Transcutaneous Electrical Nerve Stimulation for Relieving Pain neuralgia

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					Transcutaneous Electrical Nerve Stimulation for Relieving Pain: Physiological
significance of the 1/f frequency fluctuation.

Professor Kintomo TAKAKURA, Department of Neurosurgery, University of Tokyo,


In recent years, the treatment by electrical stimulation of the nervous system has been
widely practised for relieving pain. Although the surgical method of relieving pain by
cutting the nervous pathway causes the loss of nervous function, the electrical nerve
stimulation can preserve the function and is preferred by patients since it does not give
anxiety or unexpected analgesia. The methods of electrical nerve stimulation include the
deep brain stimulation (DBS) developed by Hosobuchi et al. in which electrical
stimulation is made with electrodes stereotaxically embedded into the central gray
substance (1,2), the spinal cord stimulation (SCS) or dorsal column stimulation (DCS) in
which the spinal dorsal column is electrically stimulated directly or extradurlly (3,5), the
transcutaneous electrical nerve stimulation (TENS) in which the peripheral nerves are
transcutaneously stimulated(6,7).

It is one of the most basic purposes of medical care to relieve pain. It can also remove
the anxiety of the patient. The methods for relieving pain should therefor ebe as
noninvasive as possible and they should not give any anxiety to the patient such as
surgical procedures. Actually when the pain of the patient in the terminal stage of cancer
is treated, most patients and physicians prefer the use of narcotic rather than surgical
treatments. The transcutaneous electrical nerve stimulation, for relieving pain is ideal,
and free from daner, side effect and feelings of anxiety. it has, however, disadvantages
of uncertainty and imperfect for pain relief. This method has gradually been spreading,
and more people have been treated by this method. This paper reviews the
transcutaneous electrical nerve stimulation for relieving pain.


The therapy for relieving pain be electrical nerve stimulation has been applied since the
age of the Roman Empire. It is said that Marcellus de Side in the 2nd century BC
relieved pain by electric shocks using electric rays (8). Pictures which depicted imaginary
scene of tretment at that time was interestingly introduced in a paper of Perdikis (9). In
the oldest remainingpaper written in the Roman age, Scribonium Largas in 46 AD
reported that patients suffering from arthralgia probably due to gout were treated by
torpedo fishes. As for the reason why such a therapy of relieving pain by electric shocks
using electric fishes was practiced, it presumably originated from the experience of long
years that when fishermen happened to be electrically shocked by electric ray fishes, they
felt temporary relief of pain in the case of neuralgia. It is said that the existence of
electric fish is recorded in a picture in a grave erected in the Egyptian age in 2750BC and
the teatment for relieving pain by torpedo fish was transmitted till the middle ages.
Subsequently, the knowledge concerning electricity was clarified, and as soon as the
Leyden jar was invented in 1746, the electric treatment by use of static electricity was
developed by John Wesley, et al in Great Britian. The static electricity was however not
effective for treatment. In the period from 1789 to 1800, Galvani and Volta invented
batteries, and it became possible to feed electric current continuously. Since then,
instruments for treating pain be electrical nerve stimulation were developed. Duchenne
de Boulogne of France published an outstanding paper on the physiology and pathology
of electrical nerve stimulation and its application to treatment in 1855 (10). In the middle
of the 19th century, electrical stimulators for treatment were developed one after another
in Europe and the United States. The system of medical instruments known today was
almost established. Bird, Althaus, et al. in Great Britain and Francis Garratt et al. in the
United States developed the instruments respectively. It was also reported that in the
University Hospital in London, electroanesthesia was applied for tooth extraction, and
was effective for relieving pain in all the 40 cases. Electrical nerve stimulation was
widely used not only for treating toothaches but also pain caused by neuralgia, ischias or
rheumatism and also for relieving paralysis caused by trauma or strikes. Those electrical
therapies practised by the beginning of the 20th century were empiracal. The rationale
for this treatment has gradually been clarified with the development of madern

Why does electrical nerve stimulation relieve pain? Regard to the pain sensation, two
contradictory theories had been put forward. One is the specificity theory that specified
peripheral pain receptors correspond to the sensory centers, and the other is the pattern
theory that neurotransmission was formed to cause pain by strong stimulation, without
specific receptors or centers. Neither of those theories, however, convincingly clarified
the mechanism of pain.

