Assessment of the efficacy of Electronic Nerve Modulation (ENM) in comparison to TENS in patients with chronic low back pain

This data was presented at the 10th National Pain Conference on Pain Management Programmes, Nottingham, UK, September 2005 and further Published in Neuromodulation; Volume 9; April 2006

Authors: Dr S Kapur, SpR Anaesthesia, Dr A Bennett, Consultant in Anaesthesia & Pain Management, Sister Sharon Williams, Pain Nurse Specialist

Institution: Dept of Anaesthesia & Pain Management, Worcester Royal Hospital, Charles Hasting Way, Newtown Road, Worcester, WR5 1DD

Background:  Transcutaneous Electrical Nerve Stimulation (TENS) has been widely used for treatment of chronic back pain but suffers from limitations such as decreasing effectiveness over time, difficulty with correct electrode placement, brief post-stimulation relief and uncomfortable sensation of muscle spasm, especially at higher voltages.  ENM offers theoretical benefits over TENS in that the pulses are delivered at a much higher frequency and shorter wavelength, therefore allowing deeper tissue penetration and higher voltages to be used before the threshold of painful sensation is reached.  Moreover, there are only two sites for electrode placement, potentially making correct placement easier.  However, there has been relatively little work on comparing the efficacy of the two modalities of treatment.

Methods:  Telephonic interviews were conducted with 28 patients on the pain clinic database who had used both TENS and ENM for their chronic back pain.  These patients had to satisfy the following criteria:

• Chronic low back pain
• Patients had to have used both TENS & ENM within the past 2 years
• Not on any opiates
• No corrective surgery since being on TENS / ENM
• Seen in pain clinic within the last 6 months

A 5 point questionnaire was administered by a single interviewer:

• Which device are you currently using & how much pain relief does it provide (VAS 0-10)?
• How much pain relief did the other device provide (VAS 0-10)?
• Which device is better for your pain and why?
• Has the efficacy decreased over time?
• Any side effects with either device?

Results: 28 patients were contacted.  Of these, 3 (on ENM) could not recall using TENS & 3 (on TENS) couldn’t recall being on ENM.  22 patients could provide information on both:

• Found ENM better = 15 patients (Average VAS: TENS 2-3/10, ENM 5-8/10)
• Found TENS Better = 1 patient
• Found both useful in different ways = 1
• Found no effect with either TENS or ENM = 5 (All 5 had Fibromyalgia)
• Found TENS aggravated the pain = 6
• Duration of pain relief = 1-3 days with ENM, 2-12 hours with TENS
• Found ENM easier to use = 17

Conclusions: The result of this study indicate that ENM does appear to provide better relief than TENS for Chronic low back pain.  Moreover a large percentage of patients in this study found ENM had fewer side effects compared to TENS and that the pain relief from ENM appeared to last longer.  Patients also found ENM easier to use. 

ENM : Qualitative Self - Assessment by Users

This data was first distributed at the Pain Society meeting, Edinburgh on 9th March 2005.

"From the clinical point of view the message is clear:- believe the patient" (McQuay & Moore)

We asked them and this paper represents the analysis of 428 completed questionnaires from patients using ENM over 3 months.

Method

Questionnaires were sent out to over 500 patients who had acquired ENM devices in May 2004. The results were analysed for changes in pain score, quality of life and changes in sleep patterns.

For simplicity, patients were given 3 choices within each parameter:-

0 = No improvement or insignificant improvement
1 = Significant improvement
2 = Substantial improvement

Analysis of data

Results

19.6% of patients suffered from more than one condition.
36.8% of those with fibromyalgia reported more than one condition.

Conclusion

So now we know, the patients tell us that their pain level improves, their sleep patterns improve and their quality of life improves.

Electronic Nerve Modulation is acceptable and effective when used by patients in their own homes without medical supervision. Initial diagnosis of the cause of chronic pain does not seem to be a significant predictor of outcome.

EFFICACY OF ELECTRONIC NERVE MODULATION IN PATIENTS WITH CHRONIC PAIN: A DOUBLE BLIND, PLACEBO-CONTROLLED CROSSOVER TRIAL

Presenting author Dr John Royle LRCP, MRCS, Great Harwood Health Centre, Lancashire

This trial was first presented at the Pain Society meeting, Manchester on 30th March 2004

Introduction and Aim
The complexities of managing chronic pain in the community can demand a multi-faceted treatment approach. Electroanalgesia is among the options available. Most chronic pain patients are introduced to electroanalgesia via TENS. TENS devices stimulate the peripheral nerves, but limitations may include failure to resolve large tender areas as only a limited number of A§ fibres may be stimulated at any one time, difficulty with electrode placement and only a brief post-stimulation relief period.

At electroanalgesia’s other extreme, a study first published in 1971 by Sheeley described how he implanted wires into patients’ spinal columns to induce analgesia via the central nervous system. Since then, his technique of Dorsal or Spinal Column Stimulation (DCS/SCS) has been used extensively world-wide, with no reports of serious side-effects due to the treatment itself. However, DCS/SCS requires potentially hazardous neurosurgery, which is also expensive and time consuming.

