The target article discusses various aspects of the
relationship between the sympathetic system and pain. To this
end, the patients under study are divided into three groups.
In the first group, called “reflex sympathetic dystrophy”
(RSD), the syndrome can be characterized by a triad of autonomic,
motor, and sensory symptoms, which occur in a distally generalized
distribution. The pain is typically felt deeply and diffusely, has an
orthostatic component, and is suppressed by the ischemia test. Under
those circumstances, the pain is likely to respond to sympatholytic
interventions. In a second group, called “sympathetically
maintained pain” (SMP) syndrome, the principal symptoms are
spontaneous pain, which is felt superficially and has no orthostatic
component, and allodynia. These symptoms, typically confined to the
zone of a lesioned nerve, may also be relieved by sympathetic blocks.
Since the characteristics of the pain differ between RSD and SMP, the
underlying kind of sympathetic–sensory coupling may also vary
between these cases. A very small third group of patients exhibits
symptoms of both RSD and SMP. The dependence or independence of
pain on sympathetic function reported in most published studies seems
to be questionable because the degree of technical success of the
block remains uncertain. Therefore, pain should not be reported as
sympathetic function independent until the criteria for a complete
sympathetic block have been established and satisfied.
Local Anesthetic Sympathectomy Restores fMRI
Cortical Maps in CRPS I after Upper Extremity
Stellate Blockade: A Prospective Case Study