Nerve Suture Research Articles

The facial nerve in the presence of a head and neck neoplasm: assessment and outcome after surgical management.

The face is the mirror of personality. Facial expression is the most important part of verbal and nonverbal communication. Patients with head and neck neoplasm and facial palsy are more stigmatized by the latter than by the tumor itself. Facial nerve reconstruction in such a patient is a great challenge. This review gives an overview of the assessment of facial palsy, surgical reconstruction, and postoperative treatment. MRI, CT, and electromyography are indispensable tools in the assessment of preoperative facial palsy in patients with head and neck neoplasm. When part of the facial nerve has to be sacrificed during surgery, the best functional results are achieved with direct facial nerve suture, interposition graft, or by a hypoglossal-facial nerve interposition jump anastomosis. The latter is the best choice when the reanimation is planned between 6 months and 2 years after tumor surgery. In any case, the eye is best rehabilitated with upper lid loading. Temporalis muscle transposition gives fast and good results for the restoration of the corner of the mouth after radical surgery. Reanimation by free muscle transfer for head and neck cancer patients is rarely indicated. Botulinum toxin treatment is an excellent postoperative aid for refining the result; the optimal modality of postoperative physiotherapy is still unclear. Surgical reanimation of the face in head and neck patients has reached a high standard. Strategies to decrease misdirected reinnervation after nerve suture have to be established in clinical practice for further improvement of facial rehabilitation.

Alleviated tension at the repair site enhances functional regeneration: the effect of full range of motion mobilization on the regeneration of peripheral nerves--histologic, electrophysiologic, and functional results in a rat model.

In the clinical management of combined tendon and nerve injuries, competing treatment strategies are well known. The effect of mobilization on the functional regeneration of peripheral nerves remains controversial. This study sought to determine the effect of full range of motion mobilization on nerve repair by using tubular segmental nerve splinting to block movement, and thereby variable tension, at the nerve repair site. In 96 rats, the right sciatic nerve was transected midthigh and coapted immediately microsurgically. The groups used in the study were as follows: group N, epineural nerve repair; group T, segmental tubular nerve splinting with fixed in situ tension at the nerve suture site,allowing segmental movement only; group TN, segmental tubular nerve splinting with alleviated in situ tension at the nerve suture site, allowing segmental movement only; and group TM, segmental tubular nerve splinting without fixed in situ tension at the nerve suture site, allowing movement of the nerve suture site. Full range of motion of the lower limbs was ensured by passive motion of hind limbs once a week after functional testing. Blinded histologic, immunohistochemical, and electrophysiologic assessment and 12 postoperative weekly function tests were carried out. Functional and electrophysiologic results were significantly better in group TN, by segmental tubular nerve splinting with alleviated in situ tension at the nerve repair site, mainly because of less scar formation and enhanced endoneural angiogenesis at the nerve suture segment. Full range of motion mobilization may impede functional nerve recovery by significant endoneural collagenization and decreased angiogenesis at the nerve suture segment. Complete alleviation of in situ (pathophysiologic) tension at the nerve suture site seems to improve functional peripheral nerve regeneration.

Fiber arrangements of nerves belonging to ventral and dorsal divisions in the proximal region of the brachial plexus: a study using fluorescence of DiI and DiO in adult rats.

