Electroacupuncture: an introducti...
Journal of Chinese Medicine • Number 84 • June 2007 1 Electroacupuncture: An introduction and its use for peripheral facial paralysis Electroacupuncture: An introduction and its use for peripheral facial paralysis By: David F Mayor Keywords: Acupuncture, electro- acupuncture, electrotherapy, Bell’s palsy, facial paralysis, neurapraxia (neuropraxia), neurotmesis, nerve, muscle, stages, motor point, denervation, tetany, clinical studies database, superficial needling, point-to-point needling, synkinesis, contracture, exercise, heat Abstract Acupuncture and electrotherapy interface in the practice of electroacupuncture (EA). This article introduces some of the basic concepts and terminology of EA, its advantages and electrical parameters. The aetiology and incidence of peripheral facial paralysis (PFP), its pathology and prognosis are then covered. Conventional treatment of PFP is briefly mentioned, followed by a more detailed discussion of Western electrotherapy for the condition and the evidence for its clinical use. Background information on manual acupuncture (MA) and PFP is given. The literature on EA is reviewed, and EA treatment is then described according to the stage and severity of paralysis. Comparisons between EA and other modalities and combinations with ancillary methods are outlined, and the acupoints and electrical parameters used are analysed in some detail. A final discussion summarises some suggestions for safe and effective treatment. This article is based on the chapter on peripheral motor disorders in the author’s recently published textbook on electroacupuncture,1 together with material from the clinical studies database at wwww.electroacupunctureknowledge.com and an internet trawl of recent research. Note: This article is abridged due to space constraints. The full article at www.jcm.co.uk/JCM Journal/Latest Issue includes a comprehensive table of facial muscles, nerves and corresponding acupuncture points and full references. Electroacupuncture, electrotherapy and peripheral facial paralysis - the background Electroacupuncture: an introduction A cupuncture and electrotherapy interface in the practice of electroacupuncture (EA). Here this is defined as the electrical stimulation of acupuncture points (acupoints) through needles. After the needles are inserted and deqi obtained in the usual way, electricity is passed through pairs of needles to give a continued stimulation, usually for 20-30 minutes. Related treatments include probe or point TENS (pTENS, electrical stimulation using a small diameter handheld probe) and transcutaneous electrical acupoint stimulation (TEAS, stimulation of acupoints via surface electrodes). Another approach is laser acupuncture (LA), the application of low intensity laser light to acupoints, either transcutaneously or through an inserted hollow needle. pTENS, TEAS and non-invasive LA are useful if patients find needles unacceptable, although their effects are not identical. EA is applied at the same points as traditional or manual acupuncture (MA), and has been used for most conditions for which MA is indicated, especially when manual stimulation has not brought a response, or when strong reduction is appropriate (e.g. for severe or acute qi and/or blood stagnation). It is less commonly used in deficiency conditions. Like other forms of electrotherapy, EA is particularly indicated for pain (as in painful obstruction [bi] syndrome), paralysis (both flaccid and spastic) and muscle wasting (as in atrophy disorder [wei syndrome]). It has beneficial effects on microcirculation, inflammation and nerve damage.1 Advantages of EA include: • EA is more effective than MA in some situations, and often potentiates the effects of traditional methods, particularly when strong, continued stimulation is required, as when treating paralysis or some forms of pain.2 • EA can be less time consuming and less demanding of the practitioner than MA, in both training and practice. • Results may in some cases be more rapid,3 and longer lasting.4 • EA may have specific effects on pain, relaxation, circulation and muscle that are different from those of MA.5 • EA is more readily controlled, standardised and objectively measurable than MA. • Non-invasive stimulation methods can also be cost effective for home treatments, perhaps between sessions with a practitioner, although some forms of treatment will require supervision. • EA allows stronger, more continuous stimulation than MA,6 and with less tissue damage.
