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Currently, there is no single laboratory test for the diagnosis of reflex sympathetic dystrophy (RSD). Therefore, physicians use both subjective (patient history) and objective (physical examination) methods to establish a diagnosis and may include imaging or other tests in order to rule out other conditions.

Patient History

In many cases, the history reveals a recent injury to the site (often minor in nature) or the onset of RSD symptoms following a recent surgical procedure. If a precipitating event can be identified after which the magnitude of signs and symptoms significantly exceeds what would otherwise be expected from the initial event, RSD should be considered as part of the differential diagnosis. Often, the injury may be so slight that the patient does not recall ever having sustained it.

Physical Examination

The physician evaluates signs and symptoms of RSD and verifies those reported by the patient. The doctor may be able to determine the extent of involvement by testing for and observing many of the classic signs of RSD including:

• Range of motion of the affected limb
• Holding up arms above the horizontal plane to evaluate the Tinel sign (when percussing or tapping the area above the nerve suspected to be involved, the patient feels a tingling sensation). If the test is positive, it may be an indication that the origin of the upper extremity RSD is a brachial plexus injury.
• Allodynia and hyperalgesia as a response to various stimuli
• Temperature or color changes
• Changes to hair, nails, or skin
• Evidence of edema

Some patients develop a tendency to guard the affected limb (this is called "guarding" or "bracing" the limb) from any stimulation, including not allowing the physician to examine or manipulate the limb, in order to avoid intense pain. As a result, the doctor may notice neglect in the hygiene and usage of the affected limb.

Imaging Studies

Imaging studies play little role to play in the diagnosis of RSD. They function more as a way of ruling out other medical conditions that may cause similar symptoms: Relevant studies may include:

• X-rays
• Bone Scintigraphy (bone scan) - This test is used to detect increased or decreased areas of bone metabolism and bone changes (e.g., patchy demineralization) in the affected limb. Some physicians may also use bone scans to monitor response to treatment.

• Magnetic Resonance Imaging may be used when other imaging studies are not recommended (e.g., during pregnancy). MRI helps visualize:

  • periarticular marrow edema - swelling caused by increase of fluid around the cartilage of the affected joint
  • joint effusion - increase of fluid within the joint space
  • soft tissue swelling

Sympathetic Nerve Blocks

Some clinicians may perform a sympathetic nerve block in order to determine if the source of the pain is sympathetically-maintained or sympathetically-independent. A local anesthetic or another pain-relieving medication is injected into the sympathetic ganglion (nerve bundle). If the patient experiences pain relief following the block, it means that the pain is sympathetically-maintained and that it may respond to additional sympathetic nerve blocks or sympathectomy (surgical removal of part of a sympathetic nerve) as treatment options.

Thermographic Studies