The motor and sensory fiber arrangements in the proximal region of the spinal nerves are important for understanding the relationship of the peripheral nerves to neuron distribution. On the other hand, the fiber arrangements are also important for the treatment of peripheral nerve grafting. We studied the fiber arrangements of two divisions (ventral and dorsal) in the proximal region of the brachial plexus and the fiber arrangements of the lateral cutaneous rami in Th7 and Th8 intercostal nerves in adult rats with a method using the fluorescent pigments DiI and DiO. Results showed that fiber arrangements belonging to the two divisions have a specific separate distribution in the distal region. However, this specific separate distribution form was absent in the proximal region of the spinal nerves in the plexus. Fiber arrangements of the lateral cutaneous ramus in the anterior branches of the thoracic nerves (intercostal nerves) were also observed in comparison with those in the brachial plexus by the same method. In the intercostal nerves, fibers of the lateral cutaneous ramus were distributed in the dorsal portion from distal to proximal. These results suggest that there are two types of fiber arrangement in the proximal regions of the spinal nerves: a ventrodorsal distributional type, comprising intercostal nerves and the dorsal branches of the spinal nerves; and a mixed type, comprising the anterior branches of the cervical and brachial (and perhaps lumbar) plexuses. On the other hand, fibers of the lateral cutaneous rami in the intercostal nerves were distributed on the dorsal part of the nerves. These results of fiber arrangement analysis for the intercostal nerves may offer an opportunity to improve the effect of treatments using peripheral nerve grafting and suturing in the brachial and lumbar plexus with intercostal nerves.

Late results after nerve transplantation on the upper extremities

The purpose of this retrospective study was to determine the influence of the type of injury, the time elapsed after the injury, the blood supply to the operation area, the size of the graft, and the applied treatment method on the late results. In the study period from 1985 through 2000, nerve transplantations had been performed in 281 patients. There were 204 men and 77 women. Reconstructions were applied on the median nerve in 59 patients, ulnar nerve in 48, median and ulnar nerves in 23, radial nerve in ten, and digital nerves in 141 patients. 188 patients presented for late follow-up (66.9%). Evaluation was made according to the Highet scheme. In patients with median nerve transplantation M(3) or better results were seen in 69%, with M(3) being 45.2%. S(3) or better was observed in 64.3%, with S(3) being 47.6%. In patients after ulnar nerve transplantation M(3) or better result was achieved in 56.8%, M(3) being 19%. S(3) or better result was seen in 32.4%, S(3) being 27%. In patients who underwent median and ulnar nerve transplantations M(3) or better result was seen in 36.8%, M(3) being 26.3%. S(3) was in 42.1%, while S(4) did not occur. In patients after radial nerve transplantation M(3) or better effect resulted in 87.5%, M(3) being 12.5%. In patients with digital nerve transplantation S(3) or better result occurred in 57.4 %, S(3) being 47.6%. The best result can be achieved with nerve suturing, performed as an optimum from all aspects. However, as far as the surgical technique is concerned, results of using interfascicular grafts are more advantageous than epineural nerve suture based on compromises. In ideal circumstances, transplantation of a nerve graft less than 2 cm is of the same value as a good primary suture. If a nerve graft is longer than 2 cm, and negative local factors are accumulating due to the type of injury, late results will gradually deteriorating. The final outcome definitely depends on the patient's age and the time elapsed from the injury to the operation.

Peripheral and Spinal Motor Reorganization after Nerve Injury and Repair

Functional recovery after peripheral nerve injury depends on the amount as well as on the accuracy of reinnervation by regenerative axons. In this study, the rat sciatic nerve was subjected to crush injury or complete transection repaired by either (1) straight nerve suture, (2) crossed nerve suture of tibial and peroneal fascicles, or (3) silicone tubulization leaving a gap of 4 mm. The compound muscle action potentials (CMAP) of gastrocnemius, tibialis anterior and plantar muscles were recorded 90 days post operation to assess functional reinnervation and Fast Blue, Fluoro Gold and DiI were applied to the nerve branches projecting into these muscles to quantify morphological reinnervation. The CMAP amplitude achieved in gastrocnemius, tibialis anterior and plantar muscles was higher after nerve crush (86%, 82%, 65% of control) than after any surgical nerve repair (straight suture: 49%, 53%, 32%; crossed suture: 56%, 50%, 31%; silicone tube: 42%, 44%, 25%). The total number of labeled motoneurons, however, did not significantly differ between groups (control: 1238 +/- 82, crush: 1048 +/- 49, straight suture: 1175 +/- 106, crossed suture: 1085 +/- 84, silicone tube: 1250 +/- 182). The volume occupied by labeled motoneurons within the spinal cord was larger after surgical nerve repair than in crush or normal control animals, and fewer neurons showed abnormal multiple projections after crush (2.5%) or straight suture (2.2%) than following crossed suture (5%) or silicone tube (6%). In conclusion, nerve repair with a silicone tube leaving a short gap does not increase accuracy of reinnervation.

