Abstract
We demonstrated the anatomical area of cerebral activation triggered by non-nociceptive stimulation in a single patient with allodynia using functional MRI evaluations, The patient presented with swelling, allodynia and a rise in skin temperature in her right foot after 3 weeks in a cast due to a fracture in the metatarsal bone. Cerebral activation with non-nociceptive stimulus was measured for both the painful right foot and the healthy left foot. The same measurements were carried out 3 months later, after confirming that the allodynia in the patient's right foot had disappeared. Non-nociceptive stimulation to the area with allodynia triggered an increase in activity in the primary and second somatosensory area, inferior parietal lobe, insula, medial prefrontal cortex, anterior cingulate cortex and supplementary motor area, whereas stimulation to the healthy side only resulted in activity in the primary somatosensory area and inferior parietal lobe. Three months later, after the symptoms of allodynia had disappeared, the same stimuli to the right foot showed a decrease in activation of only the primary and second somatosensory area.
Allodynia is secondary to nerve injury or tissue damage. The mechanism of how allodynia is perceived is essentially unknown. In our case the patient presented signs which fit the criteria for CRPS type I. Although these symptoms ceased naturally, the allodynia seen in our patient was common to that of CRPS type I. We believe that our findings are significant for understanding the pathophysiology of allodynia seen in CRPS type I.
