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


CONCLUSIONS
These results show that treatment and persistent pain have opposite effects on cortical responsiveness.
Department of Anesthesiology, Pain and Palliative Medicine, Pain and Nociception Neuroscience Research Group, HB Nijmegen, The Netherlands.
Emanuel N
EN
van den Broeke
Marjan
M
de Vries
Harry
H
van Goor
Kris Cp
KC
Vissers
Clementina M
CM
van Rijn
Oliver Hg
OH
Wilder-Smith