Sympathetically maintained pain

The sympatic nervous system is an efferent pathway that innervates blood vessels, sweat glands and cardiac muscle. There is considerable evidence that it is also involve in the generation and maintenance of painful conditions. While homeostasis and preservation of thmilieuinterieu are the primary function of this division of the nervous system, under certain poorly understood conditions it may well participate in the preservation of noxious sensory input. Syndromes such as complex regional pain syndrome(CRPS) , reflex sympatic dystrophy (RSD) , and sympatheticallmaintained pain (SMP), SMP was considered to be an inconsistent finding associated with a variety o disorders , including CRPS-I and CRPS-II . Defined as that pain which is maintained or facilitated by some from of sympathetic efferent activity or the action of circulating catecholamines. It is operationally based upon pain relief following systemic or regional sympatholysis (ie, systemic pharmacological treatment or regional sympathetic nervous system blockade). SMP may be an entity in it own right or may be a feature of several different typeof pain disorders. SMP is not an essential component or any one condition. In nonmalignant pain examples of painful conditions where sympathetic maintenance might be found include CRPS-I , CRPS-II , mononeueuropathies, diabetic neuropathy and other painful toxior metabolic neuropathies . In oncologic practice , SMP canbe involved in plexopathies, phantom limb pain, acute herpezoster and postherpetic neuralgia . Yet, SMP is not necessary condition for any of these disorders . However when contributory to the pain, appropriate treatment isdependent upon its recognition and appropriate therapy. Some patients with SM present withpronounced abnormalities in sudomotor and vasomotor function of the affected painful area . Other patients may have minimal physical signs of sympathetic dysfunction and may still have SMP.