Meanwhile, the gate control theory (11) was proposed by Melzack and Wall (1965).
They hypothesised a group of nerves to suppress the transmission of pain, and that if they
are selectively stimulated, pain can be relieved. As a model of the nervous system for the
transmission and suppression of pain, they proposed a classical theory. The pain
stimulation is entered mainly from small nerve fibers (S) and relayed by T cells in the
spinal cord, to reach the center in the cerebral cortex. In SG (substantia gelatinosa) when
the group of nerves activated by signals entered from large fobers(L), the activity caused
by the stimulation entered from S is suppressed. It is therefore considered that if the
large fiber L is electrically stimulated, the pain is relieved. The pain sensatiion is
important for protecteing the body from external and internal dangers, but if everyminor
stimulation would be conducted to the brain, the man could not tolerate for over
sensation. The animals elaborately use the transmission and suppression of pain, to
create the proper steady state of senses for survival.

 The mechanism of pain conduction in an actual organism is not so simple as the model
proposed by Melzack and Wall. For example, four layer cells in the spinal dorsal column
exist between SG and T cells, and the presence ofmany interneurons has been proposed
by others. Furthermore, the function of the pyramidal tract descending from the barin to
the spinal cord has been postulated, and several correction for the original gate control
theory have been made (12). It is also tried to clarify the pain relieving mechanism based
on a model by using computer simulation. The effect of pain relief, however, contains
large time constants which cannot be interpreted by such a simple element model. For
example, it is often noted that the effect of pain relief appears several minutes after the
start of electrical nerve stimulation and that the effect of pain releif is sustained for hours
even after ceasing the stimulation. It is highly possible that some chemical changes of
neurotransmitters play the role in pain relief by electrical stimulation.

It should be clarified what chemical materials are concerned. Goldstein, et al. clarified
the existence ofopiate receptors in the nervous system. Morphine does not exist in the
human body, but it is surmised that enkephalin and ß-endorphin having similar chemical
structure exist in the portions related with the pain in the brain abd act to relieve pain. It
has been demonstrated that if naloxone, an inhibitor of morphine is added, the pain
relieving effect of acupuncture anesthesia or electrical stimulation of central gray
substance is cancelled. It is therefore considered that these substances are liberated from
some nerve cells or pituitary gland by electrical stimulation, to inhibit the transmission of
pain sensation.

After that Melzack and Wall proposed the gate control theory, the electrical nerve
stimulation for relieving pain has been taken up again from a new viewpoint. Sweet and
Wepsic (14) published a method of electrical stimulation via electrodes inserted into
peripheral nerves for relieving pain, in 1965. Shealy et al. (15, 16) reported a method of
electrical stimulation with electrodes placed to the spinal dorsal column for relieving
pain. Nashold et al (17) stimulated electrically 30 patients suffering from chronic pain,
using similarly embedded electrodes, and reported that the pain caused by any trouble in
the central nervous system could be well relieved. The effect was, however, low for the
chronic arthralgia, or pain due to herniated disc. Since the method of direct application
of electrodes to the surface of the spinal cord for stimulating the spinal dorsal column
requires laminectomy, a simpler method of transcutaneously inserting electrodes into the
epidural space was contrived(18). In this method, each bipolar platinum electrode
enclosed in a tube (1.5 mm dia.) is introduced through a lumbar needle.

The appropriate positions of electrodes are photoscopically placed, and are adjusted by
confirming the effect of pain relief obtained by
electrical stimulation. This method, however, disadvantageously causes liquorrhea
through the electrode tube, and could not be considered as the best way. The electrodes
are therefore transcutaneously inserted into the extradural space recently, to stimulate
indirectly the spinal dorsal column(19 - 24).

