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
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:
Pain – after injury or surgery – especially chronic intractable pain
Cardiac pacemakers; pregnancy; electrodes over carotid sinus.