Transplantation of primary satellite cells improves properties of reinnervated skeletal muscles.

Skeletal muscle demonstrates a force deficit after repair of injured peripheral nerves. We tested the hypothesis that transplantation of satellite cells into reinnervated rabbit tibialis anterior (TA) muscles improves their properties. Adult rabbits underwent transection and immediate suture of the common peroneal nerve. In order to provide an environment favorable for cell transplantation, TA were then made to degenerate by cardiotoxin injection, either immediately or after a 2-month delay, which is sufficient for muscle reinnervation. In both cases, the injured TA were transplanted with cultured satellite cells 5 days after induction of muscle degeneration. When cells were transferred immediately after nerve repair, drastic morphological and functional muscle alterations were observed. However, when the muscles were allowed to become reinnervated before cell transplantation, muscles were heavier and developed a significantly higher maximal force compared to denervated-reinnervated muscles. Thus, application of the cell therapy protocol improved properties of denervated muscles only when they were allowed to become innervated. These results, which represent the application of cell therapy to improve force recovery of reinnervated muscles, will be of significant interest in certain clinical contexts, particularly after immediate or delayed muscle reinnervation.

Neuromuscular rehabilitation by treadmill running or electrical stimulation after peripheral nerve injury and repair.

Numerous studies have been devoted to the regeneration of the motor pathway toward a denervated muscle after nerve injury. However, the regeneration of sensory muscle endings after repair by self-anastomosis are little studied. In previous electrophysiological studies, our laboratory showed that the functional characteristics of tibialis anterior muscle afferents are differentially affected after injury and repair of the peroneal nerve with and without chronic electrostimulation. The present study focuses on the axonal regeneration of mechano- (fibers I and II) and metabosensitive (fibers III and IV) muscle afferents by evaluating the recovery of their response to different test agents after nerve injury and repair by self-anastomosis during 10 wk of treadmill running (LSR). Data were compared with control animals (C), animals with nerve lesion and suture (LS), and animals with lesion, suture, and chronic muscle rehabilitation by electrostimulation (LSE) with a biphasic current modulated in pulse duration and frequency, eliciting a pattern mimicking the activity delivered by the nerve to the muscle. Compared with the C group, results indicated that 1) muscle weight was smaller in LS and LSR groups, 2) the fatigue index was greater in the LS group and smaller in the LSE group, 3) metabosensibility remained altered in the LS and LSE groups, and 4) mechanosensitivity presented a large increase of the activation pattern in the LS and LSE groups. Our data indicated that chronic muscle electrostimulation partially favors the recovery of muscle properties (i.e., muscle weight and twitch response were close to the C group) and that rehabilitation by treadmill running also efficiently induced a better functional muscle afferent recovery (i.e., the discharge pattern was similar to the C group). The effectiveness of the chronic electromyostimulation and the treadmill exercise on afferent recovery is discussed with regard to parameters listed above.

Nerve welding using CO2 laser

Although microsurgical techniques of nerve suture are now widely practiced, the prognosis is not always satisfactory. In many cases, conventional suture repair results in neuroma formation and a fibrotic reaction that is detrimental to nerve regeneration. Studies on the peripheral nerves in rats and other species have helped in the development of laser-assisted nerve anastomosis. In the field of otorhinolaryngology, facial nerve anastomosis, particularly in difficult-to-reach sites, may need such a non-contact sutureless laser technique to overcome the difficulties of other conventional methods. In this study, 40 rat sciatic nerves were sharply cut then immediately repaired using 100 mW CO2 laser with or without solder (two groups). The rats were followed up to record the functional studies, electrophysiological, and histopathological findings of the two groups (A and B). It was found that laser repair is faster and simpler with more stability and more function with the use of a solder (Group B). The long-term results of this laser nerve welding study are comparable to results of conventional methods in the literature.

