NEUROPHYSIOLOGIC ASSESSMENT OF NERVE IMPAIRMENT IN POSTEROLATERAL ANDMUSCLE-SPARING THORACOTOMY

Objective: This study was aimed at analyzing the degree of intercostal nerve impairment in posterolateral and muscle sparing thoracotomy and at correlating the nerve damage to the severity of long-lasting postt horacotomy pain. Methods: Neurophysiologic recordings were performed 1 month after either posterolateral or muscle-sparing thoracotomy to as sess the presence of the superficial abdominal reflexes (mediated in p art by the intercostal nerves), the somatosensory-evoked responses aft er electrical stimulation of the surgical scar, and the electrical thr esholds for tactile and pain sensations of the surgical incision. Resu lts: The patients who underwent a posterolateral thoracotomy showed a higher degree of intercostal nerve impairment than the muscle-sparing thoracotomy patients as revealed by the disappearance of the abdominal reflexes, a larger reduction in amplitude of the somatosensory-evoked potentials, and a larger increase of the sensory thresholds to electr ical stimulation for both tactile perception and pain. In addition, th ese neurophysiologic parameters were highly correlated to the postthor acotomy pain experienced by the patients 1 month after surgery, indica ting a causal role for nerve impairment in the long-lasting postoperat ive pain. Conclusions: This study shows for the first time the pathoph ysiologic differences between posterolateral and muscle-sparing thorac otomy and suggests that the minor long-lasting postthoracotomy pain in muscle-sparing thoracotomy patients is partly due to a minor nerve da mage. In addition, because nerve impairment is responsible for the lon g-lasting neuropathic component of postoperative pain, it is necessary to match specific treatments to the neuropathic pain-generating mecha nisms.