Transcutaneous Electrical Nerve Stimulation (TENS)

TENS machine and electrodes.¹

Transcutaneous electrical nerve stimulation (TENS, pronounced ‘tens’) is a common electrotherapy primarily used to treat pain. TENS is a type of electrical stimulation that is delivered using electrical therapy machines connected to electrodes placed on the skin’s surface.

For people with SCI, TENS is used as a treatment option for musculoskeletal pain, neuropathic pain, and spasticity.

It is important to speak with a health provider before using TENS to make sure it is safe and suitable for you and to learn how to use the equipment correctly.

Most machines used for TENS are portable battery-powered devices with adjustable settings like intensity, frequency, and pulse duration. Changing the settings can provide different types of stimulation. The most common types of stimulation are:

• Conventional TENS uses high frequency stimulation to produce sensations of ‘tingling’ or ‘pins and needles’ in areas with normal sensation.
• Acupuncture-like TENS uses low frequency stimulation which may or may not cause muscle twitches in the area.

Electrodes placed on the skin.²

The machine is connected to a set of electrodes by electrical wires (leads). The electrodes may be self-adhesive or applied with conductive gel onto clean, intact skin. Electrodes may be placed near the area of your symptoms or in other areas directed by your health provider.

Once the electrodes and machine have been set up and connected, the intensity is then slowly turned up until it feels ‘strong, but comfortable’ or reaches a set intensity. It should not cause any pain or discomfort.

Your health provider will determine how long the stimulation is used based on the goals of the treatment. After the TENS machine has been safely turned off and the electrodes have been removed, the skin is inspected for any redness or irritation.

Electrical signals are a natural part of how the nervous system works. Signals that are sent along the nerves are relayed in part as electrical impulses. Because the nerves are naturally susceptible to electrical signals, they can be stimulated by electrical therapies like TENS.

TENS stimulates nerve fibres involved in touch. This might work to treat pain and spasticity in several ways:

• TENS may reduce pain by blocking pain signals, so you can feel other sensations instead. This works in the same way as when you rub the skin over a sore area of your body. The unusual ‘tingling’ feeling of the TENS stimulation is sent to the brain instead of pain signals.
• TENS may cause the release of endorphins within the nervous system that may help to reduce pain.
• TENS may affect spasticity by making it less likely that the nerve cells to the muscles (motor neurons) will fire.

TENS can interfere with the function of cardiac pacemakers.⁴

Although there are few reported medical complications caused by using TENS devices, there are many situations in which it could be unsafe to use. The following conditions are some possible restrictions on the use of TENS. Consult a health provider for further safety information.

TENS should not be used in the following situations:

• Near the neck or head of people who have had seizures
• Near implanted medical devices like cardiac pacemakers
• On the abdomen or low back of pregnant women (except during labor and delivery)
• On areas of active cancer (except under medical supervision in palliative care)
• On areas with blood clots, bleeding, or infection
• On the chest of people with major heart problems
• By people who are unable to follow instructions or provide accurate feedback
• Electrodes should not be placed over the eyes, through the head, through the chest, on the front of the neck or genitals, or over damaged skin or open wounds

TENS should be used with caution in the following situations:

• In areas of reduced or absent sensation (such as below the level of injury) – please see above for information on using TENS below the level of injury
• By people prone to autonomic dysreflexia (people with cervical and thoracic injuries)

Learn more in our article on Autonomic Dysreflexia. 

TENS is considered to be a relatively safe and well-tolerated treatment for people who can use it safely (see above for restrictions on using TENS). Serious medical complications from using TENS are rare. However, there are risks and side effects that should be discussed with a health provider before using TENS.

The most common risks and side effects of TENS include:

• Skin discomfort, irritation, or redness near the electrodes
• Allergy to the conductive gel
• Mild electrical burns near the electrodes
• An increase in pain or discomfort
• Mild electrical shocks (from improper use or faulty equipment)

Other less common risks and side effects of TENS include:

• Autonomic reactions, like nausea, light-headedness, fainting, or autonomic dysreflexia
• An increase in spasticity

In some cases, risks and side effects may be caused by improper use of the equipment. For this reason, it is essential to learn to use the equipment from a health provider and to only use TENS according to their direction.

TENS for nerve pain after SCI

Five studies have tested TENS as a treatment for neuropathic pain after SCI, although only three of these studies were suitable to draw conclusions from. These studies provide moderate evidence that TENS is effective for treating neuropathic pain after SCI.

TENS for muscle, bone, and joint pain after SCI

Research has not explored whether TENS is effective for treating musculoskeletal pain after SCI. However, because this type of pain is experienced in areas of normal sensation (above the level of injury), studies done outside of SCI might help provide some guidance about how well this treatment works.

A health provider using TENS on a person’s leg.⁵

Reviews of research studies done in conditions like knee arthritis, general acute pain, and chronic low back pain have shown that TENS may be effective for treating musculoskeletal pain from these conditions. However, much of the research included in these reviews (and for TENS generally) is low quality, making it hard to make strong conclusions about whether TENS works for musculoskeletal pain.

Read more in our article, Pain After Spinal Cord Injury.

TENS for spasticity after SCI

Based on six studies that have tested TENS as a treatment for spasticity after SCI, there is strong evidence that an ongoing program of TENS reduces spasticity after SCI. These studies also show that TENS reduces spasticity even after a single session; although the effects are greater when TENS is used as part of an ongoing program.

Overall, there is moderate evidence that TENS works for neuropathic pain after SCI and strong evidence that TENS works for spasticity after SCI. TENS has not been studied for musculoskeletal pain after SCI, but appears to work for this type of pain in other populations.

