Pain catastrophizing and cortical responses in amputees with varying levels of phantom limb pain: a high-density EEG brain-mapping study.

Pain catastrophizing has been associated with phantom limb pain, but so far the cortical processes and the brain regions involved in this relationship have not been investigated. It was therefore tested whether catastrophizing was related to (1) spontaneous pain, (2) somatosensory activity and (3) cortical responses in phantom limb pain patients. The cortical responses were investigated via electroencephalography (EEG) as it has a high temporal resolution which may be ideal for investigating especially the attentional and hypervigilance aspect of catastrophizing to standardized acute stimuli. Eighteen upper limb amputees completed the pain catastrophizing scale. Patients' spontaneous pain levels (worst and average pain, numerical rating scales) and thresholds to electrical stimulation (sensory detection and VRS2: intense but not painful) were determined. Non-painful electrical stimuli were applied to both the affected and non-affected arm, while high-resolution (128 channels) EEG signals were recorded. Catastrophizing accounted for significant amounts of the variance in relation to spontaneous pain, especially worst pain (64.1%), and it was significantly associated with thresholds. At the affected side, catastrophizing was significantly related to the power RMS of the N/P135 dipole located in the area around the secondary somatosensory cortex which has been shown to be associated with arousal and expectations. These findings corroborate the attentional model of pain catastrophizing by indicating that even non-painful stimuli are related to enhanced attention to and negative expectations of stimuli, and they suggest that memory processes may be central to understanding the link between catastrophizing and pain.