TENS for Diabetic Peripheral Neuropathy: Efficacy and Drawbacks

Diabetic peripheral neuropathy (DPN) is an unfortunate complication of long-standing diabetes that causes chronic pain, hyperalgesia, and numbness. Typically worsening at night, DPN interferes with the sleep, daily functioning, and mood of roughly 10% to 20% of patients with diabetes.¹ Treatment options center around pharmacotherapy, with tricyclic antidepressants (TCAs) as first-line, although serotonin-norepinephrine reuptake inhibitors (SNRIs), opiates, opiate-like drugs, and topical medications also are used. Unfortunately, only about 30% to 50% of patients respond to traditional pharmacology.¹ Moreover, troublesome side effects, especially sedation, often lead to discontinuation of treatment.

What other options exist to help alleviate the pain of DPN?

Transcutaneous electrical stimulation (TENS) is one low-cost option that patients can administer at home. What’s the mechanism underlying TENS? What are the contraindications? And, does it really work?

The Mechanism of Action of TENS
TENS has been used as a treatment for DPN since at least the late 1990s. Basically, TENS uses electrodes placed on the skin near the location of pain. Transcutaneous electrical impulses modulate transmission of pain impulses to the brain by inhibiting presynaptic transmission of the dorsal horn of the spinal cord, which directly inhibits nociceptive stimuli. There may also be an element of endogenous pain control, via stimulation of enkephalins, endorphins, and dynorphins.^2,3

TENS is often used as an adjunct to medication. Duration of application ranges from 30 minutes to continuous, and treatment duration ranges from days to months. There are 3 standard settings: conventional; acupuncture-like (high-intensity stimulus, limited by patient tolerance); and pulsed (high-frequency bursts).

Drawbacks and Contraindications
TENS is generally well tolerated, with only minor adverse effects usually reported. Drawbacks of TENS treatment include:

- Skin irritation: occurs in about one-third of patients and is usually related to drying of the electrode gel. Instructing patients on proper use and care of the TENS equipment can minimize this problem.

- Hypersensitivity skin reactions: most often caused by the tape used for applying the electrodes. This can be minimized by using disposable, self-adhesive electrodes, and varying location on repeated application.

- Skin burns: burns may occur if the TENS unit is used incorrectly or for too long; electrodes should not be placed in areas of sensory impairment, where the patient cannot feel a burn developing.

- Contraindicated in patients with pacemakers.

- Contraindicated during pregnancy, since there is a risk of inducing premature labor.

How Well Does TENS work?
Researchers generally agree that TENS can provide sufficient relief of DPN pain, especially during initial use, although its long-term effectiveness is unclear. While some patients may experience enduring benefits, for others the analgesia may occur only during actual stimulation. Although definitive conclusions have been hampered by methodological inconsistencies in study design and small sample size, several recent reviews have looked at the efficacy of TENS for the relief of DPN. Briefly, these reviews have found the following:

- A 2010 report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology found that TENS is “probably effective” for treating diabetic neuropathy, and recommended TENS for consideration in treating DPN (based on a review of 2 prospective matched cohort studies meeting inclusion criteria).⁴

- A 2010 review article in the Journal of Rehabilitation Medicine found that research evidence is consistent and sufficient enough regarding the benefits of TENS to recommend it for use in treating DPN (based on 3 large studies and 1 small study meeting inclusion criteria).⁵

- A 2010 meta-analysis of randomized controlled trials found a significant decrease in mean pain scores at 4 and 6 weeks of treatment, and significant subjective improvement in overall neuropathic pain symptoms at 12 weeks. No TENS-related adverse effects were reported, leading to the conclusion that TENS may be an effective and safe treatment for DPN (based on 3 randomized controlled trials involving 78 patients that met inclusion criteria).⁶

Final Thoughts
Given the disruption in quality of life caused by DPN, TENS may be worth considering. For patients who are able use it appropriately at home, TENS could be an option. After all, it has been around for quite awhile, and is yet another tool you can reach for.

References:

• Lindsay TJ, Rodgers BC, Savath V, Hettinger K. Treating diabetic peripheral neuropathic pain. Am Fam Physician. 2010;82:151-158.
• Basbaum AI, Fields HL. Endogenous pain control mechanisms: review and hypothesis. Ann Neurol. 1978;4:451-462.
• Clement-Jones V, McLoughlin L, Tomlin S, et al. Increased beta-endorphin but not met-enkephalin levels in human cerebrospinal fluid after acupuncture for recurrent pain. Lancet. 1980;2:946-949.
• Dubinsky RM, Miyasaki J. Efficacy of transcutaneous electric nerve stimulation in the treatment of pain in neurologic disorders (an evidence-based review): report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Neurology. 2010;74:173-176.
• Pieber K, Herceg M, Paternostro-Sluga T. Electrotherapy for the treatment of painful diabetic peripheral neuropathy: a review. J Rehabil Med. 2010;42:289–295.
• Jin DM, Yun X, Deng-Feng G, Tie-bin Y. Effect of transcutaneous electrical nerve stimulation on symptomatic diabetic peripheral neuropathy: a meta-analysis of randomized controlled trials. Diabetes Res Clin Pract. 2010;89:10-15.