Comparison of Peripheral Nerve Regeneration with Side-to-side, End-to-side, and End-to-end Repairs: An Experimental Study

Delayed repair of the facial nerve and its negative impacts on nerve and muscle regeneration

Background

In this experimental protocol, we evaluated the immediate and delayed repair of the buccal branch of the facial nerve (BBFN) with heterologous fibrin biopolymer (HFB) as a coaptation medium and the use of photobiomodulation (PBM), performing functional and histomorphometric analysis of the BBFN and perioral muscles.

Methods

Twenty-eight rats were divided into eight groups using the BBFN bilaterally (the left nerve was used for PBM), namely: G1 - control group, right BBFN (without injury); G2 - control group, left BBFN (without injury + PBM); G3 - Denervated right BBFN (neurotmesis); G4 - Denervated left BBFN (neurotmesis + PBM); G5 - Immediate repair of right BBFN (neurotmesis + HFB); G6 - Immediate repair of left BBFN (neurotmesis + HFB + PBM); G7 - Delayed repair of right BBFN (neurotmesis + HFB); G8 - Delayed repair of left BBFN (neurotmesis + HFB + PBM). Delayed repair occurred after two weeks of denervation. All animals were sacrificed after six weeks postoperatively.

Results

In the parameters of the BBFN, we observed inferior results in the groups with delayed repair, in relation to the groups with immediate repair, with a significant difference (p < 0.05) in the diameter of the nerve fiber, the axon, and the thickness of the myelin sheath of the group with immediate repair with PBM compared to the other experimental groups. In measuring the muscle fiber area, groups G7 (826.4 ± 69.90) and G8 (836.7 ± 96.44) were similar to G5 (882.8 ± 70.51). In the functional analysis, the G7 (4.10 ± 0.07) and G8 (4.12 ± 0.08) groups presented normal parameters.

Conclusion

We demonstrated that delayed repair of BBFN is possible with HFB, but with worse results compared to immediate repair, and that PBM has a positive influence on nerve regeneration results in immediate repair.

Insights on the Choice and Preparation of the Donor Nerve in Corneal Neurotization for Neurotrophic Keratopathy: A Narrative Review

The article introduces neurotrophic keratopathy (NK), a condition resulting from corneal denervation due to various causes of trigeminal nerve dysfunctions. Surgical techniques for corneal neurotization (CN) have evolved, aiming to restore corneal sensitivity. Initially proposed in 1972, modern approaches offer less invasive options. CN can be performed through a direct approach (DCN) directly suturing a sensitive nerve to the affected cornea or indirectly (ICN) through a nerve auto/allograft. Surgical success relies on meticulous donor nerve selection and preparation, often involving multidisciplinary teams. A PubMed research and review of the relevant literature was conducted regarding the surgical approach, emphasizing surgical techniques and the choice of the donor nerve. The latter considers factors like sensory integrity and proximity to the cornea. The most used are the contralateral or ipsilateral supratrochlear (STN), and the supraorbital (SON) and great auricular (GAN) nerves. Regarding the choice of grafts, the most used in the literature are the sural (SN), the lateral antebrachial cutaneous nerve (LABCN), and the GAN nerves. Another promising option is represented by allografts (acellularized nerves from cadavers). The significance of sensory recovery and factors influencing surgical outcomes, including nerve caliber matching and axonal regeneration, are discussed. Future directions emphasize less invasive techniques and the potential of acellular nerve allografts. In conclusion, CN represents a promising avenue in the treatment of NK, offering tailored approaches based on patient history and surgical expertise, with new emerging techniques warranting further exploration through basic science refinements and clinical trials.

Morphofunctional Improvement of the Facial Nerve and Muscles with Repair Using Heterologous Fibrin Biopolymer and Photobiomodulation

