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Peripheral nerve reconstruction using freeze-thawed muscle grafts: a comparison with group fascicular nerve grafts in a large animal model.

There is evidence to suggest that the 'freeze-thawed muscle graft' may function as an alternative to established methods of nerve reconstruction. Using a large animal model we compared this method with group fascicular nerve grafting in peripheral nerve reconstruction. We excised a 3 cm segment of right median nerve in 10 anaesthetized sheep. The resulting gaps were repaired with either group fascicular cable grafts (GFCGs) or freeze-thawed muscle grafts (FTMGs). After six months the right (grafted) and left (control) median nerves of each sheep were exposed and assessed for nerve blood flow, nerve conduction velocity and morphological indices of recovery. Nerve blood flow was reduced by 40% in those repaired with FTMGs. All the repaired nerves contained a population of significantly smaller nerve fibres and displayed a reduced peak nerve conduction velocity. Those repaired with FTMGs (mean velocity 30.96 m/s) had a peak velocity significantly faster than the GFCG group (mean 13.16 m/s). This study shows that peripheral nerve reconstruction with freeze-thawed muscle grafts compares well with repair using nerve grafts.

Animals↗

Degeneration and regeneration of peripheral nerve in the rat trigeminal system. II. Response to nerve lesions.

The course of vibrissa sensory receptor denervation and subsequent reinnervation was studied following transection or crush of the rat infraorbital nerve. Eighteen hours after nerve lesion, the large-diameter myelinated nerves supplying the lanceolate receptors of the intermediary zone and the Merkel cells of the stratum basale contained areas of focal axoplasmic abnormalities, and some of the nerve terminals exhibited vacuolization, mitochondrial swelling, and disruption of the neurofilament pattern. The Merkel cells and lanceolate receptors of the intermediary zone were completely deafferented by 24 hours after the nerve injuries. The Ruffini complex, free nerve endings and lanceolate receptors of the inner conical body, as well as the free nerve endings and lanceolate receptors of the connective tissue below the Ringwulst, were completely normal 24 hours after crush or transection of the nerve. These receptors underwent progressive degeneration from days 2 through 6 and the vibrissa was totally denervated by day 7. Regenerating axons were first seen entering the vibrissae 2 weeks after the crush lesion and 1 month following nerve transection. Except for a slight decrease in the percentage of Merkel cells innervated, vibrissae from post-crush animals were virtually indistinguishable from normal by 3 months. In contrast, vibrissae from rats subjected to the transection lesion exhibited evidence of misdirected axons and abnormally reinnervated receptors throughout the course of regeneration. Axons entering the hairs with the main vibrissal nerve were observed contributing to the innervation of the inner conical body, an area normally supplied exclusively by the conus nerve. Many of the lanceolate receptors contained multiple unmyelinated axons, and the usually highly ordered circular innervation of the inner conical body was markedly abnormal. It is suggested that these results may help explain the faulty sensory localization and abnormal sensations reported by patients suffering a peripheral nerve injury.

Animals↗

Immunogenicity and regenerative potential of acellular nerve allografts to repair peripheral nerve in rats and rabbits.

This study describes the ability of acellular nerve allografts (genetically different) to repair injured peripheral nerve in rats and rabbits. We recently reported the regeneration supporting potential and immunogenicity of acellular nerve allografts in rats. The present study extends our previous work and quantitates the extent of axonal regeneration through various nerve grafts in rats. In addition, the use of longer nerve grafts to repair rabbit peripheral nerve is described. Inbred strains of Fischer and Buffalo rats and New Zealand white and Dutch rabbits were used. Acellular grafts were prepared by repeated freezing and thawing of in situ degenerated nerves. Non-frozen predegenerated nerves were used as cellular grafts for comparison. Nerve isografts (genetically identical) were also performed. The graft length was 2.0 cm in rats and 4.0 cm in rabbits. In both rats and rabbits the cellular isografts showed the most rapid regeneration and target muscle innervation. The cellular allografts were invariably rejected and only showed limited regeneration. In contrast, acellular allografts, in spite of their mild immunogenicity, allowed significant regeneration through them. It is concluded that acellular nerve allografts are capable of supporting axonal regeneration because of their reduced immunogenicity, and thus can be used to bridge nerve gaps after nerve injury.

Animals↗

Sensory nerve conduction velocities of median, ulnar and radial nerves in patients with vibration syndrome.

