Nerve changes associated with post thoracotomy pain syndrome.

Background: Chronic post-thoracotomy pain (PTPS) is a frequent complication of thoracic operations. Sometimes the pain is excruciating enough to impair activities of daily living (ADL). All thoracic procedures have the potential to cause trauma to the intercostal nerves due to retractor use, chest closure techniques, and or wound healing. In our study, we analyzed the microscopic aspects of the nerves involved in the healing process, to better understand the histopathology of chronic pain.

Material And Methods: 29 patients with PTPS underwent intercostal neurectomy to alleviate the symptoms. Microscopic specimens harvested during the surgeries were sent to our pathology unit for evaluation. The following data regarding the surgical procedures was collected: surgical approach, chest closure type, number of excised nerves, and time interval from previous surgery to neurectomy.

Results: A mean of 2.34±1.11 nerves were excised. Microscopy of the specimens revealed: fibrosis, hyalinization of the epineurium and perineurium, intense hyperemia of the blood capillaries, and interstitial edema. 7 cases presented with myxoid degeneration of epineurium and perineurium. In all the cases, endoneurium, myelin sheaths, and axons were interrupted. The endoneurium showed the presence of hyperemic dilated capillaries. The segmental cytoplasmic vacuolization of Schwann's cells with the total disappearance of axons was also noted. 60% of the examined specimens had intraneural myxoid degeneration, with highly dense irregular connective tissue around nerve fibers.

Conclusions: The pathologic findings in the structure of the intercostal nerves obtained from the patients are indicative of the involvement of the wound healing mechanisms in PTPS. The negative impact of wound healing could be considered a key component in the development of intense chronic pain.