Painful mechanical stimulation evokes activation ofdistinct functional areas in the brain: comparison of normal subjects and two patients with neuropathic pain

Abstract

   We employed functional magneto-resonance imaging to compare the pattern of brain activation evoked by painful and non-painful mechanical stimulation in normal volunteers and patients with neuropathic pain. Stimulation was performed using von Frey filaments. In normal volunteers, painful stimulation caused significant activation in the inferior parietal lobule (area 40), primary motor area (area 4), cingulate gyrus (area 24/31), middle temporal Gyrus (area 21/37), thalamus, and cerebellum. In the non-pain condition, SI, parietal lobule and frontal lobe were activated. In the patients, stimulation in the area of allodynia, in the non-pain condition elicited painful feelings and caused a wider area of activity when compared to the area of activity when the palm of unaffected side was stimulated. The activation was promoted in the frontal and occipital lobes, cingulate gyrus, and cerebellum. These findings suggest that neuropathic pain patients exhibit differences in the pain perception that may reflect chronical activation of the appropriate functional brain areas.