Peripheral nerve injuries impair the patient's functional capacity, including those occurring in the facial nerve, which require effective medical treatment. Thus, we investigated the use of heterologous fibrin biopolymer (HFB) in the repair of the buccal branch of the facial nerve (BBFN) associated with photobiomodulation (PBM), using a low-level laser (LLLT), analyzing the effects on axons, muscles facials, and functional recovery. This experimental study used twenty-one rats randomly divided into three groups of seven animals, using the BBFN bilaterally (the left nerve was used for LLLT): Control group-normal and laser (CGn and CGl); Denervated group-normal and laser (DGn and DGl); Experimental Repair Group-normal and laser (ERGn and ERGl). The photobiomodulation protocol began in the immediate postoperative period and continued for 5 weeks with a weekly application. After 6 weeks of the experiment, the BBFN and the perioral muscles were collected. A significant difference (p < 0.05) was observed in nerve fiber diameter (7.10 ± 0.25 µm and 8.00 ± 0.36 µm, respectively) and axon diameter (3.31 ± 0.19 µm and 4.07 ± 0.27 µm, respectively) between ERGn and ERGl. In the area of muscle fibers, ERGl was similar to GC. In the functional analysis, the ERGn and the ERGI (4.38 ± 0.10) and the ERGI (4.56 ± 0.11) showed parameters of normality. We show that HFB and PBM had positive effects on the morphological and functional stimulation of the buccal branch of the facial nerve, being an alternative and favorable for the regeneration of severe injuries.

Outcomes after Anterior Interosseous Nerve to Ulnar Motor Nerve Transfer

Background  Ulnar nerve lesions proximal to the elbow can result in loss of intrinsic muscle function of the hand. The anterior interosseous nerve (AIN) to deep motor branch of the ulnar nerve (DBUN) transfer has been demonstrated to provide intrinsic muscle reinnervation, thereby preventing clawing and improving pinch and grip strength. The purpose of this study was to evaluate the efficacy of the AIN to DBUN transfer in restoring intrinsic muscle function for patients with traumatic ulnar nerve lesions. Methods  We performed a prospective, multi-institutional study of outcomes following AIN to DBUN transfer for high ulnar nerve injuries. Twelve patients were identified, nine of which were enrolled in the study. The mean time from injury to surgery was 15 weeks. Results  At final follow-up (mean postoperative follow-up 18 months + 15.5), clawing was observed in all nine patients with metacarpophalangeal joint hyperextension of the ring finger averaging 8.9 degrees (+ 10.8) and small finger averaging 14.6 degrees (+ 12.5). Grip strength of the affected hand was 27% of the unaffected extremity. Pinch strength of the affected hand was 29% of the unaffected extremity. None of our patients experienced claw prevention after either end-to-end ( n  = 4) or end-to-side ( n  = 5) AIN to DBUN transfer. Conclusion  We conclude that, in traumatic high ulnar nerve injuries, the AIN to DBUN transfer does not provide adequate intrinsic muscle reinnervation to prevent clawing and normalize grip and pinch strength.

Ulnar nerve decompression and transposition with versus without supercharged end-to-side motor nerve transfer for advanced cubital tunnel syndrome: a randomized comparison study

OBJECTIVE

The objective of this prospective randomized study was to compare ulnar nerve decompression and anterior subfascial transposition with versus without supercharged end-to-side anterior interosseous nerve-to-ulnar motor nerve transfer for advanced cubital tunnel syndrome, to describe performing the nerve transfer through a small incision, and to investigate predictive factors for poor recovery following the procedure.

METHODS

Between January 2013 and October 2016, 93 patients were randomly allocated to a study group (n = 45) and a control group (n = 48). Patients in the study group were treated with supercharged motor nerve transfer via a 5-cm incision following decompression and anterior subfascial transposition. Patients in the control group were treated with decompression and anterior subfascial transposition alone. Postoperative pinch strength and compound muscle action potential amplitude (CMAPa) were assessed. Function of the limb was assessed based on the Gabel/Amadio scale. Between-group data were compared, and significance was set at p < 0.05. Potential risk factors were collected from demographic data and disease severity indicators.

RESULTS

At the final follow-up at 2 years, the results of the study group were superior to those of the control group with regard to postoperative pinch strength (75.13% ± 7.65% vs 62.11% ± 6.97%, p < 0.05); CMAPa of the first dorsal interossei (17.17 ± 5.84 mV vs 12.20 ± 4.09 mV, p < 0.01); CMAPa of abductor digiti minimi (11.57 ± 4.04 mV vs 8.43 ± 6.11 mV, p < 0.01); and excellent to good results (0.67 for the study group vs 0.35 for the control group, p < 0.05). Multivariate analysis showed that the advanced age (OR 2.98, 95% CI 2.25-4.10; p = 0.003) in the study group was related to unsatisfactory outcome in the patients.

CONCLUSIONS

In the treatment of advanced cubital tunnel syndrome, additional supercharged end-to-side anterior interosseous nerve-to-ulnar motor nerve transfer may produce a better function of the hand. The authors also found that cases in the elderly were related to unsatisfactory postoperative results for these patients and that they could be informed of the possibility of worsening surgery results.

