Sensory testing in patients with postthoracotomy pain syndrome: Part 1: mirror-image sensory dysfunction

Mirror-image sensory dysfunction (MISD) has not been systematically characterized in persistent postoperative pain.

The presence of MISD was evaluated with standardized stimuli, in preoperative patients scheduled for a thoracotomy (n = 14) and in patients with postthoracotomy pain syndrome [PTPS (n = 14)]. The primary outcome was investigation of the areas of sensory dysfunction, evaluated twice by dynamic sensory mapping with metal rollers and a brush.

In PTPS patients, sensory dysfunction was present on the surgical side, and in 12 of 14 patients MISD was demonstrated. The total areas of sensory dysfunction [median (interquartile range)] were: day 1, 500 (289 to 636) cm and 60 (0 to 379) cm on the surgical and nonsurgical side (P < 0.005), respectively; and day 2, 355 (266 to 697) cm and 81 (0 to 202) cm on the surgical and nonsurgical side (P < 0.0002), respectively. Magnitudes of areas on the surgical side, respective of the nonsurgical side, did not significantly differ between the 2 days of investigation (P > 0.5). The agreement between test-retest assessments was fair to excellent on the surgical side but poor on the nonsurgical side. None of the PTPS patients experienced mirror pain.

MISD is a common finding in PTPS patients and deserves further study involving mechanism and clinical implications.