Patients with persistent pain after breast cancer surgery show both delayed and enhanced cortical stimulus processing

Abstract

Emanuel N van den Broeke,1 Marjan de Vries,1 Harry van Goor,3 Kris CP Vissers,1 Clementina M van Rijn,2 Oliver HG Wilder-Smith11Department of Anesthesiology, Pain and Palliative Medicine, Pain and Nociception Neuroscience Research Group, 2Donders Institute for Brain, Cognition and Behavior, 3Department of Surgery, Radboud University Nijmegen Medical Centre, HB Nijmegen, The NetherlandsBackground: Women who undergo breast cancer surgery have a high risk of developing persistent pain. We investigated brain processing of painful stimuli using electroencephalograms (EEG) to identify event-related potentials (ERPs) in patients with persistent pain after breast cancer treatment.Methods: Nineteen patients (eight women with persistent pain, eleven without persistent pain), who were surgically treated more than 1 year previously for breast cancer (mastectomy, lumpectomy, and axillary lymph node dissection) and/or had chemoradiotherapy, were recruited and compared with eleven healthy female volunteers. A block of 20 painful electrical stimuli was applied to the calf, somatopically remote from the initially injured or painful area. Simultaneously an EEG was recorded, and a visual analog scale (VAS) pain rating obtained.Results: In comparison with healthy volunteers, breast cancer treatment without persistent pain is associated with accelerated stimulus processing (reduced P260 latency) and shows a tendency to be less intense (lower P260 amplitude). In comparison to patients without persistent pain, persistent pain after breast cancer treatment is associated with stimulus processing that is both delayed (ie, increased latency of the ERP positivity between 250–310 ms [P260]), and enhanced (ie, enhanced P260 amplitude).Conclusion: These results show that treatment and persistent pain have opposite effects on cortical responsiveness.Keywords: breast cancer surgery, persistent pain, nerve injury, event-related potentials, pain processing