TENS appears to be safe to use for most people and is widely available as a low cost treatment option. Until more research is done, it is best to discuss this treatment with your health providers to find out more about if it is a suitable treatment option for you.

For a review of how we assess evidence at SCIRE Community and advice on making decisions, please see SCIRE Community Evidence.

Pain After Spinal Cord Injury

Spasticity

Evidence for “TENS for nerve pain after SCI” is based on the following studies:

[1] Davis R, Lentini R. Transcutaneous nerve stimulation for treatment of pain in patients with spinal cord injury. Surg Neurol 1975;4:100-101.

[2] Bi X, Lv H, Chen BL, Li X, Wang XQ. Effects of transcutaneous electrical nerve stimulation on pain in patients with spinal cord injury: a randomized controlled trial. J Phys Ther Sci 2015;27(1):23-5.

[3] Celik EC, Erhan B, Gunduz B, Lakse E. The effect of low-frequency TENS in the treatment of neuropathic pain in patients with spinal cord injury. Spinal Cord. 2013 Apr;51(4):334-7.

[4] Norrbrink C. Transcutaneous electrical nerve stimulation for treatment of spinal cord injury neuropathic pain. J Rehab Res Dev 2009;46:85-93.

[5] Ozkul C, Kilinc M, Yildirim SA, Topcuoglu EY, Akyuz M. Effects of visual illusion and transcutaneous electrical nerve stimulation on neuropathic pain in patients with spinal cord injury: A randomised controlled cross-over trial. J Back Musculoskelet Rehabil 2015;28:709–19.

Evidence for “TENS for muscle, bone, and joint pain after SCI” is based on the following studies:

[1] Osiri M, Welch V, Brosseau L, Shea B, McGowan J, Tugwell P, Wells G. Transcutaneous electrical nerve stimulation for knee osteoarthritis. Cochrane Database Syst Rev. 2000;(4):CD002823.

[2] Johnson MI, Paley CA, Howe TE, Sluka KA. Transcutaneous electrical nerve stimulation for acute pain. Cochrane Database Syst Rev. 2015 Jun 15;(6):CD006142.

[3] Jauregui JJ, Cherian JJ, Gwam CU, Chughtai M, Mistry JB, Elmallah RK, Harwin SF, Bhave A, Mont MA. A Meta-Analysis of Transcutaneous Electrical Nerve Stimulation for Chronic Low Back Pain. Surg Technol Int. 2016 Apr;28:296-302.

Evidence for “TENS for spasticity after SCI” is based on the following studies:

[1] Oo W. Efficacy of addition of transcutaneous electrical nerve stimulation to standardized physical therapy in subacute spinal spasticity: a randomized controlled trial. Arch Phys Med Rehabil 2014;95:2013-20.

[2] Aydin G, Tomruk S, Keles I, Demir SO, Orkun S. Transcutaneous electrical nerve stimulation versus baclofen in spasticity: clinical and electrophysiologic comparison. Am J Phys Med Rehabil 2005;84(8):584-592.

[3] Possover M, Schurch B, Henle KP. New strategies of pelvic nerves stimulation for recovery of pelvic visceral functions and locomotion in paraplegics. Neurourol Urodyn. 2010 Nov;29(8).

[4] Goulet C, Arsenault AB, Bourbonnais D, Laramee MT, Lepage Y. Effects of transcutaneous electrical nerve stimulation on H-reflex and spinal spasticity. Scand J Rehabil Med 1996;28(3):169-176.

[5] Chung BP, Cheng, BK. Immediate effect of transcutaneous electrical nerve stimulation on spasticity in patients with spinal cord injury. Clinical Rehabilitation, 2010;24:202-210.

[6] van der Salm A, Veltink PH, Ijzerman MJ, Groothuis-Oudshoorn KC, Nene AV, Hermens HJ. Comparison of electric stimulation methods for reduction of triceps surae spasticity in spinal cord injury. Arch Phys Med Rehabil 2006;87(2):222-228.

Other references:

Johnson M. Transcutaneous electrical nerve stimulations (TENS). In: Watson T (Ed). Electrotherapy: Evidence-based Practice Twelfth edition. Edinburgh:Churchill Livingstone; 2008:253-296.

Electrophysical Agents – Contraindications And Precautions: An Evidence-Based Approach To Clinical Decision Making In Physical Therapy. Physiother Can. 2010 Fall;62(5):1-80.*

Cheing GL, Hui-Chan CW. Transcutaneous electrical nerve stimulation: Nonparallel antinociceptive effects on chronic clinical pain and acute experimental pain. Arch Phys Med Rehab 1999;80:305-12.

Jones I, Johnson MI. Transcutaneous electrical nerve stimulation. Contin Educ Anaesth Crit Care Pain 2009; 9(4):130-135.

Somers DL, Clemente FR. The relationship between dorsal horn neurotransmitter content and allodynia in neuropathic rats treated with high-frequency transcutaneous electrical nerve stimulation. Arch Phys Med Rehabil 2003; 84(11):1575-1583.

Johnson M. Transcutaneous Electrical Nerve Stimulation: Mechanisms, Clinical Application and Evidence. Rev Pain. 2007 Aug;1(1):7-11.

Image credits:

1. Tens ©Yeza, CC BY-SA 4.0
2. Electrical Muscle stimulation ©Wisser68, CC BY-SA 3.0
3. Electricity ©Artnadhifa, CC BY 3.0 US
4. St Jude Medical pacemaker with ruler ©Steven Fruitsmaak, CC BY 3.0
5. Day 2 Outpatient PT 013 ©Roger Mommaerts, CC BY-SA 2.0