Phrenic and intercostal nerves with rhythmic discharge can promote early nerve regeneration after brachial plexus repair in rats

Exogenous discharge can positively promote nerve repair. We, therefore, hypothesized that endogenous discharges may have similar effects. The phrenic nerve and intercostal nerve, controlled by the respiratory center, can emit regular nerve impulses; therefore these endogenous automatically discharging nerves might promote nerve regeneration. Action potential discharge patterns were examined in the diaphragm, external intercostal and latissimus dorsi muscles of rats. The phrenic and intercostal nerves showed rhythmic clusters of discharge, which were consistent with breathing frequency. From the first to the third intercostal nerves, spontaneous discharge amplitude was gradually increased. There was no obvious rhythmic discharge in the thoracodorsal nerve. Four animal groups were performed in rats as the musculocutaneous nerve cut and repaired was bland control. The other three groups were followed by a side-to-side anastomosis with the phrenic nerve, intercostal nerve and thoracodorsal nerve. Compound muscle action potentials in the biceps muscle innervated by the musculocutaneous nerve were recorded with electrodes. The tetanic forces of ipsilateral and contralateral biceps muscles were detected by a force displacement transducer. Wet muscle weight recovery rate was measured and pathological changes were observed using hematoxylin-eosin staining. The number of nerve fibers was observed using toluidine blue staining and changes in nerve ultrastructure were observed using transmission electron microscopy. The compound muscle action potential amplitude was significantly higher at 1 month after surgery in phrenic and intercostal nerve groups compared with the thoracodorsal nerve and blank control groups. The recovery rate of tetanic tension and wet weight of the right biceps were significantly lower at 2 months after surgery in the phrenic nerve, intercostal nerve, and thoracodorsal nerve groups compared with the negative control group. The number of myelinated axons distal to the coaptation site of the musculocutaneous nerve at 1 month after surgery was significantly higher in phrenic and intercostal nerve groups than in thoracodorsal nerve and negative control groups. These results indicate that endogenous autonomic discharge from phrenic and intercostal nerves can promote nerve regeneration in early stages after brachial plexus injury.

Cryoanalgesia of intercostal nerves following thoracotomy Clinical trial based on animal experiment

BACKGROUND： Cryoanalgesia at -50 ℃ for 90 seconds yields effective pain relief following thoracotomy. In China, -50 ℃ is a common temperature for intercostal cryoanalgesia following thoracotomy. However, experimental results vary. OBJECTIVE： To explore intercostal nerve pathological changes at -70 ℃ for various freezing times by studying canines, and to evaluate long-term clinical efficacy of intercostal nerve cryoanalgesia for postoperative pain relief based on the animal experiments. DESIGN, TIME AND SETTING： A comparative animal study was performed at the Animal Experimental Center of the General Hospital of the People＇s Liberation Army. Based on results from the animal study, a randomized, controlled, clinical trial was performed at the Department of Thoracic Surgery of the General Hospital of the People＇s Liberation Army between October 2006 and October 2008. PARTICIPANTS： A total of 120 patients undergoing posterolateral single incision Iobectomy at the Department of Thoracic Surgery of PLA General Hospital between October 2006 and October 2008 were selected. Nervous system diseases were excluded. METHODS： Animal experiment： 8 anaesthetized, mixed-breed dogs were used. The intercostal nerves （costal bone 6-10） were frozen at -70 ℃ for varying times （30, 60, 90, 120, and 180 seconds）. Clinical study： 120 patients were randomly assigned to 2 groups （n = 60）. In the cryoanalgesia group, the intercostal nerves were frozen prior to chest closure, and 4 costal nerves （1 at incision level, 2 above and below incision, and 1 at drainage tube level） were frozen for 90 seconds at-70 ℃, respectively. Intercostal nerves were not frozen in the control group patients. Dolantin was used to relieve postoperative pain in patients from both groups. MAIN OUTCOME MEASURES： Pathological changes in frozen intercostal nerves were examined at days 1, 10, 30, and 60 following freezing. Following surgery, the degree of postoperative pain in all patients was evaluated by visual analogue scale at days 1,3, 5, 9, 30, 60, 90, and 180. Dolantin doses at days 1, 3, 5, 9 post-surgery and postoperative complications were noted. RESULTS： Nerve damage progressively increased with length of freezing time at -70 ℃, and recovery time from damage was gradually increased. After freezing for 90 seconds, the nerves exhibited obvious histopathological damage, and then completely recovered. In addition, after freezing for 180 seconds, the histopathological changes in nerves were reversible. In the clinical study, visual analogue scale scores were significantly less in the cryoanalgesia group compared with the control group （P 〈 0.01）, which was maintained over 30 days. In the cryoanalgesia group, the mean dolantin dose administered and postoperative complications were significantly reduced compared with the control group （P 〈 0.01）. CONCLUSION： Freezing of the intercostal nerve at -70 ℃ for 90 seconds is a safe and long-term effective method for relieving post-thoracotomy pain.

