How TSE Works and its Effectiveness
It
has been common practice to stimulate the spinal cord (dorsal column) through
the neurosurgical implantation of electrodes. Although there have been no
reported side-effects from this electrical device, infection associated with
the surgical implantation of wires and the stimulator is a long-term risk
factor that needs to be addressed. Dr Alexander Macdonald and Dr Tim Coates
sought to find a non-invasive method of spinal cord stimulation via surface
electrodes. To elicit a voltage gradient within the spinal cord, the
electrodes need to provide a current of sufficient amplitude to penetrate the
tissues that lie between the skin and spinal cord. Existing electrotherapeutic
devices such as Transcutaneous Electrical Nerve Stimulation (TENS) apply
relatively broad pulse durations (50-200 µsec) that aim to excite peripheral
nerves at low amplitude. Macdonald and Coates (1995) examined the effects of
brief duration pulses (≤10 µsec) to produce a painless current of sufficient
amplitude to stimulate the spinal cord.
Sourced from Acticare Website
In
order to produce an action potential in peripheral nerves via electrical
stimulation, the input current must have a low to moderate voltage input and a
high pulse width (Sato & Perl, 1991). TSE works by reducing the pulse width
from 20- 200 to 4 µsec and increasing the Voltage output, therefore increasing
patients pain tolerance and producing little sensation (i.e
tingling) (Macdonald and Coates, 1995). This produces widespread
analgesia when electrodes are placed over the spinal cord. Thus, TSE works by
stimulating the spinal cord with high voltage, low amplitude current directly
to the spinal nerve root.
Electrical pulses employed by TSE can be
delivered at regular intervals in the range of 100 to 50kHz, however most
clinical studies have used a 2-20kHz range (Acticare, 2012). TSE pulses are
typically composed of a biphasic square wave of short duration (≤4ms). This
pulse duration is suggested to be too brief to elicit action potentials in
peripheral nerves at voltages below 150V (peak-to-peak). Furthermore, like TENS
and interferential the short pulse durations of TSE penetrates deeper into the
body resulting in a reduction of skin impedance.
Initially TSE was strictly set at a frequency of 100Hz, however
studies shave shown that the extent of TSE’s analgesic effect is dependent on
its frequency (Acticare, 2012). It has been found in clinical trails that
higher TSE frequencies increased the time to analgesic onset and its overall
affect. For example, at 100 Hz, 40 minutes of application may be
needed to produce analgesia, requiring only 8 minutes at a frequency of 150 kHz
(Li & Bak, 1976).
A
study was conducted by the inventors of TSE sought to determine the
effectiveness of TSE on chronic pain conditions. 100 patients with a variety of
chronic pain causing conditions received TSE to the appropriate spinal nerve
root at a frequency of 600Hz and a pulse width of 4 µsec (square wave),
30min/day for 2 weeks. The patient’s pain levels were assessed via a Visual
Analogue Scale (VAS). Results showed that the TSE treatment reduced pain by 60%
in patients whose pain was of relatively recent origins (2.6 years) (Macdonald
and Coates, 1995). Although, this study’s results showed positive outcomes for
its subjects, more clinical research should be conducted on TSE by independent
researches to decrease bias towards TSE and to compare it to a placebo or other
electrophysiological devices.
In
another double blind, randomized control trial comparing the effects of TSE to
a placebo found different results. Eight subjects with chronic critical limb
ischemia received a placebo treatment for one week, followed by the actual TSE
treatment at a frequency of 2500 Hz and a voltage of 150V to the spinal cord.
McGill Pain Questionnaire measured patient’s pain perception. The results
showed that daily use of TSE did not decrease the subject’s pain or improve
their physical function (Simpson & Ward, 2004). Therefore, suggesting that
TSE did not affect the quality of life for chronic pain patients.
Another
double blind randomized controlled clinical trial which supports the research
conducted by Simpson & Ward, compared TSE to a placebo in chronic low back
pain patients. 58 patients with low back pain were randomly assigned to a
placebo and a TSE receive group and patients were assessed for pain via the
Visual Analogue Scale (VAS). Subjects received the TSE or placebo treatment
twenty minutes per day for 2 weeks. The results showed no difference in mean
pain scores between the TSE and placebo groups (Thompson et.al, 2008).
Therefore, the more recent research conducted by Simpson & Ward and
Thompson et.al suggests that TSE is not effective in treating chronic pain
conditions.
Currently, the evidence on TSE is limited and the
benefits and contraindication of TSE are still unknown. To gain a stronger
understanding of TSE and the benefits it may have in clinical practice, further
research must be conducted.
Macdonald,
A.J.R. & Coates, T.W. (1995). The Discovery of Transcutaneous Spinal
Electroanalgesia and its Relief of Chronic Pain. Physiotherapy. 81 (11): pp. 653-61.
Sato, J.
& Perl, E.R. (1991). Adrenergic excitation of cutaneous pain receptors induced
by peripheral nerve injury. Science. 251 (5001): pp. 1608-10.
Simpson, K. H. & Ward, J. (2008). A Randomised, Double- Blind, Crossover Study of the use of Transcutaneous Spinal Electroanalgesia in Patients with Pain from Chronic Critical Limb Ischemia. Journal of Pain Symptom Management, 28 (5), 511- 519.
Thompson, J. W., Bower, S. & Tyrer, S. P. (2008). A double blind randomized controlled clinical trial on the effect of transcutaneous spinal electroanalgesia (TSE) on low back pain. European Journal of Pain, 12 (3), 371- 377.