Effectiveness of Distal Nerve Transfers for Claw Correction With Proximal Ulnar Nerve Lesions

PURPOSE

To evaluate claw deformity correction following anterior interosseous nerve (AIN) end-to-end transfer to the deep motor branch of the ulnar nerve (DMBUN) in high ulnar nerve injuries.

METHODS

Eleven patients were retrospectively evaluated for metacarpophalangeal joint hyperextension and proximal interphalangeal joint extension lag in the fourth and fifth digits following ulnar nerve injury adjacent or proximal to the elbow, who underwent AIN end-to-end transfer to the DMBUN.

RESULTS

Patients underwent surgery an average of 5 months following injury (range, 2-9 months) and were followed for an average of 19 months after surgery (range, 12-30 months). At the last follow-up, clawing was observed in all patients, with proximal interphalangeal joint extension lag averaging 46.8° (SD, ±20°) in the fourth digit and 57.7° (SD, ±12°) in the little finger.

CONCLUSIONS

None of our patients experienced claw correction after AIN end-to-end transfer to the DMBUN.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

The Experience of a Facial Nerve Unit in the Treatment of Patients With Facial Paralysis Following Skull Base Surgery

: The management of facial paralysis following skull base surgery is complex and requires multidisciplinary intervention. This review shows the experience of a facial nerve (FN) unit in a tertiary university referral center. A multidisciplinary approach has led to the breaking of some old treatment paradigms. An overview of five FN scenarios is presented. For each setting a contemporary approach is proposed in contrast to the established approach. 1) For patients with an anatomically preserved FN with no electrical response at the end of surgery for vestibular schwannoma, watchful waiting is usually advocated. In these cases, reinforcement with an interposed nerve graft is recommended. 2) In cases of epineural FN repair, with or without grafting, and a poor expected prognosis, an additional masseter-to-facial transfer is recommended. 3) FN transfer, mainly hypoglossal-to-facial and masseter-to facial, are usually chosen based on the surgeons' preference. The choice should be based on clinical factors. A combination of techniques improves the outcome in selected patients. 4) FN reconstruction following malignant tumors requires a combination of parotid and temporal bone surgery, involving different specialists. This collaboration is not always consistent. Exposure of the mastoid FN is recommended for lesions involving the stylomastoid foramen, as well as intraoperative FN reconstruction. 5) In patients with incomplete facial paralysis and a skull base tumor requiring additional surgery, consider an alternative reinnervation procedure, "take the FN out of the equation" before tumor resection. In summary, to achieve the best results in complex cases of facial paralysis, a multidisciplinary approach is recommended.

Corneal neurotization for neurotrophic keratopathy: Review of surgical techniques and outcomes

Neurotrophic keratopathy is a degenerative disease in which damage to the corneal nerves leads to corneal hypoesthesia. Injuries to neurotrophic corneas are notoriously difficult to treat and have traditionally been approached with supportive management. However, recent progress in the field of corneal neurotization has given new direction for addressing nerve loss directly by stimulating new nerve growth onto the cornea from nearby sensory nerves transferred to the perilimbal region. Herein, we review the surgical techniques utilized in corneal neurotization, including direct transfers and the use of nerve grafts. Considerations in surgical approach, as well as factors that influence prognosis and outcomes of the surgical intervention are also discussed.

Corneal Neurotization and Novel Medical Therapies for Neurotrophic Keratopathy

Purpose of Review

Neurotrophic keratopathy (NK) is a degenerative corneal disease characterized by decreased corneal sensibility and impaired corneal healing. In this article, we review surgical techniques for corneal neurotization (CN) and novel medical therapies for the treatment of NK.

Recent Findings

In recent decades, there has been a paradigm shift in the treatment strategies for NK. New minimally invasive direct and indirect CN approaches have demonstrated efficacy at improving best-corrected visual acuity and central corneal sensation while decreasing surgical morbidity. In addition, several targeted medical therapies, such as recombinant human nerve growth factor (rhNGF), regenerating agents (RGTA), and nicergoline, have shown promise in improving corneal epithelial healing. Of these options, cenegermin (Oxervate®, Dompé), a topical biologic medication, has emerged as an approved medical treatment for moderate to severe NK.