As for the effect of pain relief by this method observed by a study group in the United
States(25), 47 cases (68%) out of 71 cases suffering from chronic pain were relieved the
pain at least more than 50%. Lurson. et al. (26) inserted transcutaneously electrodes into
the extradural space to stimulate the dorsal column, 17 cases out of 18 cases suffering
from stubborn pain were alleviated their pains. The effect sustained for several hours
even after the current had been turned off. Although eleven cases of them, while the pain
and tactile senses were lowered, and deep tendon reflexes were intensified, it was
confirmed by autopsy that the spinal cord was not
histologically affected even by electrical stimulation for long time. Monkeys were also
used in the experiment to stimulate electrically the
spinal posterior column (at 100 Hz, for a duration of 0.25 msec, upto 1.0 mA), and it was
observed that the evoked potential in the nucleus ventralis postero lateralis (VPL) and
somato-motor cortex (SMS) by the stimulation of peripheral nerves was recorded. It was
thus presumed that the column stimulation could inhibit the transmission of pain.

The embedding of an electrode and a current receiver like a pace-maker is, however, not
so easy and simple for the patients. Transcutaneous electrical simulators which might be
a revival of the instrument in the 19th century have newly been developed and widely
distributed. It was initially developed for screening the patients who were going to be
mounted with the electrodes to be embedded (27 - 31), but Shealy treated 750 cases
suffering from pain by transcutaneous electrical nerve stimulation and reported that it
was effective for 80% of the patients(6). Eriksson, et al.(32) examined the results of the
long-term application and reported that 55% of 123 cases suffering from chronic pain
desired to continue the treatment for more than 3 months, and 31% of them desired to
continue for more than 2 years, and that the treatment was effective for three quarters of
all the cases. Since the transcutaneous electrical nerve stimulation for relieving pain is
simple in operation and does not give any pain or anxiety to the patient at all, several
kinds of devices have been developed. The pain treated includes not only chronic pain
such as lumbago or neuralgia, but also the pain due to the surgical
interventions(33, 34). Roeser(35) reported that the treatment was also effective for the
muscle pain of sportsmen.

3.   Transcutaneous Electrical Nerve Stimulation = TENS

Although today, a large number of transcutaneous electrical nerve stimulators are being
marketed, they have similar conditions of
stimulation (parameters). The current, voltage, pulse frequency, pulse width, etc. must
be selected to provide a sufficient effect of pain relief within ranges in which patients do
not feel any anxiety or fear by electrical stimulation. Regard to these conditions, the
author's team tried to find a proper range based on the report by Linzer, et al.(36).
Although low current and voltage are not felt, high power obviously increases the effect
of pain relief together with discomfort, anxiety and pain. With repeated stimulation, the
patient becomes accustomed to the current and begins to prefer relatively higher currents
at which higher effect of pain relief is obtained. However, in
general, the range of current is from 5 to 15 mA, and the maximum is about 30 mA. The
range of voltage is from about 10 to 20V. A higher pulse frequency increases
stimulation. About 75% of the patients who admitted the effect of pain relief selected
frequencies of 65 pps or less, and 80%, 120 pps or less. About 10% of patients preferred
high pulse frequencies of 300 to 420 pps, but no patient preferred higher frequencies.
Some patients preferred pulse frequencies of 10 pps or less, but lower frequencies than 1
to 2 pps cause
muscle contraction rather than pain relief. The stimulation at such low frequencies is
therefore used for rehabilitation of the paralysed muscle(20). For the pulse width, 80%
of patients selected a range from 50 to 150us, and 15%, 200 to 350us.

