A rarely performed neurological operation to relieve intractable PAIN. The thalamic tracts of the SPINAL CORD contain the nerve-fibres that signal pain. They travel from the source of the pain – in an organ or tissue such as skin or bone – via the cord to the brain stem and cortex (see BRAIN) where the individual becomes ‘conscious’ of the pain. The operation aims to sever these tracts within the medulla oblongata of the brain.