[Neurosurgical treatments for pain]

Pain represents the most frequent symptom faced by general practitioners and is associated with 60% of neurological troubles. Pain consists in a conscious, subjective, unpleasant and protective sensory experience transmitted by thermoalgic pathways in the central nervous system (nociceptive pain). Lesioning of peripheral or central sensory pathways can also generate pain associated with hypoesthesia (phantom or neuropathic pain). Since the 1920's, neurosurgeons have attempted to alleviate nociceptive and neuropathic chronic pain by interrupting (irreversible interruptive techniques) thermoalgic fibers (neurotomies, rhizotomies, cordotomies, tractotomies, thalamotomies, cingulotomies). Some of them (neurotomies, rhizotomies) are still used today when all medications have failed. They can provide immediate and tremendous pain relief like in trigeminal neuralgia. However, the technique, when not sufficiently selective, can generate a neuropathic pain and then a short-lating pain relief. Increasing knowledge on pathophysiological mechanisms of pain allowed surgery to interfere with the functioning of the sensory circuits without lesioning and to modulate neuronal activity in order to reduce pain (neuromodulation). Non-lesioning modulating techniques (then reversible) appeared (deep brain stimulation, epidural spinal cord or motor cortex stimulation, intrathecal infusion, radiosurgery) and are currently applied to efficiently alleviate neuropathic pain.