Effects of Immediate and Delayed Facial–Facial Nerve Suture on Rat Facial Muscle

Objective—To investigate regeneration of the mimic musculature after delayed facial nerve repair.Materials and Method—In 30 rats the facial nerve on the right side was resected and immediately repaired with an end-to-end anastomosis. The entire levator labii muscle was removed on the right side and histochemically and morphometrically analyzed at 7, 14, 21, 28, 90 and 180 days after immediate nerve repair. In a further 20 rats, reinnervation was performed after 4 weeks in a further operation and the muscle was assessed at 14, 28, 90 and 180 days. Seven muscles of four normal rats were used as controls.Results—Three muscle fiber types could be identified by comparative histochemical analysis of two enzymes of succinate dehydrogenase (SDH) and m-ATPase: oxidative glycolytic (FOG) fibers, fast glycolytic (FG) fibers and intermediate muscle fibers that were designated SDH-INT. The number of fibers and the frequency distribution of single-fiber cross-sectional areas were determined for each type of fiber. No significant difference in the cross-sectional area of all fiber types was noted after 180 days when comparing immediate and delayed end-to-end sutures. In contrast, comparison of the fiber-type composition showed a significant increase in the number of FG fibers in the delayed suture, at the expense of FOG fibers. After immediate reinnervation the muscle approximately attained its natural fiber-type composition, whereas after delayed reinnervation the muscle showed an overall loss of oxidative capacity and differentiation towards phasic activity.Conclusion—Changes in fiber-type composition following delayed nerve suture are irreversible and have specific effects on the precise function of the muscle. Immediate nerve repair improves axonal reinnervation.

End-to-side nerve suture in clinical practice.

The phenomenon of lateral sprouting of axons into an end-to-side sutured recipient nerve is well documented. The exact nature, however, still needs further investigation. Since 1996, we have been continuously involved in primate research as well as using this end-to-side nerve suture (ETSNS) method in clinical practice. Fifty-six patients with a variety of conditions, ranging from brachial plexus avulsion to digital nerve lesions, have been operated. From our experience, it seems that the best results achieved are proximal motor re-innervation (e.g. biceps) and distal sensory re-innervation (e.g. volar skin of the hand). The discussion will cover various aspects for ETSNS in the human patient, such as indications, parameters, technique, and the importance of rehabilitation. ETSNS restores function in conditions previously difficult to operate, and may replace nerve grafting in many instances. It provides an additional method in our armamentarium in peripheral nerve surgery.

Re-innervation of M. biceps by end-to-side nerve suture.

End-to-side nerve suture (ETSNS) is a viable option to re-innervate a paralysed biceps muscle. The host or donor nerve could be any of the adjacent large nerves including the brachial plexus. It is important to adhere to certain principles when performing ETSNS, e.g. epineural window only, suture line without tension, the recipient nerve should not "kink" in any way and complete immobilisation for at least three weeks. The earlier this ETSNS is done after injury the better the outcome. Patient co-operation and motivation is of the utmost importance. The post-operative rehabilitation programme is essential to "awaken" and strengthen the dormant muscle. Our results are based on five patients. Good elbow flexion, i.e. biceps contraction can be regained after ETSNS of, for example, the musculo-cutaneous nerve into an appropriate viable host nerve.

