Complex Regional Pain Syndrome

Complex regional pain syndrome is the rarest condition in this hub — population studies find roughly 26 new cases per 100,000 people each year, most often in women, most often after a wrist fracture — and the one where early recognition changes the most. It used to go by two older names, reflex sympathetic dystrophy and causalgia, and it still comes in two types: type I, after an injury with no identifiable nerve damage (the large majority), and type II, after a documented nerve injury. Both share the same signature, and this page’s one job is to make that signature recognizable — because CRPS caught in its first months is a very different disease from CRPS found late.

What it looks like

Two features define the picture. First, pain out of proportion: a healed fracture or routine surgery whose pain does not fade on schedule but deepens, spreads beyond the injury, turns burning or squeezing, and makes light touch — a sleeve, a bedsheet — genuinely painful. Second, a limb that visibly changes: color and temperature that differ from the other side, swelling, sweating that is simply wrong, and over time changes in skin, hair, nails, and movement. That visibility matters. If a limb weeks after injury is hurting far more than it should and looks different from its partner, say the letters C-R-P-S to your clinician out loud. The diagnosis is clinical — the Budapest criteria above — and asking the question early is the single highest-value move available.

What’s going on

CRPS is best understood as several systems misfiring together after an injury. The inflammatory response that should stand down after healing keeps running, driven partly by nerve endings themselves releasing inflammatory signals into the limb. The small-nerve regulation of blood vessels and sweat glands goes haywire — hence the color, temperature, and sweating changes. And upstream, the brain reorganizes: imaging studies show the affected limb’s territory in the brain’s sensory map shrinking and blurring, which tracks with the strange feelings patients report — a hand that feels foreign, swollen beyond its true size, hard to locate with eyes closed. None of this is psychological in origin, and none of it is the patient’s doing. It is the nervous system’s plasticity turned against a limb — which is exactly why treatment aims to turn that same plasticity back.

Why the first months matter

CRPS feeds on protection. Guarding the limb is the natural response to pain this severe — and it is the disease’s best friend: disuse worsens the swelling and bone loss, and a limb that stops moving fades further from the brain’s map, which deepens the pain, which invites more guarding. Breaking that spiral early is why time-to-treatment matters more here than in almost any pain condition: treated actively in the first months, many cases improve substantially within the first year, while late diagnoses fight the entrenched version. The message patients most need to hear, and most doubt, is this one: in CRPS, hurt does not equal harm — guarding is the riskier path.

How CRPS is treated today

The cornerstone is rehabilitation that restores movement in graded steps, run by therapists who know this condition. It often begins below the threshold of movement entirely: desensitization to touch, then graded motor imagery — first recognizing left from right hands in photos, then imagining movement — and then mirror therapy, the elegant trick in the figure: the brain watches two healthy hands move, and the shrunken map begins to redraw. Only then does progressive loading of the real limb follow. Everything else supports that arc. Medications are used case by case — nerve-pain agents, short early anti-inflammatory strategies, bone-targeted drugs with promising trial results — with honesty that no single pill has proven itself the answer. Sympathetic nerve blocks can help selected patients, with mixed trial evidence. And for CRPS that resists all of it, neuromodulation has real receipts: spinal cord stimulation proved itself in CRPS in a randomized trial back in 2000, and dorsal root ganglion stimulation — pinpoint stimulation of the nerve cluster serving the painful territory — beat conventional stimulation head-to-head in the ACCURATE trial, making CRPS the condition where next-generation neuromodulation earned its reputation. Psychological support belongs in the plan too — not because CRPS is psychological, but because pain this severe deserves every ally, and fear of movement is a treatment target in its own right.

What’s coming

CRPS research now runs along the neuroimmune frontier — the crosstalk between nerves and immune cells that keeps the limb inflamed — alongside refinements in brain-retraining rehabilitation and stimulation. The mind-and-brain frontier and the pipeline tracker cover the science as it moves.

When to bring in a specialist

Immediately, by this hub’s standards. Suspected CRPS is a reason to reach pain medicine early — for diagnosis by the Budapest criteria, coordinated rehabilitation, and timely escalation if first-line care stalls — rather than after months of watch-and-wait. Finding pain care near you explains how; if a recent injury has left you with pain that is out of proportion in a limb that looks wrong, bring this page’s question to an appointment this month, not this year.