Quantification of nerve tension after nerve repair: correlations with nerve defects and nerve regeneration

This study tested the validity of a quantitative in vitro nerve-tension-measuring technique, by correlating the tension measurements with functional and morphologic assessments of nerve regeneration. Initially, harvested nerves were used in vitro to determine a K value for lateral displacement in this tissue. Next, this value was used to calculate the tension of nerve repair, following 0-, 3-, 6-, and 9-mm resections of nerves in groups of rats. After quantifying the nerve tensions following excision and repair, the authors determined a sciatic function index to evaluate functional recovery and axon diameter in the animals. Functional recovery was significantly impaired in animals with elevated measurable tension (9.04 +/- 0.74 g in a 6-mm defect, 27.76 +/- 8.86 g in a 9-mm defect), compared to animals with no or 3-mm excision and measured tension of 3.3 +/- 1.09 g or less. Increased tension was also associated with a significant decrease in axon diameter. This study succeeded, therefore, in quantitatively relating the elements of measured nerve tension, nerve gaps, functional nerve recovery, and morphologic regeneration. Quantification of nerve tension by lateral displacement in vivo offers a possible solution to clinical management of nerve gaps, when the choice between primary repair and nerve grafting is not a clear one.     

Cavernous nerve regeneration using acellular nerve grafts

INTRODUCTION: The restoration of erectile function following complete transection of nerve tissue during surgery remains challenging. Recently, graft procedures using sural nerve grafts during radical prostatectomy have had favorable outcomes, and this has rekindled interest in the applications of neural repair in a urologic setting. Although nerve repair using autologous donor graft is the gold standard of treatment currently, donor nerve availability and the associated donor site morbidity remain a problem. In this study, we investigated whether an "off-the-shelf" acellular nerve graft would serve as a viable substitute. We examined the capacity of acellular nerve scaffolds to facilitate the regeneration of cavernous nerve in a rodent model. MATERIALS AND METHODS: Acellular nerve matrices, processed from donor rat corporal nerves, were interposed across nerve gaps. A total of 80 adult male Sprague-Dawley rats were divided into four groups. A 0.5-cm segment of cavernosal nerve was excised bilaterally in three of the four groups. In the first group, acellular nerve segments were inserted bilaterally at the defect site. The second group underwent autologous genitofemoral nerve grafts at the same site, and the third group had no repair. The fourth group underwent a sham procedure. Serial cavernosal nerve function assessment was performed using electromyography (EMG) at 1 and 3 months following initial surgery. Histological and immunocytochemical analyses were performed to identify the extent of nerve regeneration. RESULTS: Animals implanted with acellular nerve grafts demonstrated a significant recovery in erectile function when compared with the group that received no repair, both at 1 and 3 months. EMG of the acellular nerve grafts demonstrated adequate intracavernosal pressures by 3 months (87.6% of the normal non-injured nerves). Histologically, the retrieved regenerated nerve grafts demonstrated the presence of host cell infiltration within the nerve sheaths. Immunohistochemically, antibodies specific to axons and Schwann cells demonstrated an increase in nerve regeneration across the grafts over time. No organized nerve regeneration was observed when the cavernous nerve was not repaired. CONCLUSION: These findings show that the use of nerve guidance channel systems allow for accelerated and precise cavernosal nerve regeneration. Acellular nerve grafts represent a viable alternative to fresh autologous grafts in a rodent model of erectile dysfunction.     

End-to-side nerve repair in peripheral nerve injury

In peripheral nerve injury, end-to-side neurorrhaphy has been reported as an alternative in cases that the proximal nerve stump is not accessible. Several hypotheses have been proposed to explain peripheral nerve regeneration after end-to-side neurorrhaphy. Recent evidence suggests that nerve regeneration occurs by collateral sprouting. Although a great number of humoral factors have been identified, molecular mechanism of nerve regeneration after end-to-side neurorrhaphy has not been completely clarified yet. The goal of this technique is to provide satisfactory functional recovery for the recipient nerve, without any deterioration of the donor nerve function. End-to-side technique has been investigated in detail in both experimental and clinical studies. Only a limited number of reported cases in clinical practice, until today, can reveal that end-to-side technique may become a viable means of repairing peripheral nerves in certain clinical situations.     