OBJECTIVE: The present study aimed to clarify the range of involvement for hand-arm vibration syndrome (VS) in the median, ulnar and radial nerves of the hand. METHODS: Sensory nerve conduction velocities (SCVs) for 3 nerves in the hands and arms were examined for 34 patients with VS and 23 age-matched controls. Neuropathy types were classified by possible carpal tunnel syndrome (CTS), Guyon's syndrome and digital neuropathy in three nerves. RESULTS: SCV in the median nerve (middle finger, wrist-elbow) and ulnar nerve (little finger, wrist-elbow), and amplitudes of the median nerve (wrist-proximal and distal parts of the middle finger), ulnar nerve (wrist-proximal and distal parts of the little finger; forearm-proximal part of the little finger; upper arm-proximal part of the little finger) and radial nerve (dorsal side of the hand-thumb) were significantly reduced in VS patients compared with controls. According to subject classifications based on the results of SCV and amplitude of nerve action potential, 52.9% of VS patients displayed multi-focal neuropathy including digital neuropathy, possible CTS and/or Guyon's syndrome. CONCLUSION: These findings suggest that VS affects all three nerves in the hand. According to classification results, the main disorders of peripheral nerves comprise digital neuropathy.

Aged↗

Structural parameters of collagen nerve grafts influence peripheral nerve regeneration.

Large nerve defects require nerve grafts to allow regeneration. To avoid donor nerve problems the concept of tissue engineering was introduced into nerve surgery. However, non-neuronal grafts support axonal regeneration only to a certain extent. They lack viable Schwann cells which provide neurotrophic and neurotopic factors and guide the sprouting nerve. This experimental study used the rat sciatic nerve to bridge 2 cm nerve gaps with collagen (type I/III) tubes. The tubes were different in their physical structure (hollow versus inner collagen skeleton, different inner diameters). To improve regeneration Schwann cells were implanted. After 8 weeks the regeneration process was monitored clinically, histologically and morphometrically. Autologous nerve grafts and collagen tubes without Schwann cells served as control. In all parameters autologous nerve grafts showed best regeneration. Nerve regeneration in a noteworthy quality was also seen with hollow collagen tubes and tubes with reduced lumen, both filled with Schwann cells. The inner skeleton, however, impaired nerve regeneration independent of whether Schwann cells were added or not. This indicates that not only viable Schwann cells are an imperative prerequisite but also structural parameters determine peripheral nerve regeneration.

Animals↗

Axonal regeneration of sensory nerves is delayed by continuous intrathecal infusion of nerve growth factor.

While it is well established that nerve growth factor is growth promoting for sensory neurons in culture, it is unclear whether it serves such a function in vivo. In fact, our previous studies led to the hypothesis that nerve growth factor could actually impair axonal regeneration by reducing the neuronal cell body response to injury. In the present study, the consequence of continuous intrathecal infusion of nerve growth factor on regeneration of sensory neurons was examined in rats given a bilateral sciatic nerve crush. Rats received nerve growth factor (125 ng/h) as a continuous infusion into the subarachnoid space of the lumbar spinal cord via an osmotic minipump (Alzet); controls received cytochrome C. At seven or 10 days, the pump was removed and L4 or L5 dorsal root ganglion exposed and injected with 50 microCi of (3H)leucine. Animals were killed 24 h later, the sciatic nerves removed, cut into 3 mm segments and the radioactivity in each segment determined by liquid scintillation spectrophotometry. Maximal regeneration distances (determined from the front of the resultant transport curves) were similarly reduced (by approximately 6 mm) in nerve growth factor-infused compared to cytochrome C-infused rats. Thus, regeneration rates (determined between eight and 11 days) were unaltered by nerve growth factor infusion; regeneration rates from cytochrome C-infused and nerve growth factor-infused animals were 2.8 mm/day and 3.1 mm/day, respectively. However, nerve growth factor significantly (P < 0.005) increased the delay to onset for regeneration by two days. Taken together, the present study demonstrates that nerve growth factor delays the onset of regeneration without affecting the rate of regeneration. The results implicate the involvement of at least two signals in the regulation of axonal regeneration in dorsal root ganglion neurons. It is suggested that the loss of nerve growth factor serves as an early, induction signal regulating the onset of regeneration and that a second, unidentified signal independently serves to maintain regeneration.

Animals↗

Nerve growth factor enhances peripheral nerve regeneration in non-human primates.

Fibronectin mat implants impregnated with NGF have been successfully used in rat nerve regeneration model. The aim of this study was to assess their action in a primate model. Mats were implanted into a 5 mm gap in a peripheral nerve in Macaca fascicularis monkeys, either alone (Fn) or in the presence of nerve growth factor (Fn + NGF). Four months postoperatively, the regenerated nerve was analysed by light microscopy, and target skin reinnervation was assessed by quantification of cutaneous nerve terminals immunostained with protein gene product (PGP) antibodies. The diameter of the regenerated nerve was similar in Fn + NGF grafts and nerve autografts, but significantly larger for plain Fn grafts with evidence of more connective tissue surrounding the axons. Myelinated fibres counts showed similarities in normal control nerve, nerve autograft and Fn + NGF graft groups. However, in nerve grafted with plain Fn mats the regenerating fibres were lower in number and showed a wider variability in diameter and myelination, resulting in a significantly smaller G-ratio (axonal diameter/myelinated fibre diameter). The amount of cutaneous reinnervation was lowest in Fn graft group, while comparable amounts of skin reinnervation were observed in the Fn + NGF and autograft groups. These results suggest that Fn-mats are a suitable conduit to promote peripheral nerve regeneration also in primate, and supplying NGF locally at the lesion site can further enhance nerve regrowth.