Pre-degenerated nerve shows enhanced regeneration after incremental elongation in rats

Following nerve degeneration, we investigated effects of linear elongation on subsequent nerve regeneration in a total of 92 Wistar rats (weight 380–430 g). The nerve was ligated at the midthigh and then elongated incrementally by a total of 15 mm by leg lengthening at a rate of 3 or 5 mm/day. Seven days after initiation of nerve elongation, the external fixator was removed and normal leg length was restored with internal fixation. Then a 10 mm nerve segment at the ligature site was excised, and the nerve was repaired with sutures (group D). At 2, 4, 6, and 8 weeks after nerve suturing, we examined transverse semi-thin nerve sections compared with group I (severed and repaired after leg lengthening without a nerve ligature) and control group (severed and repaired without leg lengthening). After lengthening at 3 mm/day, nerve regeneration in group D was enhanced at 4 weeks. After lengthening at 5 mm/day, nerve regeneration in group D also was enhanced at 6 and 8 weeks. Pre-degenerated nerve showed better regeneration after suturing than intact nerve. Elongation holds promise as an alternative to nerve grafting in treatment of nerve injury.

End-to-side neurorrhaphy of sensory nerves

One century passed before end-to-side neurorrhaphy was rediscovered, and now it finds more frequent use in clinical practice. Experimental studies have improved our understanding of the underlying mechanism and its potential. However, still discussed is whether reinnervation by end-to-side neurorrhaphy works as well in sensory nerves as in motor nerves. The digital nerves are sensory nerves and therefore an ideal model to investigate this question. Two cases of successful sensory reinnervation by end-to-side nerve suture are reported. We began to use end-to-side nerve repair clinically in 1995 and have used it for motor or sensory reinnervation in a total of 13 cases. In two patients primary nerve repair using end-to-side neurorrhaphy was performed in digital avulsion injuries. In one patient the avulsed ulnar nerve of the thumb was sutured end-to-side to the median nerve; in the other the ulnar digital nerve of the ring finger had been destroyed over a distance of 20 mm, and the distal stump was joined end-to-side to the radial nerve of the same finger. Sensory recovery was obtained in both patients. The static two-point discrimination was 3.0 mm, and dynamic two-point discrimination was 2–3 mm for the reinnervated finger compared to 2 mm for static and dynamic two-point discrimination in the adjacent "donor" finger. The sensation of the finger supplied by the "donor nerve" was not altered in relation to the corresponding contralateral finger site. Excellent sensory reinnervation is possible through an end-to-side nerve suture. Proximal avulsion, missing proximal nerve stumps, partial recovery, and prevention of nerve grafts are good indications for resensitization using end-to-side neurorrhaphy. No harm to the donor nerve is expected. Preference should be given to donor nerves that supply skin areas near to the anesthetic area.

End-to-side neurorrhaphy of motor nerves: reinnervation of free muscle transplants—first clinical application

End-to-side neurorrhaphy may offer a practical solution in limited cases of nerve reconstruction when no donor nerve or nerve transfer is available for direct end-to-end nerve suture, or when extremely long distances for nerve regeneration cause irreversible atrophy of the targets. We report our experience with the successful clinical use of a completely new technique of end-to-side neurorrhaphy for motor reinnervation of free functional muscle transplants. Since 1995 we have used end-to-side nerve repair for motor or sensory reinnervation in 13 cases. A free functional muscle graft was reinnervated by an end-to-side neurorrhaphy in four patients after tumor resection (two myocutaneous latissimus dorsi flaps), Volkmann's contracture (one myocutaneous latissimus dorsi flap), and in a long-standing brachial plexus lesion (one gracilis muscle flap). All four patients showed reinnervation of their muscle graft through the end-to-side nerve suture site. Two functional muscle grafts to the upper extremity had positive outcome of M3–M4 for elbow and finger extension in one case, and M4 for finger flexion in one case more than 2 years after transplantation. The transplant in the brachial plexus lesion is too early for a final functional result. One patient had a M3 for knee extension 8 months postoperatively. In the clinical cases there was no downgrading of the muscle functions supplied by the "donor" nerve. Good and clinically relevant reinnervation of a functional muscle graft is possible through an end-to-side nerve suture. Proximal avulsion, missing proximal nerve stumps, partial recovery, shortening of long distances for nerve regeneration, and prevention of long nerve grafts in proximal lesions are good indications for reinnervation of a functional muscle transplant by end-to-side neurorrhaphy without harm to the donor nerve. Donor nerves supplying synergists should be preferred.