内脏神经-体神经端侧吻合后神经纤维再生研究

目的 观察大鼠内脏神经-体神经端侧吻合后神经纤维的再生.方法 24只成年SD大鼠随机分为实验组(n=12)和正常对照组(n=12),实验组大鼠通过内脏神经-体神经端侧吻合建立人工体神经-内脏神经反射弧6个月后,在吻合口近端和远端分别截取10 mm的供体神经(L4VR)和受体神经(L6VR),在L6VR延续的盆副交感神经(PPN)和阴部神经(PN)分别截取10 mm的神经.正常对照组大鼠分别取相应节段的L4VR、L6VR、PPN和PN神经.标本经石蜡包埋切片并行甲苯胺蓝染色,比较实验组和对照组大鼠L6VR、PPN、PN神经纤维数量.结果 实验组大鼠横断面可见新生的有髓神经纤维,L4VR、L6VR、PPN和PN的神经纤维数量分别为1602.2±75.7、1037.9±123.6、817.0 ±52.2、510.4±29.1,吻合口远近端神经纤维通过率为64.8%,实验组和对照组大鼠相应的L6VR、PPN、PN神经纤维数目比率分别为70.2%、68.9%和62.2%.结论 大鼠内脏神经-体神经端侧吻合后体神经能够长入并替代内脏神经.     

End-to-side nerve graft for facial nerve reconstruction

Reconstruction of multiple branches of the facial nerve by sural nerve graft using end-to-side nerve suture was performed successfully on a patient with advanced parotid tumor. In this technique, one end of the grafted nerve is sutured with the stump of the facial nerve trunk in an end-to-end manner. Epineural windows are made on the nerve graft, and the distal stumps of the facial nerve branches (temporal, zygomatic, and buccal branches) are sutured with the graft in an end-to-side manner. Functional recovery of all branches and satisfactory facial expression were obtained within 2 years postoperatively. Axonal regeneration through the graft was confirmed by electrodiagnosis. Regeneration through the anastomosis at the stump of the facial nerve trunk using this technique is more efficient than conventional cable grafting, and the length of the nerve required is minimal. This technique may be a useful option for facial nerve reconstruction managing multiple branches.     

跨面神经移植及舌下神经在面瘫中的应用进展

由于感染、外伤、面部肿瘤手术等原因造成的面神经损害,出现面部表情功能丧失和组织营养障碍为主要表现的症候群,引起功能和美学上的并发症,临床称之为面瘫。对于它的治疗,至今还没有统一的治疗方案,各种治疗方法效果不一。而对于神经移植物在国外的研究和使用较多,国内这方面的资料较少,下面就其在面瘫中的应用进展作一综述。     

Proximal nerve elongation vs nerve grafting in repairing segmental nerve defects in rabbits

If segmental nerve defects could be repaired by elongating the proximal or distal segments, nerve grafting might be unnecessary. We elongated a 40-mm proximal segment of an injured median nerve, in the rabbit right forelimb, at a rate of 1 mm/day for 10 days in 10 rabbits and for 15 days in another 10. On the left forelimb of the same rabbits, a 10- for 15-mm segment of the median nerve was removed, and a 10- for 15-mm segment, respectively, of the tibial nerve was grafted in its place. Four months after the initial surgery, nerve conduction velocity (NCV), contractile strength of the flexor digitorum superficialis (FDS), axon count, and axon diameter did not differ significantly between the 10-mm groups but were better in the 15-mm grafted group. Elongating the proximal nerve segment may be an alternative to grafting in repairing segmental defects of less than 10 mm.     

Distal nerve elongation vs nerve grafting in repairing segmental nerve defects in rabbits

Segmental nerve defects have been repaired with nerve grafts. However, regenerating fibers must go through two coaptation sites, and donor site morbidities are inevitable. We elongated the distal nerve segment using a tissue expander and reconnected the nerve. We compared these results with those of nerve grafting. Nerve injury models were created in the median nerves of both forelimbs in 27 rabbits. The right nerve was repaired by elongation, and the left by tibial nerve grafting. The length of the elongation was the same as that of the graft in each animal. Eight rabbits had a 10-mm segment repaired, 9 had a 15-mm segment repaired, and 10 had a 20-mm segment repaired. Evaluated outcomes were nerve conduction velocity, contractile force of the flexor muscle, axons number, and fiber diameter. The elongated and grafted groups did not differ substantially on any outcome. Distal nerve elongation could be an alternative to nerve grafting for repairing large nerve defects.     

Use of nerve conduits in peripheral nerve repair

Studies on nerve conduits for peripheral nerve regeneration have concentrated on the manipulation of various conduit materials to avoid sacrificing native nerve in the clinical situation. With the proliferation of available nerve growth-stimulating factors, the focus is shifting experimentally toward molecular biologic manipulation, with the addition of these materials as substrates within the conduit. The clinical use of conduits has concentrated on the use of autogenous tissue, with a few examples of polyglactin (PGA) mesh and silicone. Ultimately, as yet, conduit material does not seem to have a profound effect on outcome. Substrate manipulation has not yet had clinical application. An important problem that remains, both experimentally and clinically, is overriding the size of the maximal gap that can be bridged successfully, as well as obtaining good functional sensory and motor recovery, compared with the use of nerve grafts. Advances in molecular biology may reveal further details about the nerve growth phenomenon, the precise sequencing of the substrate materials that are effective in promoting nerve growth, and when they should be applied. Advances in chemical engineering may provide additional biologically stable materials that have the ability to integrate growth-enhancing agents or factors into the lumen of the conduit.     

