Preliminary Investigation of Pain-Related Changes in Cerebral Blood Volume in Patients With Phantom Limb Pain

Abstract

ObjectiveTo investigate changes in the pain network associated with phantom limb pain, magnetic resonance imaging (MRI) was used to measure cerebral blood volume (CBV) in patients who had undergone unilateral arm amputation after electrical injury. DesignCase-controlled exploratory MRI study of CBV via MRI. SettingUniversity hospital. ParticipantsParticipants (N=26) comprised patients with phantom limb pain after unilateral arm amputation (n=10) and healthy, age-matched persons (n=16). InterventionsNot applicable. Main Outcome MeasuresThe intensity of phantom limb pain was measured using the visual analog scale (VAS). Depressive mood was assessed using the Hamilton Depression Rating Scale, and cognitive function was assessed using the Korean version of the Mini-Mental State Examination. Voxel-wise comparisons of relative CBV maps were made between amputees and controls over the entire brain volume. The relationship between individual participant CBV (measured in voxels) and VAS score was also examined. ResultsCompared with control participants, amputees exhibited greater degrees of depression; significantly higher CBV in the bilateral medial frontal area (orbitofrontal cortex [OFC] and pregenual anterior cingulate cortex [pACC]); and significantly lower CBV in the right midcingulate cortex, posterior cingulate cortex, and primary somatosensory cortex. CBV increased in the contralateral and ipsilateral hemispheres of the amputated arm, regardless of the amputation side. This CBV increase in the OFC and pACC was strongly correlated with pain intensity in all amputees. ConclusionsWe observed increased CBV in regions associated with emotion in the cerebral pain network of patients who had undergone unilateral arm amputation after electrical injury. This study suggests that CBV changes were related to neuroplasticity associated with phantom limb pain.