It has been considered that the waveform of electrical stimulation greatly affected the
effect of pain relief, and various models different in
waveform are provided. Waveforms of respective electrical stimulators include unipolar
rectangular, bipolar rectangular, nerve excitation potential, damped vibration wave, etc.
By our experience, even if models different in waveform were used to test the effect of
pain relief, clear difference could not be found. It could not be concluded that any
specific waveform is suitable for pain relief. Further studies are, however, required for
elucidating the best waveform for relief of pain.

If the electrode used for transcutaneous electrical nerve stimulation is too small in the
area of contact with the skin, the local stimulation is felt too strong and unpleasantly.
The size of electrode is required to be at least about 3 cm in diameter, and usually
electrodes of 5 x 4 cm are used. If the skin is dry, the resistance increases and inhibits
smooth conduction of the current. For this reason, paste for the
electrocardiogram is used. Recently, soft polysaccharide electrodes effective for
sufficient conduction of the current and capable of firmly sticking to the skin are used.
The positions of electrodes applied are selected along the line of the peripheral nerves
suffering from pain. The direction of current flow does not seem to affect the effect of
pain relief. It was also tried to apply electrodes along the spinal cord, to allow the spinal
dorsal column to be stimulated. Our experiences revealed that peripheral nerve
stimulation is more effective in relieving pain than spinal cord stimulation.

When the TENS was actually applied to the pain by cancer, herpetic intercostal
neuralgia, spondylosis deformans, etc., about 15% of patients admitted the perfect and
about 30% satisfactory effect of pain relief. There was a dramatic case who had used
narcotic for his cancer pain spreading in the region from the intercostal nerves through
the neck to the upper arms. The pain was relieved by the TENS, without any more
narcotics later at all. On the other hand, the TENS is not effective in some patients. In
general, even if the effect is observed for several days or weeks from the start of
stimulation, the effect becomes weak after a while.

For the treatment is made by electrical nerve stimulation, it is desired to enhance the
effect of pain relief. It is, however, often experienced that when electrical stimulation is
repeated under the same stimulatory conditions such as same pulse frequency, the
stimulation by the monotonous rhythm becomes displeasing. The idea to change the
stimulatory rhythm was introduced in clinical trials. Various marketed devices are
capable to stimulate by variable parameters, for example, by intermittently stopping the
pulse train, by
changing the intensity of current sinusoidally, or by repeating the increase and decrease
of pulse frequency, etc. We intended also to change the pulse frequency at a constant
current. At first, the pulse frequency was changed at random, using random numbers.
By such completely irregular stimulation, sometimes strong stimulation occurs suddenly
and patients rather complain of discomfort by suddenly appeared strong electrical
stimulations. The pulse frequency should be changed always smoothly.

4. Transcutaneous Electrical Nerve Stimulation for Relieving Pain, by Use of the 1/f
Frequency Fluctuation

Our environment comprises of various fluctuations. For instance, we have astronomical
and meteorological fluctuations such as changes of temperature, pressure and the earth's
axis, and vital fluctuations such as changes in electroencephalogram and
electrocardiogram, blood pressure, respiration and circadian rhythm of hormones. All of
these fluctuations are repeated. The features of these various
fluctuations can be analyzed in view of mathematical change, by using correlation
coefficients or power spectra. As an example, the
fluctuation in the mean frequency of classical music recorded is shown in Fig. 2. This
has been obtained by converting analog signals of music to digital signals, obtaining
mean frequencies about every 0.03 seconds and Fourier-transforming them in a time
In this fluctuation, if the frequency is doubled, the power becomes a half, that is, the
power of a frequency is inversely proportional to the frequency. This type of fluctuation
is called 1/f frequency fluctuation. It is positioned between the 1/f0 fluctuation called
white noise and the 1/f2 fluctuation called brown noise. In the 1/f0 fluctuation, the value
at a certain time is quite irrelevant to that of the previous time. The television noise (the
noise appeared after completion of television broadcasting) is an example of this
fluctuation. In the 1/f2
fluctuation, the frequency at a certain time is always strongly affected by the value of the
previous time. Each type of fluctuation is shown in Fig. 3.