Sciatic nerve palsy following uneventful sciatic nerve block

We describe the loss of function in the sciatic nerve after an uneventful sciatic nerve block using 25 ml of lignocaine 1% with adrenaline 1 in 200 000 in a patient receiving β blocker drugs. Lack of pain on injection and complete regeneration of the nerve after 12 months in a patient with severe peripheral vascular disease led us to postulate ischaemic nerve damage as a mechanism of injury. Adrenaline-induced unopposed α-mediated vasoconstriction in a β-blocked patient is suggested as a possible mechanism of peripheral nerve injury worthy of further investigation.     

The influence of nerve conduits diameter in motor nerve recovery after segmental nerve repair

Many conduits have demonstrated potential to substitute nerve autografts; however, the influence of conduit inner diameter (ID) has never been studied as a separate parameter. This experimental study compared motor recovery after segmental nerve repair with two different ID collagen conduits: 1.5 and 2.0 mm. In addition, the conduits were analyzed in vitro to determine the variations of ID before and after hydration. Thirty rats were divided into three groups: 2.0 mm ID, 1.5 mm ID, and a control group autograft. After 12 weeks, the 1.5 mm ID group demonstrated significant increase in force (P < 0.0001) and weight (P < 0.0001) of the tibialis anterior muscle and better histomorphometry results of the peroneal nerve (P < 0.05) compared to 2.0 mm ID group; nevertheless, autograft results outperformed both conduits (P < 0.0001). Conduits ID were somewhat smaller than advertised, measuring 1.59 ± 0.03 mm and 1.25 ± 0.0 mm. Only the larger conduit showed a 6% increase in ID after hydration, changing to 1.69 ± 0.02 mm. Although autografts perform best, an improvement in motor recovery can be achieved with collagen conduits when a better size match conduit is being used. Minimal changes in collagen conduits ID can be expected after implantation. © 2014 Wiley Periodicals, Inc. Microsurgery 34:646–652, 2014.     

The vascularized saphenous nerve as cross-face nerve graft

Summary The vascular anatomy of the saphenous nerve was studied by cadaver preparation, Indian ink and micropaque injection. A constant vascularized nerve graft with a good pedicle and suitable length for a cross-face anastomosis was found. The vascularized saphenous nerve was used for the first time as a cross-face graft in 8 patients with facial palsy. The Tinel-sign was followed-up and a biopsy of the nerve graft at the time of the muscle transplantation was carried out to compare the morphological results of the vascularized nerve graft with two free sural nerve grafts which were used in two patients at the same time. The functional results are demonstrated.     

骨髓干细胞诱导分化构建组织工程神经

[目的]探讨组织工程化神经修复周围神经缺损的作用。[方法]以DMEM为培养基体外诱导人骨髓基质干细胞分化为雪旺细胞，与细胞外基质及可降解聚乳酸导管构建组织工程化神经；建立坐骨神经缺损10mm的Wistar大鼠动物模型，A组：经诱导骨髓基质干细胞分化雪旺细胞与天然细胞外基质（extra cellular matrix，ECM）凝胶及可降解聚乳酸导管构建组织工程化神经桥接神经缺损；B组：单纯将ECM凝胶注入可降解聚乳酸导管桥接神经缺损；C组：自体神经移植组。术后12周进行神经电生理检测、新生神经组织学观察和轴突计数等检测坐骨神经功能恢复情况。[结果]1．诱导后骨髓基质干细胞呈梭形、胞核大、周围有光晕、突起细长呈纵形排列，GAFP及S-100免疫组织化学染色阳性。动物模型各组经移植术后12周，再生神经已通过缺损区长至神经远端。A组、C组组织学及电生理检测指标均优于B组（PAB=0．021，PBC=0．001），A组与C组无显著性差异（PAC=0．065）；A、B组聚乳酸导管降解吸收明显。[结论]骨髓基质干细胞在体外可诱导分化为雪旺氏细胞，利用其与细胞外基质及可降解聚乳酸导管构建组织工程化神经可以修复周围神经缺损。     

Peripheral nerve block with use of nerve stimulator

The authors describe use of the nerve stimulator in conjunction with a percutaneous exploring needle to achieve peripheral blocks accurately and without injuring the nerve. The nerve stimulator allows accurate nerve blocks without causing paresthesiae and the need for additional anesthetic. This technique decreases the possibility of nerve injury.