Journal of Chinese Medicine • Number 84 • June 2007 2 Electroacupuncture: An introduction and its use for peripheral facial paralysis EA differs from MA in several respects (see table 1): The parameters of EA The electric current used in EA has various characteristics: polarity, frequency, amplitude/ intensity, mode, pulse duration, waveform. Polarity (and pulse duration) Current should be biphasic (as in alternating current) rather than monophasic (as in direct current). In other words, current should flow one way and then the other way between the needles, rather than always the same way: Fig 1. (a) Biphasic square wave current (b) Monophasic square wave current. This figure also shows pulse duration. (Adapted from Mayor 2007, with permission.) Frequency Frequency (more accurately, the pulse repetition rate or number of pulses delivered per second) is measured in units of Hertz (Hz). In EA, a ‘low frequency’ (LF) would be approximately 2-4 Hz or pulses per second. A ‘high frequency’ (HF) would be 50-200 Hz. Amplitude/intensity Depending on the type of equipment used, amplitude may be a measure of current or voltage. In EA, maximum amplitude may be of the order of 12 mA (milliampères), or 9 V (volts), but these figures will vary considerably depending on equipment design, and will take account of safety issues for the particular device in question. The strength of sensation experienced by the patient depends on amplitude more than on frequency. Sometimes the level of stimulation is described as ‘sensory’ (feelable), ‘motor’ (resulting in muscle twitching) or ‘noxious’ (frankly painful). Mode Stimulation may be continuous (CW) (as in Fig. 1a above), intermittent (burst), ‘dense-disperse’ (DD, alternating higher and lower frequencies), or otherwise modulated: Fig 2. (a) 2 Hz intermittent (or ‘burst’) current, with an internal frequency of 20 Hz (b) Dense-disperse mode (4/30 Hz DD), repeating every 4 seconds. (Adapted from Mayor 2007, with permission.) MA EA Needle manipulation is brief and intermittent Only ‘low frequency’ is possible (twirling or lifting-thrusting) Strong manipulation risks tissue damage Stimulation is continued for the duration of treatment No limitation to frequency of stimulus (frequency-specific effects occur) Strength of stimulation only limited by patient tolerance Table 1: Some differences between MA and EA Phase duration Pulse duration i(mA) + _ (a) Pulse duration = phase duration i(mA) (b) + _ i 1 sec Interburst duration Burst duration 0.25 sec 5 pulses per burst t (a) i 30 Hz t (b) 4 Hz 2 4 6 8
Journal of Chinese Medicine • Number 84 • June 2007 3 Acupuncture-like stimulation (ALS) LF (high intensity) TENS-like stimulation (TLS) HF (lowintensity) 2-4 Hz 50-200 Hz Pulse duration of around 200 µsec appropriate Pulse duration of 80-100 µsec optimum May be used locally or distally (at extrasegmental or contralateral acupoints, for example) Used locally (for instance at ipsilateral rather than contralateral points) Has segmental and supraspinal neurophysiological effects Has segmental effects (large diameter fibres inhibit pain signals in small diameter fibres in the spine) Releases β-endorphin and Met- enkephalin neurotransmitters in the brain Releases dynorphin in the spinal cord (and other peptides in the brain) Strong stimulation elicits deqi-like sensation High intensity may be uncomfortable LF does not produce muscle spasm at high intensity (in normal muscle) HF may result in uncomfortable tetany (but may also be useful for spasticity) Intermittent pulse trains at high intensity may result in uncomfortable tetany Intermittent pulse trains at low intensity enhance comfort Central effects mean analgesia has slow onset and lasts longer – 30 minutes may suffice for ongoing effect (cumulative) Spinal mechanism means analgesia has rapid onset and does not last long – longer periods of treatment may be necessary No ‘tolerance’ develops from such short treatments Tolerance may develop from longterm use Tends to be used more for chronic pain Tends to be used more for acute pain For deep, aching, throbbing pain For superficial pain associated with inflammation May be helpful for neuralgia and other neuropathic pain (contralateral or distal) May be helpful for neuralgia and other neuropathic pain (local) May benefit peripheral (sensory) nerve injury May be used in hyperaesthesia (especially if cutaneous) May aggravate hyperaesthesia Used for flaccid paralysis (stroke, Bell’s palsy) Used for spasticity Electroacupuncture: An introduction and its use for peripheral facial paralysis Waveform We usually think of waves as curving, rolling, moving forms in nature. In EA, however, square (or rectangular) waves are mostly used, as illustrated here, although some EA devices produce spike or other waveforms. Stimulation ranges It is helpful to consider two main types of stimulation: low frequency (LF)/high intensity (subjectively strong, though still tolerable), and high frequency (HF)/low intensity (subjectively gentle and comfortable). Because of the way these were developed and researched – the former predominantly as EA in China and the latter predominantly as TENS (transcutaneous electrical nerve stimulation) in the West, I have called them ‘acupuncture-like stimulation’ (ALS) and ‘TENS-like stimulation’ (TLS), whether they are applied through needles or surface electrodes. At around 15 Hz, a frequency between the LF and HF ranges, effects may depend on both mechanisms. There is still lack of agreement on whether frequency or intensity is more important in terms of outcome. EA is frequently used in the treatment of peripheral facial paralysis. The discussion that follows illustrates some of the basic principles involved. Cautionary note Electroacupuncture, like any form of electrotherapy, should only be practised following proper instruction and with knowledge of its safety aspects. (Based on Mayor 20071) Table 2: Some differences between ‘acupuncture- like’ and ‘TENS- like’ stimulation