Neurophysiological mechanisms of cancer pain

According to the mechanisms, pain due to cancer can be divided into two categories: Cancer and its metastases chronically affect sensory receptors from deep somatic structures and visceral organs. This permanent stimulation of nociceptors probably additionally involves chemical components (due to inflammation, release of toxic compounds, change in pH and PO2 concentration) with sensitization of the receptors. Cancer directly affecting nerves leads to the destruction of the integrity of afferent nerve fibers and their supporting tissues. This process induces regenerative and degenerative changes in the afferent nociceptive neurons with subsequent changes in their discharge properties (resting activity, response to mechanical and chemical stimulation). Chronic irritation of afferent nociceptive neurons, and possibly chronic stimulation of nociceptors, entails considerable biochemical, morphological, and physiological reactions in the spinal cord. This leads to distortions of the neuronal processing of information from nociceptive afferents. Research on cancer pain, which is essentially research on mechanisms of chronic and recurrent pain in different domains of the body, requires a multidisciplinary approach. It is largely clear what types of questions we have to ask; the techniques for approaching these questions experimentally are available.