Examination of possible mechanisms by which stimulation of the spinal cord in man relieves pain.

Stimulation of the spinal cord may be very helpful in controlling chronic pain. Traditionally it has been thought that pain control derives from antidromic activation of large-diameter primary afferents in the posterior columns, which inhibits activation of second-order neurons. Evidence against this hypothesis is presented. In addition, it is pointed out that stimulation of the anterolateral quadrant contralateral to the side of pain may require less current for pain control than stimulation with electrodes over the posterior cord. It is suggested that 'frequency-related conduction block' in the spinothalamic tract or in Lissauer's tract may play a role in pain relief. Because of uncertainty about the mechanism it is suggested that the term 'dorsal column stimulation' be replaced by 'spinal axis stimulation'.