Transcutaneous Electrical Nerve Stimulation

Transcutaneous Electrical Nerve Stimulation (TENS or TNS)

Stimulate nervous system by applying a controlled low voltage electrical pulse to the nervous system via the skin from surface electrodes.

Commonly used. Direct current is used to cause electrical stimulation.

Two types – High frequency – stimulate large afferent fibres  rapid pain relief of short duration.
Low frequency – stimulates large motor nerves  longer duration of pain relief

Mechanisms:
Believed to work via gate control theory of pain  stimulates large diameter afferents  closure of ‘gate’ – not well supported by evidence.
May produce an antidromic blocking of pain impulses
Also may stimulate release of endogenous opiates and may also alter sympathetic tone.

Methods of application:
Electrode placement:

Indications:
Pain – after injury or surgery – especially chronic intractable pain

Contraindications:
Cardiac pacemakers; pregnancy; electrodes over carotid sinus.