Now, let's pay attention to the fluctuations in the organism. First of all, the heart beat of
an adult at rest is approximately 50 to 70 times per minute, but it can be seen
immediately by monitoring, that the heart beat even at rest always fluctuates. If values of
instantaneous heart beat (reciprocal of heart beat period) are sampled at certain time
intervals and are Fourier-transformed, the fluctuation of heart beat can be obtained. It
was found by this method that the fluctuation of heart beat shows 1/f fluctuation(37). A
similar method was applied to the alpha rhythm of an electroencephalogram (EEC).
EEG waves were recorded for 15 minutes, and the alpha rhythm component was taken
out by a band pass filter. It was then converted from analog to digital signals, and the
mean frequencies of every minute were
obtained. The frequencies in a time series were Fourier-transformed, to obtain the
fluctuation power of the alpha rhythm of the
electroencephalogram. The alpha rhythm was thus found to show l/f fluctuation at rest
(Fig. 5B). It has also been known that various fluctuations occurring in organisms are of
1/f. Regard to the significance of 1/f fluctuation in the natural world and in the organism,
a large number of reports have been recently published(38 - 43). Voss (IBM
Laboratories) analyzed the fluctuations of intervals in various kinds of music, and
reported that classical music shows 1/f fluctuation and that rock music shows fluctuation
close to l/f0 (40).

It was considered that when the pulse frequency of electrical nerve stimulation was
changed in the manner preferably and smoothly accepted by the organism, those
changing pattern should be 1/f fluctuation. The 1/f fluctuation rhythm for the electrical
stimulation can be introduced by recording proper classical music into a tape.

Mean frequencies and mean powers (squares of amplitudes) from music are taken out at
certain intervals, and are used as changing frequencies applied for the stimulation. That
is, the changes in the frequencies of sounds in music are converted into pulse frequencies
changing with the lapse of time. As music has scales, pulse frequencies are classified
into several stages. At the same time, the durations of the same frequency are also
classified into several stages. This corresponds to the step-wise durations used in music
such as quarter notes and eighth notes. Actually, the ranges of pulse frequency and
duration felt by volunteers were tested and preset. The pulse frequencies from 20 to 80
pps were classified into 9 stages, and the durations of the same frequency from 0.5 to 4
seconds were
classified into 4 stages. For the irregular stimulation, the change in pulse height (current)
was not used, because an unpleasant feeling was otherwise caused due to abrupt strong
stimulation exceeding a certain range. The current was thus always kept constant. In
view of safety, the maximum current was set to 30 mA, and the voltage was kept in a
range from 20 to 30 V, to feed the peak current. The pulse frequency and duration were
controlled according to the 1/f fluctuation rhythm.

The music used was quiet and popular classical music such as "Fantasy of harmony"
composed by Vivaldi, "Pastoral" by Beethoven, and also popular songs, etc. The cassette
tape had both the signals for electrical stimulation and music recorded concurrently, to
allow the music to be listened to, considering the psychological effect for the patients.
Since a time lag of about 1 second is present between the hearing and the cutaneous
sensation, the stimulation signals were recorded at positions ahead of those for music by
about 0.8 second.
At the beginning of this treatment, it was intended to give electrical stimulations in
smoothly changing rhythm and a music tape was used just as a means for generating the
rhythm. Since a tape for recording stimulation rhythm was made based on music, it was
decided later to allow the individual patients to listen to the music when they wish,
concurrently to provide a psychological effect of tranquilization. Various kinds of music
were recorded into the tapes so that each patient could select the music he likes.


On the effects of pain relief confirmed by using marketed transcutaneous electric nerve
stimulators, Long(27) and Shealy, et al.(30) already reported. Long reported that out of
197 cases suffering from chronic lumbago, pain due to lumbar and cervical spondylosis
or disc hernias,78 cases (40%) could be almost perfectly relieved of pain. We treated the
patients suffering from the diseases as shown
in Table 1, using a marketed stimulator and a 1/f fluctuation stimulator.

