PubMed · 10328244
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R J Schwartzman. 1999. Explaining reflex sympathetic dystrophy.. https://doi.org/10.1001/archneur.56.5.521
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Visceral function is essential for survival. Discreet regions of the human brain controlling visceral function have been postulated from animal studies (Cechetto and Saper [1987] J. Comp. Neurol. 262:27-45) and suspected from lethal cardiac arrythmias (Cechetto [1994] Integr. Physiol. Behv. Sci. 29:362-373). However, these visceral sites remain uncharted in the normal human brain. We used 4-Tesla functional magnetic resonance imaging (fMRI) to identify changes in activity in discrete regions of the human brain previously identified in animal studies to be involved in visceral control. Five male subjects underwent heart rate (HR) and/or blood pressure (BP) altering tests: maximal inspiration (MX), Valsalva's maneuver (VM), and isometric handgrip (HG). Increased neuronal activity was observed during MX, VM, and HG, localized in the insular cortex, in the posterior regions of the thalamus, and in the medial prefrontal cortex. To differentiate special visceral (taste) regions from general visceral (HR, BP) regions in these areas, response to gustatory stimulation was also examined; subjects were administered saline (SAL) and sucrose (SUC) solutions as gustatory stimuli. Gustatory stimulation increased activity in the ventral insular cortex at a more inferior level than the cardiopulmonary stimuli. The observed neural activation is the first demonstration of human brain activity in response to visceral stimulation as measured by fMRI.
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BACKGROUND: Reflex sympathetic dystrophy/complex regional pain syndrome type I (RSD/CRPS I) is a painful neuropathic disorder that may develop as a disproportionate consequence of a trauma affecting the limbs without overt nerve injury. Clinical features are spontaneous pain, hyperalgesia, impairment of motor function, swelling, changes in sweating, and vascular abnormalities. OBJECTIVE: To investigate pathophysiological mechanisms of vascular abnormalities in RSD/CRPS I. DESIGN: Case study. SETTING: Autonomic test laboratory at a university hospital. PARTICIPANTS: A patient with an early stage of RSD/ CRPS I of the upper limb and 2 healthy control subjects. INTERVENTIONS: Cutaneous sympathetic vasoconstrictor innervation was assessed by measuring cutaneous blood flow (laser Doppler flowmetry) and skin temperature (infrared thermometry). To quantify sympathetic vasoconstrictor function, phasic (induced by deep inspiration) and tonic (induced by controlled thermoregulation) sympathetic reflexes were analyzed. Venous norepinephrine levels were determined bilaterally. The same tests were performed in the controls after induction of cutaneous antidromic vasodilation produced by histamine dihydrochloride application. MAIN OUTCOME MEASURE: Sympathetic cutaneous vasoconstrictor function in RSD/CRPS 1. RESULTS: Two weeks after the onset of RSD/CRPS I, skin temperature on the affected side was higher (close to core body temperature) than on the contralateral side at room temperature and during controlled thermoregulation, indicating maximal vasodilation. Phasic and tonic stimulation of cutaneous vasoconstrictor neurons did not induce a decrease of skin blood flow or temperature on the affected side but were normal on the contralateral side. Venous norepinephrine levels were lower on the affected side. Parallel to clinical improvement, loss of vasoconstrictor function completely recovered within weeks. Results of investigations in healthy subjects ruled out the possibility that antidromic vasodilation caused by activation of nociceptive afferents is responsible for the complete depression of sympathetic vasoconstrictor reflexes. CONCLUSIONS: Demonstrated for the first time is a complete functional loss of cutaneous sympathetic vasoconstrictor activity in an early stage of RSD/CRPS I with recovery. The origin of this autonomic dysfunction is in the central nervous system.