. Body awareness was assessed by a self-report questionnaire. As hypothesized, among subjects with low levels of body awareness, those with BPD demonstrated hypoalgesia as manifested in their lower suprathreshold pain ratings and moderate pain evoked by higher temperature, in comparison with the controls. Among those with high levels of body awareness, BPD subjects demonstrated increased reactivity to pain as manifested in their higher pain ratings and moderate pain evoked by lower temperature, in comparison with the controls.

Differentiating between heat pain intensities: the combined effect of multiple autonomic parameters.

Although it is well known that pain induces changes in autonomic parameters, the extent to which these changes correlate with the experience of pain is under debate. The aim of the present study was to compare a combination of multiple autonomic parameters and each parameter alone in their ability to differentiate among 4 categories of pain intensity. Tonic heat stimuli (1minute) were individually adjusted to induce no pain, low, medium, and high pain in 45 healthy volunteers. Electrocardiogram, photoplethysmogram, and galvanic skin response were recorded, and the following parameters were calculated: heart rate; heart rate variability-high frequency (0.15 to 0.4Hz) spectral power; skin conductance level; number of skin conduction fluctuations; and photoplethysmographic pulse wave amplitude. A combination of parameters was created by fitting an ordinal cumulative logit model to the data and using linear coefficients of the model. Friedman test with post-hoc Wilcoxon test were used to compare between pain intensity categories for every parameter alone and for their linear combination. All of the parameters successfully differentiated between no pain and all other pain categories. However, none of the parameters differentiated between all 3 pain categories (i.e., low and medium; medium and high; low and high). In contrast, the linear combination of parameters significantly differentiated not only between pain and no pain, but also between all pain categories (P<.001 to .02). These results suggest that multiparameter approaches should be further investigated to make progress toward reliable autonomic-based pain assessment.

Neuromodulation in the management of pain from brachial plexus injury.

We are presenting a paper on the effectiveness of spinal cord stimulation (SCS) in 2 patients suffering pain from brachial plexus injury (BPI). After a traumatic brachial plexus lesion about 80% of patients develop pain in the deafferentated arm. This pain is considered very resistant to many forms of therapy. In the early 1970s, SCS was introduced in the treatment of BPI pain with disappointing results. There are only about 20 published cases of BPI pain treated with SCS. Many injuries are due to motorcycle accidents, so that patients are often young and require long-term pain relief. During the SCS trial the pain relief was more than 50% with an absolute improvement in the quality of life and significant drug reduction. The results of the SCS were excellent in these 2 patients, defined as more than 50% pain relief at 6 and 18 months.