Hemisensory disturbances in patients with complex regional pain syndrome

Sensory disturbances often spread beyond the site of injury in complex regional pain syndrome (CRPS) but whether this applies equally to CRPS I and II, or changes across the course of the disease, is unknown. Establishing this is important, because different symptom profiles in CRPS I and II, or in acute vs chronic CRPS, might infer different pathophysiology and treatment approaches. To explore these questions, sensory disturbances were assessed in the limbs and forehead of 71 patients with CRPS I and 33 patients with CRPS II. Pain had persisted up to 12 months in 32 patients, for 13 to 36 months in 29 patients, and for longer than this in 43 patients. Patients with CRPS I were more likely to be female, and pain was more likely to be present in an additional limb, than patients with CRPS II. Conversely, pain was more likely to be associated with sensory deficits and allodynia in patients with CRPS II than CRPS I. Nevertheless, heightened sensitivity, allodynia, and/or hyperalgesia to mechanical and thermal stimuli were detected in a hemisensory distribution ipsilateral to the affected limb in both forms of CRPS. Some of these hemisensory disturbances strengthened with chronicity of pain. These findings suggest that heightened excitability of nociceptive pathways in CRPS spreads to hemisensory convergence points in the brainstem or higher brain centres, possibly in association with compromised pain controls. The similarity of symptom profiles in chronic CRPS I and II implies shared mechanisms despite different triggers.