Summary

NK is a challenging condition caused by alterations in corneal nerves, leading to impairment in sensory and trophic function with subsequent breakdown of the cornea. Conventional therapy for NK depends on the severity of disease and focuses primarily on protecting the ocular surface. In recent years, numerous CN techniques and novel medical treatments have been developed that aim to restore proper corneal innervation and promote ocular surface healing. Further studies are needed to better understand the long-term efficacy of these treatment options, their target populations, and the potential synergistic efficacy of combined medical and surgical treatments.

Protective distal side-to-side neurorrhaphy in proximal nerve injury-an experimental study with rats

Background

Side-to-side neurorrhaphy may protect the denervated end organ and preserve the initial connection with proximal stump. We examined the effect of protective side-to-side anastomosis on nerve and end organ regeneration in proximal nerve injury model.

Methods

The left common peroneal nerve of 24 Sprague Dawley rats was proximally transected. In groups B and C, side-to-side neurorrhaphy was performed distally between the peroneal and tibial nerves without (group B) and with (group C) partial donor nerve axotomy inside the epineural window. Group A served as an unprotected control. After 26 weeks, the proximal transection was repaired with end-to-end neurorrhaphy on all animals. Regeneration was followed during 12 weeks with the walk track analysis. Morphometric studies and wet muscle mass calculations were conducted at the end of the follow-up period.

Results

The results of the walk track analysis were significantly better in groups B and C compared to group A. Groups B and C showed significantly higher wet mass ratios of the tibialis anterior and extensor digitorum longus muscle compared to group A. Group C showed significantly higher morphometric values compared to group A. Group B reached higher values of the fibre count, fibre density, and percentage of the fibre area compared to group A.

Conclusions

Protective distal side-to-side neurorrhaphy reduced muscle atrophy and had an improving effect on the morphometric studies and walk track analysis. Distal side-to-side neurorrhaphy does not prevent the regenerating axons to grow from the proximal stump to achieve distal nerve stump.

The role of peripheral nerve surgery in a tissue reinnervation

In modern neuroscience, the most relevant is the study of the problem of reinnervation of tissues after severe injuries. Complete restoration of lost physiological functions is still impossible with lesions of peripheral nerves with the formation of extensive diastasis between their proximal and distal sites. In this case, the standard neurorrhaphy cannot be carried out because of the eruption of the filaments during tension and convergence of the ends. To solve this problem, a technique was developed for autotransplantation of the nerve sections, which is still the gold standard for the reconstruction of extensive nerve defects. However, the presence of significant shortcomings led to the development of the doctrine of the direction of regeneration with the help of conduits. Currently, the use of nerve channels is the most promising technology for peripheral nerve repair after trauma. The most actively developing now is the direction of reinnervation, such as neurotization. Neurotization, in some way, combined all the methods of restoring nerves. The overall goal of all these methods-the restoration of extensive nerve defects-allows them to be combined into a new industry: reinnervating neurosurgery.

Effect of Axonal Trauma on Nerve Regeneration in Side-to-side Neurorrhaphy: An Experimental Study

Background:

Side-to-side (STS) neurorrhaphy can be performed distally to ensure timely end-organ innervation. It leaves the distal end of the injured nerve intact for further reconstruction. Despite encouraging clinical results, only few experimental studies have been published to enhance the regeneration results of the procedure. We examined the influence of different size epineural windows and degree of axonal injury of STS repair on nerve regeneration and donor nerve morbidity.

Methods:

Three clinically relevant repair techniques of the transected common peroneal nerve (CPN) were compared. Group A: 10-mm long epineural STS windows; group B: 2-mm long windows and partial axotomy to the donor tibial nerve; and group C: 2-mm long windows with axotomies to both nerves. Regeneration was followed by the walk track analysis, nerve morphometry, histology, and wet muscle mass calculations.

Results:

The results of the walk track analysis were significantly better in groups B and C compared with group A. The nerve fiber count, total fiber area, fiber density, and percentage of the fiber area values of CPN of the group C were significantly higher when compared with group A. The wet mass ratio of the CPN-innervated anterior tibial muscle was significantly higher in group C compared with group A. The wet mass ratio of the tibial nerve–innervated gastrocnemial muscle was higher in group A compared with the other groups.

Conclusions:

All three variations of the STS repair technique showed nerve regeneration. Deliberate donor nerve axotomy enhanced nerve regeneration. A larger epineural window did not compensate the effect of axonal trauma on nerve regeneration.