Endoscopic dissection of recipient facial nerve for vascularized muscle transfer in the treatment of facial paralysis

In order to prepare recipient facial nerve branches for neurovascular muscle, transfer in the treatment of facial paralysis, endoscopic facial nerve dissection was employed. Under endoscopy recipient facial nerve branches innervating the zygomaticus major muscle were successfully dissected. A stab incision was sufficient for nerve suture with the donor nerve. This method is preferable for young or female patients in whom conventional cheek incisions should be avoided.

Promoting nerve regeneration through long gaps using a small nerve tissue graft

Background If nerve tissue is capable of inducing regeneration, as suggested by the neurotropism theory, then even small pieces of nerve tissue should have the potential to induce nerve regeneration. Therefore, long gaps might presumably be bridged via the neurotrophic potential of small pieces of nerve tissue grafted into the middle of the nerve gap. It is necessary to confirm the validity of the neurotropism theory and to also explore the potential usefulness of small nerve grafting through long gaps. Methods A small piece of nerve tissue was grafted into a silicone tube bridging a relatively long nerve gap in an attempt to promote nerve regeneration. A 15-mm gap was created in the left sciatic nerve of 31 Wistar rats (8 weeks of age). The experimental groups included one with nonvascularized nerve tissue grafted into a silicone tube with no distal nerve suturing (NV-A), another with vascularized nerve tissue grafted into a silicone tube with no distal nerve suturing (V-A), a third group with nonvascularized nerve tissue grafted into a silicone tube with distal nerve suturing (NV-P), a fourth group with vascularized nerve tissue grafted into a silicone tube with distal nerve suturing (V-P), and a group with no nerve segment grafted into the silicone tube (control). Electrophysiologic and histologic examinations were performed 10 weeks after the operation. Results No regeneration was obtained in the control group. Nerve regeneration was evident at the proximal end of the tube in the NV-A, V-A, NV-P, and V-P groups, and at the distal end in the NV-P and V-P groups. The degree of distal regeneration was extremely slight in the NV-A and V-A groups. An electrophysiologic examination performed in the NV-P and V-P groups revealed better results in the latter group. Conclusion Small nerve grafts are capable of inducing nerve regeneration even over a long nerve gap, by grafting nerve tissue into the middle of the lesion using a silicone tube.

Adjacent and spontaneous neurotization after distal digital replantation in children.

In an exclusively pediatric population, this retrospective study examined the functional and aesthetic results after distal replantation without nerve suture. The aim was to demonstrate, in the child, the presence of spontaneous nervous regeneration resulting in a fingertip pulp with discriminatory sensation. Eight amputations in eight children with a mean age of 9 years and 2 months on the day of the accident were reviewed. The cases were managed by a single surgeon over a period of 8 years and were collected from two different hand centers. The patients were then examined by a different surgeon, and the data were collected. Sensibility was evaluated using the Weber, Semmes-Weinstein, and wrinkle tests. The results were excellent, with mean values of 4.6 mm for the Weber test, 3.3 for the Semmes-Weinstein test, and a positive wrinkle test in all subjects. All patients thus recovered discriminatory sensation with minimal aesthetic sequelae. The usual factors adversely affecting the results of the replantation (ischemic time, level and mechanism of the amputation, and quality of the venous return) were examined, but no statistical analysis was performed because of the small sample size. This study demonstrates the presence of the clinical phenomenon of adjacent neurotization in the absence of nerve repair. It thus confirms that children are excellent candidates for replantation of the distal extremities, even when nerve suture is not performed.

Motoneuron adaptability to new motor tasks following two types of facial-facial anastomosis in cats.

