Electric Muscle Stimulation Better than TENS for Neuropathy

Effective treatment of symptomatic diabetic polyneuropathy by high-frequency external muscle stimulation. Diabetologia. 2005 May;48(5):824-8.  Reichstein L, Labrenz S, Ziegler D, Martin S.

Abstract
AIMS/HYPOTHESIS:
Diabetic distal symmetrical sensory polyneuropathy (DSP) affects 20-30% of diabetic patients. Transcutaneous electrical nerve stimulation (TENS) and electrical spinal cord stimulation have been proposed as physical therapies. We performed a controlled, randomised pilot trial to compare the effects of high-frequency external muscle stimulation (HF) with those of TENS in patients with symptomatic DSP.

 
METHODS:
Patients with type 2 diabetes and DSP (n=41) were randomised to receive treatment with TENS or HF using strata for non-painful (n=20) and painful sensory symptoms (n=21). Both lower extremities were treated for 30 min daily for three consecutive days. The patients’ degree of symptoms and pain were graded daily on a scale of one to ten, before, during and 2 days after treatment termination. Responders were defined by the alleviation of one or more symptoms by at least three points.

 
RESULTS:
The two treatment groups were similar in terms of baseline characteristics, such as age, duration of diabetes, neurological symptoms scores and neurological disability scores. The responder rate was significantly higher (p<0.05) in the HF group (80%, 16 out of 20) than in the TENS group (33%, seven out of 21). Subgroup analysis revealed that HF was more effective than TENS in relieving the symptoms of non-painful neuropathy (HF: 100%, seven out of seven; TENS: 44%, four out of nine; p<0.05) and painful neuropathy (HF: 69%, nine out of 13; TENS: 25%, three out of 12; p<0.05). The responders did not differ in terms of the reduction in mean symptom intensity during the trial.

 
CONCLUSIONS/INTERPRETATION:
This pilot study shows, for the first time, that HF can ameliorate the discomfort and pain associated with DSP, and suggests that HF is more effective than TENS. External muscle stimulation offers a new therapeutic option for DSP.

My comments:

I would have really liked this study had it shown great results with the high frequency (HF) electric stimulation, and compared it to TENS and found the HF worked considerably better. The next study I am going to cite uses the exact same HF machine and calls it EMS (electric muscle stimulation) rather than HF, and that fits with my observations and other research that EMS works better than TENS to control pain.

What I don’t like about this study, however, is that from the description of the parameters I can’t figure out what they used. Plus, other things besides the current are different, including electrode size and placement.

For the TENS group I get:

  • Waveform: biphasic exponentially decaying
  • Duty Cycle: continuous (I think)
  • Pulse Duration: 400 uS
  • Intensity: 20-30 mA
  • Rate: 180 Hz
  • Treatment Length: 30 min
  • Training Frequency: daily
  • Training Length: 3 days
  • Electrodes: two sticky ~2” electrodes per leg, placed on proximal and distal fibula region

For the HS group:

  • Waveform: biphasic exponentially decaying
  • Duty Cycle: 3 sec ramp, 3 sec on (3 sec off I think, because that’s what the next study using the same machine reports)
  • Pulse Duration: does not say but with the high Hz I expect its pretty short
  • Intensity: adjusted to a pleasant level without pain or uncomfortable paresthesia
  • Rate: 4096 Hz – 32768
  • Treatment Length: 30 min
  • Training Frequency: daily
  • Training Length: 3 days
  • Electrodes: two carbon ~3.5” rubber carbon electrodes per leg, placed on the proximal and distal quadriceps.

So in this study the HS group did a lot better, but it is hard to tell if it is due to the difference in current, or the larger electrodes being used in the HS group, or the HS group putting the electrodes over a muscle rather than a bony region. I would expect the larger electrodes to work better because you can turn the machine up higher with greater patient comfort because of lesser current density (coulumbs delivered per square inch of skin). Also I don’t think it’s at all ideal to place the smaller electrodes over the bony region of the fibula, though I find it interesting that the larger electrodes on the quadriceps worked so well since presumably the diabetic neuropathy sufferers were complaining of the most pain and paresthesias in the feet. Another interesting thing is the good results of the HS group was noticed in just 3 days of treatment, which is in accordance with my observation using EMS. My patients report relief immediately after my 12 minute treatment, and those results continue to improve with future treatments. Also interesting from this study is they treated people with both painful and non painful neuropathy, noting it worked on non-painful neuropathy better. My patients tend to report similar improvements painful or not with my protocol, but that could be due to the different parameters where I’m using 4 electrodes per leg instead of two, placing all the electrodes on muscle (including the bottom of the foot), my electrodes are larger still, and I use as long a pulse width as my machines allow (300-450 uS) for as high an intensity as they can tolerate.  

So the take home message for me is that all stimulation parameters are not equal, but in this study it is unclear which part of the different stimulation protocols led to the difference in effects. I suspect that greater intensity of stimulation, and on and off period, larger electrodes, placing the electrodes over muscle all contributed to better outcomes in the latter group.  

As always, if you have any further questions or need for clarifications, please don’t hesitate to ask. Being aware that some of my blog ideas are contentious and occasionally a bit out of the field of my expertise, I encourage my readers to come forth with any questions/comments that are of interest or concern. Your comments are valued and welcomed.

Chad Reilly is a licensed physical therapist, located in North Phoenix, practicing science based medicine with treatment protocols unique and effective enough to proudly serve patients from Phoenix, Scottsdale, Mesa, Chandler, Tempe, Peoria, and Glendale.

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