Continuous versus intermittent spinal cord stimulation: an analysis of factors influencing clinical efficacy

Spinal cord stimulation (SCS) has, for decades, been shown to be successful in a variety of chronic neuropathic pain syndromes. However, there is a paucity of reports in the literature comparing different stimulation patterns. The impact of different stimulation patterns upon outcome remains to be determined, as well as how the latter is influenced by the duration of the post-SCS pain-free interval.

Data from 61 patients (of 71 eligible patients) were collected by means of a telephone interview. These data included the pattern of stimulation (intermittent or continuous), the intensity of stimulation with regard to threshold, the mean, maximal, and minimal pain strength on a numerical rating scale with and without stimulation, the average duration and number of daily stimulation intervals, the average duration of the pain-relieving effect after switching off the impulse generator, the pain medication intake, the extent of paresthesia coverage, unpleasant side effects, and patient satisfaction.

The average improvement in pain score following SCS was 3.10 (50.61%). Twenty-four patients (39.3%) performed continuous stimulation, and 37 patients (60.7%) performed intermittent stimulation. Patients who performed continuous stimulation had significantly shorter pain-free intervals following the cessation of stimulation. These patients also showed a tendency toward higher pain scores with and without stimulation, which was not statistically significant. There were no significant differences in pain scores, duration of pain relief, and usage of the stimulation system between patients with different diagnoses and lead locations.

Our data showed an equal effectiveness of SCS in the intermittent and in the continuous stimulation mode. The duration of the post-SCS pain-free interval may be predictive for the choice of the most effective individual stimulation pattern and deserves further investigation.