Use of intercostal nerves for different target neurotization in brachial plexus reconstruction

Intercostal nerve transfer is a valuable procedure in devastating plexopathies. Intercostal nerves are a very good choice for elbow flexion or extension and shoulder abduction when the intraplexus donor nerves are not available. The best results are obtained in obstetric brachial plexus palsy patients, when direct nerve transfer is performed within six months from the injury. Unlike the adult posttraumatic patients after median and ulnar nerve neurotization with intercostal nerves, almost all obstetric brachial plexus palsy patients achieve protective sensation in the hand and some of them achieve active wrist and finger flexion. Use in combination with proper muscles, intercostal nerve transfer can yield adequate power to the paretic upper limb. Reinnervation of native muscles(i.e., latissimus dorsi) should always be sought as they can successfully be transferred later on for further functional restoration.

Nerve transfer helps repair brachial plexus injury by increasing cerebral cortical plasticity

In the treatment of brachial plexus injury, nerves that are functionally less important are transferred onto the distal ends of damaged crucial nerves to help recover neuromuscular function in the target region. For example, intercostal nerves are transferred onto axillary nerves, and accessory nerves are transferred onto suprascapular nerves, the phrenic nerve is transferred onto the musculocutaneous nerves, and the contralateral C7 nerve is transferred onto the median or radial nerves. Nerve transfer has become a major method for reconstructing the brachial plexus after avulsion injury. Many experiments have shown that nerve transfers for treatment of brachial plexus injury can help reconstruct cerebral cortical function and increase cortical plasticity. In this review article, we summarize the recent progress in the use of diverse nerve transfer methods for the repair of brachial plexus injury, and we discuss the impact of nerve transfer on cerebral cortical plasticity after brachial plexus injury.

Evaluation of nerve transfer options for treating total brachial plexus avulsion injury： a retrospective study of 73 participants

Despite recent great progress in diagnosis and microsurgical repair, the prognosis in total brachial plexus-avulsion injury remains unfavorable.Insufficient number of donors and unreasonable use of donor nerves might be key factors. To identify an optimal treatment strategy for this condition, we conducted a retrospective review. Seventy-three patients with total brachial plexus avulsion injury were followed up for an average of 7.3 years. Our analysis demonstrated no significant difference in elbow-flexion recovery between phrenic nerve-transfer （25 cases）, phrenic nerve-graft （19 cases）, intercostal nerve （17 cases）, or contralateral C7-transfer （12 cases） groups. Restoration of shoulder function was attempted through anterior accessory nerve （27 cases）, posterior accessory nerve （10 cases）, intercostal nerve （5 cases）, or accessory ＋ intercostal nerve transfer （31 cases）. Accessory nerve ＋ intercostal nerve transfer was the most effective method. A significantly greater amount of elbow extension was observed in patients with intercostal nerve transfer （25 cases） than in those with contralateral C7 transfer （10 cases）. Recovery of median nerve function was noticeably better for those who received entire contralateral C7 transfer （33 cases） than for those who received partial contralateral C7 transfer （40 cases）. Wrist and finger extension were reconstructed by intercostal nerve transfer （31 cases）. Overall, the recommended surgical treatment for total brachial plexus-avulsion injury is phrenic nerve transfer for elbow flexion, accessory nerve ＋ intercostal nerve transfer for shoulder function, intercostal nerves transfer for elbow extension, entire contralateral C7 transfer for median nerve function, and intercostal nerve transfer for finger extension. The trial was registered at Clinical-Trials.gov （identifier： NCT03166033）.