Aβ-fiber mediated activation of cingulate cortex as correlate of central post-stroke pain

A patient is presented who suffered a lateral brainstem infarction which selectively abolished pain and temperature sensitivity in the lower right limb. One year later central post-stroke pain had developed in the affected limb with touch and cold allodynia. P40m dipoles calculated from magnetoencephalographic fields after electrical stimulation of both tibial nerves were localized in SI as is seen in normal subjects. However, stimulation of the affected side caused deep pain sensations and elicited a large N80m component, best explained by an additionally active dipole in cingulate cortex. This early co-activation in a limbic structure suggests peripheral AP-fiber mediation and lemniscal projection. Abnormal link to the pain system may be due to sensitization and reorganization above the level of nociceptive deafferentation.