Efficacy of spinal cord stimulation for neuropathic pain: assessment by abstinence

Assessment of the efficacy of spinal cord stimulation (SCS) against neuropathic pain remains problematic. Some patients may underestimate this, as revealed by their reaction to stimulator malfunction. This study investigated whether abstinence from SCS would provide an indication of its effectiveness. Patients were invited to complete two brief questionnaires each day for 50 days including two periods of 14 days without stimulation. Pain level, sleep quality, activity level and drug intake were recorded. Of 75 patients thought to be using their stimulators, 12 did not respond to the invitation, eight had unresolved technical problems and one no longer needed SCS. Of the 54 remaining, 10 did not wish to be without SCS and 15 declined without giving a reason. Thus 29 agreed to take part but three then dropped out through illness and questionnaires were not received from 10. Ten returned completed questionnaires but failed to follow the protocol; five of these were unable to leave their stimulators off. Only six took part correctly. Twenty of the 29 had received a preliminary explanatory home visit and for nine this was done by telephone. The former produced a considerably higher yield. All six who completed the study correctly had statistically significantly lower pain scores during stimulation. Four had improved sleep but only one reduced his medication and none of the six increased their activity levels. Correlation with previous clinical assessments is discussed. It is concluded that the abstinence principle might provide a useful tool but its power is very methodology-dependent.