The ability of the facial motor system to adapt to a new motor function was studied in alert cats after unilateral transection, 180 degrees rotation and suture of the zygomatic nerve, or transection and cross-anastomosis of the proximal stump of the buccal nerve to the distal stump of the zygomatic nerve. These procedures induced reinnervation of the orbicularis oculi (OO) muscle by different OO- or mouth-related facial motoneurons. Eyelid movements and the electromyographic activity of the OO muscle were recorded up to 1 year following the two types of anastomosis. Animals with a zygomatic nerve rotation recovered spontaneous and reflex responses, but with evident deficits in eyelid kinematics, i.e. the proper regional distribution of OO motor units was disorganized by zygomatic nerve rotation and resuture, producing a permanent defect in eyelid motor performance. Following buccal-zygomatic anastomosis, the electrical activity of the OO muscle was recovered after 6-7 weeks, but air puff-, flash- and tone-evoked reflex blinks never reached the control values on the operated side. Electromyographic OO activities and lid movements corresponding to licking and deglutition activities were observed on the operated side in buccal-zygomatic anastomosed animals up to 1 year following surgery. Mouth-related facial motoneurons did not readapt their discharges to the kinetic, timing and oscillatory properties of OO muscle fibres. A significant hyper-reflexia was observed following both types of nerve repair in response to air puffs, but not to light flashes or tones. In conclusion, adult mammal facial premotor circuits maintain their motor programmes when motoneurons are induced to reinnervate a foreign muscle, or even a new set of muscle fibres.

Axonal Misdirection as Contributing Factor to Aberrant Reinnervation of Muscles After Facial Nerve Suture in Cats

Whereas basic features of post-axotomy muscle reinnervation have been extensively studied in rats, little is known about axonal regrowth and pathfinding in cats. To address the question, adult cats were subjected to facial-facial anastomosis (FFA). First group served to establish optimal parameters for labeling of the zygomatic and buccal facial branches with 1, 1 ' d i o c t a d e c y l - 3, 3, 3, ' 3 ' - t e t r a m e t h y l i n d o - carbocyanine perchlorate (DiI) and Fast Blue (FB) placed onto respective transected nerves. The second group of animals underwent identical bilateral labeling 3 months after transection and suture of the right facial nerve. This group served to establish the number of motoneurons, which had branched after surgery and projected into both facial branches. On control side, DiI application onto zygomatico-orbital branch labeled 3883 ± 598 (mean ± S.D.) perikarya were confined to the dorsal and intermediate facial subnuclei, meanwhile an application of FB onto the buccal branch labeled 1617 ± 552 perikarya in the lateral and ventrolateral subnuclei. There were no double-labeled cells. Three months after FFA all retrogradely labeled motoneurons were scattered throughout the entire facial nucleus. To establish the proportion of perikarya, that re-grew multiple axonal branches into both nerves, double-labeled (FB + DiI) motoneurons were counted from digital images. The zygomatico-orbital nerve contained 3311 ± 430 DiI-labeled whereas the buccal nerve 1500 ± 442 FB-labeled motoneurons. The occurrence of 311 ± 103 double-labeled perikarya (DiI+FB) suggested that approximately 6% of all retrogradely labeled motoneurons branched axons into both nerves. I conclude that malfunctioning axonal pathfinding rather than deviant reinnervation contributed to poor recovery of function after FFA in the cat.

Histological and electrophysiological assessment of the results of primary and secondary neurorrhaphy in a rabbit model

AbstractThe effect of the timing of neurorrhaphy on neuromuscular function was studied. The gastrocnemius neuromuscular units of 22 rabbits were used, with repairs performed immediately and 3 weeks after nerve transection. At the end of 3 months, electrophysiological and histological results were compared. The study found that there was a higher rate of neuromuscular function return in primarily sutured nerves (88.0%) than in nerves repaired by secondary suture (63.0%). The histological examination also confirmed a better preserved microscopic structure of the primary repair group.