Title Assessment and follow - up of intercostal nerve damage after video - assistedthoracic surgery

Objectives: Chronic pain is a common complication after thoracic surgery. The most important factor appears to be intercostal nerve damage. The purpose of this prospective study was to objectively evaluate intercostal nerve damage associated with post-thoracotomy pain after three surgical procedures using current perception threshold testing. Methods: The 32 patients were classified into three groups: video-assisted thoracic surgery group (n=7), video-assisted mini-thoracotomy with metal retractors group (n=15), and conventional thoracotomy group (n=10). Intercostal nerve function was assessed by a series of 2000-Hz (Aβ fiber), 250-Hz (Aδ fiber), and 5-Hz (C fiber) stimuli using current perception threshold testing (Neurometer CPT/C). The current perception threshold values were measured before and 1, 2, 4, 12, and 24 weeks after surgery. The intensities of ongoing pain were also assessed using a numeric rating scale (0 – 10). Results: Video-assisted thoracic surgery group showed no changes in any current perception threshold values and no residual pain more than 12 weeks after surgery. Video-assisted mini-thoracotomy with metal retractors group and conventional thoracotomy group showed significantly higher current perception threshold values at 2000 Hz 1 week after surgery (p = 0.0013, p = 0.0012, respectively), with pain in approximately 70% of patients 12 weeks after surgery. The correlation between current perception threshold values at 2000 Hz and the intensities of going pain after 4 and 12 weeks surgery was significantly observed (p = 0.03, p = 0.04, respectively). Conclusions: This is the first study that objectively evaluated pain after video-assisted thoracic surgery. The results suggest that the Aβ and Aδ fibers play a significant role in the development of intercostal nerve damage. The current perception threshold values clearly demonstrated that video-assisted thoracic surgery is a less invasive procedure resulting in less post-thoracotomy pain and have some possibilities to objectively evaluate the ongoing pain after surgery. Abstract word count: 300word count: 300