Preliminary findings in the neurophysiological assessment of intercostal nerve injury during thoracotomy

OBJECTIVE: Previous work has suggested that intercostal nerve injury is a major factor in the aetiology of chronic post-thoracotomy pain. The aim of this study was to establish if there was identifiable intercostal nerve injury during thoracotomy. METHODS: Intercostal nerves were stimulated and motor evoked potentials were recorded from intercostal muscles in 13 patients undergoing thoracotomy. Measurements were taken before and after entering the pleural space, after removal of the rib retractor and after intercostal space closure. RESULTS: Intercostal nerves functioned normally before and after entering the pleural space. After the rib retractor was removed, there was a total conduction block in the nerve immediately above the incision in every patient. In the nerves above this, six had a total block, one a partial block and three had normal conduction. There was a total conduction block in the nerve immediately below the incision in all but one patient. Of the nerves below this, four had a total block, two a partial block and three had normal conduction. In the cases of total conduction block, there was either a discrete block at the level of the distal end of the rib retractor or impairment throughout the whole nerve. Intercostal space closure did not injure any previously uninjured nerve. In a solitary patient where rib retraction was not employed, there was no impairment of the intercostal nerves throughout the operation. CONCLUSIONS: This study demonstrates for the first time that intercostal nerve injury occurs routinely due to rib retraction during thoracotomy. We believe that it may be an important step toward understanding the cause of post-thoracotomy neuralgia.