Background and aims: 
Recent data suggest that by changing the Spinal cord stimulation (SCS) pattern or by increasing the pulse width of SCS current and delivering this in bursts, equal or better pain relief can be obtained at current amplitude below sensory threshold, i.e. without paraesthesia. The aim of this study is to compare the efficacy of burst (BST) and tonic sub-threshold stimulation at 500Hz (T500) versus sham stimulation delivered by a device capable of automated postural adjustment of current intensity  .

Methods: 
The study is a randomised double blind, 3-period 3-treatment crossover multicentre study. After randomisation, BST, T500 and Sham SCS were initiated in a double blind randomised crossover design. Patients reported a) pain intensity (VAS), b) patient global impression of change (PGIC), and c) health related quality of life (EQ5-D).

Results:
19 subjects in total were recruited from 2 UK sites (Department Pain Clinic at the James Cook University Hospital Middlesbrough & Newcastle upon Tyne Hospitals UK (NuTH)), demographic characteristics are in Table 1.

Table 1. Descriptive characteristics at baseline

Variable	Summary statistic
Sex (n)	7 men/ 12 women
Site (n)	10 JCUH/ 9 NuTH
Clinic usual Pain VAS (cm), mean (SD) (n=17)	4.4 (2.2)
EQ5-D index, median (interquartile range) (n=17)	0.620 (0.516 to 0.691)

Following recruitment 9 cases were available to assess response to Tonic vs. Sham and 11 for response to Burst vs. Sham. 

The mean reduction in pain for Tonic vs. Sham was 25% (95% CI, 8 to 38%; P=0.008). Pain VAS in Burst was 5% higher than Sham (95% CI, -13 to 27%; P=0.59).
Sub-group analyses by study site and sex were also conducted for the Tonic vs. Sham and Burst vs. Sham comparisons

Conclusions: 
The findings demonstrate a superior outcome from T500 stimulation over BST stimulation in a group of subjects with leg and back pain habituated to tonic SCS and having achieved a stable status with stimulation. It is difficult to explain why our findings are at odds with previous studies of similar design (1), however the speculate that the use of adaptive stimulation may be a factor , another explanation may be small study size.


1.	Schu S, Slotty PJ, Bara G, von Knop M, Edgar D, Vesper J. A Prospective, Randomised, Double-blind, Placebo-controlled Study to Examine the Effectiveness of Burst Spinal Cord Stimulation Patterns for the Treatment of Failed Back Surgery Syndrome. Neuromodulation. 2014;17(5):443-50.

ANALGESIC EFFICACY OF &#8220;BURST&#8221; AND TONIC (500HZ) SPINAL CORD STIMULATION PATTERNS: A RANDOMISED PLACEBO-CONTROLLED STUDY

ANALGESIC EFFICACY OF “BURST” AND TONIC (500HZ) SPINAL CORD STIMULATION PATTERNS: A RANDOMISED PLACEBO-CONTROLLED STUDY