Recognising these shortcomings and therefore as an alternative to both TENS and DCS/SCS, Transcutaneous Spinal Electro Analgesia (TSE) to effect pain relief again via the spinal column route was introduced in 1995. It involved applying electrode pads at T1 and T10, positions claimed as standard for pain anywhere in the body, which were connected by wires to a device emitting high voltage, short waveform currents. Although anecdotal and statistical information was encouraging, trial evidence was less so. Subsequently, research into iontophoresis has suggested ways of increasing the effectiveness of spinal electroanalgesia without the risks associated with high frequencies (e.g. skin heating/burning). This new technology is termed Electronic Nerve Modulation (ENM) and the aim of this study was to assess its efficacy in reducing pain in chronic pain patients at home and to assess any effect on the perceived quality of their sleep. Procedure and Method After submission to the North West Peer Review System, ethical permission was granted by the local ethics committee to perform a double blind, placebo controlled, cross over trial to establish the efficacy of Electronic Nerve Modulation in patients with chronic pain.

Parameters of the ENM devices used in this trial

• Alternate positive and negative pulses
• Each pulse up to 15µ seconds
• Up to 5µ seconds pause between pulses
• Pulse voltage 80 to 120 volts/pulse
• Frequency 2,700Hz +/- 15%
  (All measurements conducted with a 1 kilo ohm load resistor)

Recruitment
Due to my known interest in electroanalgesia, the ethics committee requested that recruitment should be undertaken by a doctor unconnected with the trial. Dr David Smith (now retired), a single handed GP of the Health Centre, Great Harwood, Nr Blackburn, recruited 20 patients with a history of chronic pain lasting in excess of 6 months.

Inclusion criteria:
- Age 16 to 80-years-old
- Ability to apply electrode pads in correct position
- History of chronic pain exceeding 6 months

Exclusion Criteria:
- Pacemakers
- Pregnancy
- Severe disability
- Patients with a history of adverse reactions to electrode pads or adhesive gel

Informed consent forms were completed by all subjects.
Participants were supplied with an ENM device, set of pads and a set of leads, which were either active or placebo. As ENM causes no sensation whatsoever to the patient, the trial was blind. The leads were coded and supplied directly to the subject by the project administrator. The clinician was thus blinded to their status (i.e. active or placebo). Detailed written and diagrammatic instructions about electrode placements were given to each subject. In short the pads were to be applied to the skin over the first and tenth thoracic vertebrae.

Before commencing the trial, subjects completed:
- Quality of Life Questionnaire (GP Research Unit 1972)
- Pain Assessment Chart (McGill Shortform)
- Medication form

Week 1
Subjects used the device for 1/2 hour each morning and 1 hour each evening. A detailed patient diary was provided in which to record pain and mood before and after each treatment, as well as a summary of the level of pain each day. On completion of week 1, Quality of Life, Pain Assessment and Medication sheets were completed.
Primary outcome measure: Change in quantity of pain as determined by VAS.
A wash out period of 4 days was observed. Prior to week 2, completion of Quality of Life, Pain Assessment and Medication Sheets was required.

Week 2
Exchange of leads -- Repeat week 1
On completion of week 2, Quality of Life, Pain Assessment and Medication sheets were again completed. Primary outcome measure: Change in quantity of pain as determined by VAS.

Outcome and Results
Of the 20 patients recruited, 15 completed the investigation. Of those failing to complete, two withdrew from the trial before commencement, one failed on paperwork and was withdrawn and two finished week 1 before withdrawing from the trial. Of these, both felt sure they had been using active leads and did not wish to be supplied with placebo leads for week 2 (when the code was broken, both were found to have correctly assessed the situation).

The overall assessment of pain recorded in the patient diary for day 1 of the week was compared with the overall assessment of pain for day 7. All such assessments were on a 1 to 10 VAS.
- Placebo leads report total improvement of –6 points. Ave 0.4 points worse
- Active leads report total improvement of +21 points. Ave 1.4 points improvement
- The overall difference = 1.8, representing an improvement of 38.3% (this is statistically significant
(p=0.03)).

During active treatment, 10 patients had improved pain scores (total improvement +21 points, average 1.4 point improvement) and five remained the same. During placebo treatment, five worsened, six stayed the same and four improved. On sleep scores, active treatment assessment shows 12 improved (average 2.88 points),two stayed the same and one worsened, while six worsened, two stayed the same and seven improved (average 1.03 points) during placebo treatment.
Although medication intake and QOL measures are still to be analysed, of the 15 completing patients, 13 (86.6%) had derived benefit from EMN (either pain relief or better sleep).

Discussion and Conclusion
It would be easy to assume patients sleep better only because they are in less pain. Yet of the six patients reporting improved sleep scores > 3 points, 50% (three) filed no improvement in their pain scores. This suggests ENM may help with sleep even when providing no pain relief and demands further investigation in its own right. However, this trial indicates that ENM may be an effective way for chronic pain patients to control symptoms in the home. Trial patients reported the device easy to use – 14 out of the 15 completing patients, plus the two withdrawn after completing week 1 only, wished to continue ENM therapy at the trial’s end.