Transcutaneous Electrical Nerve Stimulation: Mechanisms, Clinical Application and Evidence

Abstract

Transcutaneous electrical nerve stimulation (TENS) is a non-invasive, inexpensive, self-administered technique to relieve pain.There are few side effects and no potential for overdose so patients can titrate the treatment as required.TENS techniques include conventional TENS, acupuncture-like TENS and intense TENS. In general, conventional TENS is used in the first instance.The purpose of conventional TENS is to selectively activate large diameter non-noxious afferents (A-beta) to reduce nociceptor cell activity and sensitization at a segmental level in the central nervous system.Pain relief with conventional TENS is rapid in onset and offset and is maximal when the patient experiences a strong but non-painful paraesthesia beneath the electrodes. Therefore, patients may need to administer TENS throughout the day.Clinical experience suggests that TENS may be beneficial as an adjunct to pharmacotherapy for acute pain although systematic reviews are conflicting. Clinical experience and systematic reviews suggest that TENS is beneficial for chronic pain.

Figures

Figure 1

A standard TENS device

Figure 2a

- Conventional TENS.

Figure 2b

- Acupuncture-like TENS.

Figure 2c

- Intense TENS

Figure 3

Activity in peripheral nociceptive afferents [1] releases excitatory neurotransmitters causing activity in second order nociceptive transmission cells in the central nervous system [2] which leads to pain. Activation of large diameter non-noxious afferents by TENS [3] causes the release of inhibitory neurotransmitters which reduce activity in second order nociceptive transmission cells [4]. The reduction in nociceptive input to the brain results in pain relief [5]. TENS induced activity in non-noxious transmitting pathways in the central nervous system results in a sensation of electrical paraesthesiae [6].