[Anatomy and physiology of chronic pelvic and perineal pain]

To determine the mechanisms involved in the regulation of pelvic and perineal pain.

Description of the anatomical pathways mediating nociceptive transmission and the physiological mechanisms of pain control.

The pelvis and perineum do not have the same innervation. The pelvis is innervated by the sympathetic nervous system, while the perineum is innervated by the somatic nervous system via sacral nerve roots (and the pudendal nerve) and the thoracolumbar sympathetic nervous system. Systems of regulation of nociceptive messages are present at all levels of the nervous system. Two of these systems are essential: one situated in the dorsal horns of the spinal cord (gate control) and another supraspinal system (descending inhibitory system). Via a series of filters and amplifiers, the nociceptive message is integrated and analysed in the cerebral cortex, with interconnections with various areas, especially involving memory and emotion.

Excessive nociceptive stimulation must be clearly distinguished from dysfunction of pain control systems (for example neuropathic pain). The definition of pain: "unpleasant sensory and emotional experience related to a real or potential tissue lesion or described in terms of such a lesion" clearly indicates that not all pain is inevitably related to a persistent and visible cause. Convergence phenomena identified between nerve pathways of the various systems and pelvic organs account for the possible diffusion of visceral nociceptive messages and interactions between organs. A good knowledge of anatomy is essential to understand the patient's description of the pain, and a good knowledge of the modalities of pain control is essential to correctly adapt treatment strategies (drugs, neurostimulation, psycho-behavioural therapy, etc.).