Table 1 The causes of pain in the patients treated by percutaneous electrical nerve stimulation
(regular and 1/f fluctuated irregular pulse stimulation)

The causes of pain were trauma (injured cervical injury, etc.), inflammation mainly
caused by herpes, cancer, lumbago & backpain, spondylosis deformans, etc. To express
the effect of treatment against pain, each patient who had been stimulated electrically for
10 minutes or more was questioned as to the degree of pain relief. A case where pain
was perfectly alleviated was expressed by 0, a case where no effect was obtained, by 10,
and a case where the pain was alleviated to a half, by 5. The results are shown in Table

Table 2 The effects of transcutaneous electrical nerve stimulation (TENS). The degree of pain after
treatment is expressed by the numbers 0 to 10. The degree of pain before treatment is set as number
10. Thus, the complete relief of pain is expressed as 0 and no relief of pain as 10. Pain relief is
compared between patients treated with regular pulse and 1/f irregular pulse, with or without
listening to music.

In the 60 cases who were stimulated at a constant and regular frequency, the average
degree of pain relief after treatment was 6.5 ± 1.8. If the cases with the pain reduced by
50% or more are considered as effective cases, the effectiveness rate was 35%. On the
contrary, in 91 cases who were stimulated electrically with the 1/f fluctuation without
music, the average degree of pain after treatment was 4.8 ±2.4, and the effectiveness rate
was 70.3%. In the 69 cases who were electrically stimulated with the 1/f fluctuation
while listening
to music, the average degree of pain after treatment was 4.7 ±2.2, and the effectiveness
rate was 73.9%. Thus, the effects of pain relief by 1/f electrical stimulation were found
to be more pronounced than those treated by regular electric stimulation.

As for the psychological effect of music, there was no significant difference, but about
70% of patients desired to listen to music concurrently. It should especially be noted that
even many of the old patients desired to listen to music. Furthermore, all the patients
who used both stimulators of constant frequency and 1/f fluctuation, preferred the use of
the 1/f stimulator. After a treatment period of 30 minutes, more than 80% of patients
desired to continue the treatment. It was often experienced that the effect of pain relief
continued several hours even after turning off the current to finish the treatment of
electrical nerve stimulation. The rate of cases admitted the
presence of the post-effect was 36% of all the patients treated by constant frequency
stimulationand 54% of all the patients treated by 1/f
For evaluating the degree of pain relief objectively instead of the subjective judgement of
patients, hypoalgesia was measured before and
after treatment by the two-point discrimination and a pressure gauge, and the alpha
rhythm of electroencephalograms was also analyzed. In the two-point discrimination, the
skin was touched by an instrument like vernier calipers at two points, to measure the
value at which the two points were felt as one point. The values were obtained by
measuring lengthwise and crosswise at forehead, chest wall and the region of pain, and
the average value obtained after treatment was divided by that obtained before treatment,
to get a change ratio. For measurement at pressure points, an instrument like a spring
balance was used to press the three points mentioned above, and the values of the
pressure at which the patient felt pain were averaged. Then, similarly the change ratio of
the values before and after the treatment was obtained. The current values required for
treating the patients effectively are shown in comparison in Table 3. Comparing the
results of constant frequency stimulation and 1/f stimulation before and after treatment,
the ratio of the two-point discrimination was 1.17 : 1.44, and that with the pressure gauge
was 1.08 : 1.23. As can be seen in these ratios, the 1/f stimulation induced hypoalgesia
more effectively. The ratio of current values effective for treatment was 2.76 mA : 1.46
mA, showing that the 1/f stimulation provided effect at a lower current value.

Table 3 The effects of electrical nerve stimulation by needle electrodes applied to the peripheral
nerve for pain relief. The effects of regular and 1/f fluctuated irregular pulse stimuli are compared.
The two point discrimination test value was determined by average multiplied value of two
directions measured at the forehead, chest wall and local area of the pain.
The number in the table is the value after treatment divided by the value before treatment. The
pressure ismeasured at the point of pain induction and the value
after treatment is divided also by the value before treatment. The current indicates the average peak
value (mA) of the stimulation for relieving pain.

