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Neurophysiological Characterization of Persistent Postthoracotomy Pain

ObjectivesThe postthoracotomy pain syndrome (PTPS) has a prevalence of 30% to 40%. Although intraoperative nerve damage during thoracotomy has been demonstrated, it has not been clearly linked to PTPS and detailed quantitative sensory characterization data have so far not been presented, comparing PTPS and pain-free patients. MethodsNeurophysiological characterization was performed in 17 patients with PTPS and 24 pain-free postthoracotomy patients using a detailed quantitative sensory testing protocol and psychometric questionnaires. ResultsPain and pain-free patients had increased thresholds to tactile detection (P=0.001 and P=0.01) and cool detection (P<0.001 and P<0.01) on the operated side versus the contralateral side. Pain patients also had increased thresholds for warmth detection (P<0.001) and heat pain (P<0.01) on the operated side. The PTPS patients demonstrated increased side-to-side differences for warmth detection (P<0.01), heat pain (P<0.05), and cool detection (P<0.05) thresholds compared with pain-free patients. Pain patients also more frequently experienced cool hyperesthesia (8 of 17 vs. 1 of 24, P<0.01), but no differences were found for pressure pain, temporal summation, or sensory mapping to cool (200 cm2 vs. 76 cm2, P=0.18). Hospital Anxiety and Depression Scale scores were higher for PTPS than for pain-free patients (P<0.01). DiscussionNeurophysiological assessments indicate nerve injury to be common in pain and pain-free patients after thoracotomy. The combination of increased thresholds together with hyperesthesia, suggests consequences of nerve injury to be more pronounced in PTPS patients.