It is well known that at rest, alpha rhythm appears in the EEG. This status is analyzed as
a bird's eye view of EEG in Fig. 4. The Figure shows the state of a person at rest, the
state where he listened to his favorite music, and the state when he heard unpleasant
noise of 1 kHz square waves.

 Fig 4. Bird's eye view of the EEG of a person during the stages of rest, tranquil state at listening to
quiet music and unpleasant state at hearing of intolerably loud noise (1kHz. rectangular noise). Left:
                     All EEG. Right: Extracted a-rhythm through band pass filter

The left part of the figure shows the analysis of an entire EEG, and the right side, only
alpha rhythm extracted by a filter. As can be seen from the Figure, at rest and during
listening to music, alpha rhythm appeared, but alpha rhythm disappeared during hearing
unpleasant noise. It is known that in a patient suffering from pain, alpha rhythm
disappears and beta rhythm predominates while he feels strong pain, and that alpha
rhythm appears while the pain is relieved(46).

A case suffering pain due to fracture of her patella is presented. The EEG of the patient
was Fourier-analysed. While the pain was felt, the pattern of the alpha rhythm was close
to 1/f0 fluctuation (Fig 5A). The patient was treated by electrical stimulation with the 1/f
fluctuation. As a result, as shown in Fig 5B, the alpha rhythm showed the pattern of the
1/f fluctuation.
Fig 5A. The power spectrum of EEG alph-rhythm of a patient with pain in the fractured patella.
              The pattern of her alpha-rhythm is composed of 1/f0 fluctuation.
Fig. 5B The power spectrum of EEG Q rhythm of the same patient during treatment (percutaneous
electrical nerve stimulation using 1/f irregular pulse). The pattern of the a-rhythm is composed of 1/f
fluctuation and local pain has subsided.

It was further revealed that when the pain was restored after turning off the current, the
alpha rhythm returned again to the pattern of the l/f0 fluctuation. The analysis of alpha
rhythm is surmised to be worthwhile to evaluate objective relief of pain in future.


The transcutaneous electrical nerve stimulation for relieving pain has been historically
overviewed. The noninvasive therapy should be undertaken in the initial stage for
treatment of pain. Needless to say, the essential treatment of pain is due to cure the
primary disease causing the pain. It is, however, required to find out methods of pain
relief for treating the pain not allowing the cause to be eliminated, like the pain of a
patient in the terminal stage of cancer. It is obvious that the causes of pain are so
variable. In specific pains, excellent methods with dramatic pain relieving effects without
destroying the nervous function are being developed, such as the neurovascular
decompression (Jannetta, 47)) for trigeminal neuralgia. Further studies are required in
coming years, to acquire proper and effective
methods for treating respective kinds of pain. For the transcutaneous electrical nerve
stimulation to relieve pain, future problems include the identification of most effective
points to be stimulated, automatic identification of such regions and, establishment of
objective evaluation of pain relief. New ideas governing the homeostasis of nervous
functions including neuro-electro-physiological and neuro-chemical-transmitting
functions should be introduced for development of comprehensive pain relief system
based on the feedback of these physiological changes.


The author would like to thank Dr. Yukio Kosngi, Prof. Jun Ikebe, Mr. Makolo Suzuki,
Mr. Takao Takahashi, and Prof. Tushimitsu Musha, of Tokyo Institute of Technology,
for their cooperation concerning new researches in this paper.


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*The references only written in Japanese are omitted (blank numbers).
For any question or opinion on this article, please write directly to:
Kintomo Takakura
Dept. of Neurosurgery,
Faculty of Medicine,
University of Tokyo,
3-1, Hongo 7-chome,
Bunkyo-ku, Tokyo