Animals↗

Rabbit facial nerve regeneration in autologous nerve grafts after antecedent injury.

OBJECTIVE: The effect of incomplete antecedent injuries on subsequent facial nerve regeneration within cable graft repairs is not known. The purpose of this study is to compare facial nerve regeneration after an immediate and delayed neural cable graft repair. METHOD: Rabbit facial nerve regeneration after complete transectional injuries of the buccal division was compared in two experimental models. In one, a 10-mm segment of the nerve was transected, rotated 180 degrees, and immediately repaired as a cable graft (N=8). In the second, a preliminary nerve crush was allowed to recover over a 4-week period and a 10-mm segment of nerve centered on the crush site was then transected, rotated 180 degrees, and delay repaired as a cable graft (N = 7). Data are presented as total numbers of regenerating myelinated axons that traverse the surgical repair to innervate the cable graft and distal nerve stumps, as well as the percentage of regenerating neurites compared with preoperative pooled and individual controls. Subpopulations of regenerating neurons are delineated to quantify the pattern of neural innervation. RESULTS: Five weeks after cable graft repair both groups had similar myelinated outgrowth from the proximal nerve stump across the proximal anastomosis to innervate the cable graft (3995 +/- 1209 vs. 3284 +/- 651; P = .89). However, the delayed repair group had more intrafascicular regeneration within cable grafts (2261 +/- 931 vs. 1660 +/- 1169; P = .02) and distal nerve stump (1532 +/- 281 vs. 445 +/- 120; P = .004) than the immediate repair group. The immediate repair group had greater extrafascicular nerve regeneration in the cable graft (2335 +/- 1954 vs. 437 +/- 236; P = .001) and more myelin and axonal debris in pre-existing neural fascicles of the cable graft (P = .02) and distal nerve stump (463 +/- 187 vs. 103 +/- 87; P = .02). CONCLUSIONS: Antecedent priming lesions do not enhance axonal survival as determined by regenerating myelinated axonal counts. However, antecedent injuries enhance the efficiency of neural innervation of the affected mimetic musculature by increasing the number of myelinated intrafascicular neural regenerants in the cable graft and distal nerve stump. This is accomplished by two factors: increased perineural fibrosis and decreased intrafascicular myelin and axonal debris.

Animals↗

[The influence of nerve growth factor on inferior alveolar nerves regeneration in the silicone tubes].

OBJECTIVE: To explore the effect of exogenous nerve growth factor(NGF) in the regeneration of adult white rabbits inferior alveolar nerve within the silicone tubes. METHODS: In 24 adults white rabbits. A bilateral 8 mm inferior alveolar nerve gaps were created, and the proximal and distal stumps were inserted into a 12 mm silicone tube. The silicone tube of the right side was filled with exogenous NGF(experimental group) and the contralateral side was filled with saline (control group). Regeneration of the nerves was assessed by histological exam and nerve electrophysiological appreciation. Total number of the regenerating myelinated nerve fibers, the conduction velocities of nerves the thickness of myelin sheaths and the cross section area of myelinated nerve fibers between the experimental and the control groups were compared. RESULTS: The results showed that: 1. The experimental groups demonstrated more myelinated nerve fibers than that of the controls in 12 and 18 weeks. 2. At the same time following surgery, the myelin sheath thickness and the cross section area of myelinated nerves in the experimental groups were significantly greater than that in the controls. 3. In 12 and 18 weeks, the conduction velocities of regenerating nerves in the experimental groups were faster than that of the controls. CONCLUSION: This study suggested that exogenous NGF can enhance regeneration of inferior alveolar nerve with necovery of its sensory function.

Animals↗

[Effect of subcutaneous implant of peripheral nerve allograft on sciatic nerve regeneration in rats].

OBJECTIVE: To study the effect of subcutaneous implant of peripheral nerve allograft on sciatic nerve regeneration in rats. METHODS: Out of 30 male Wistar rats, 6 were donors and 24 were divided randomly into 2 groups. In experimental group (group A, n = 12), a 15 mm segment of sciatic nerve harvested from donors was separately inserted into subcutaneous compartment on the right thigh; two weeks later, the segment of sciatic nerve in subcutaneous compartment was removed and transplanted into a 10 mm sciatic nerve defect of left, which was made immediately. In the control group (group B, n = 12), a 10 mm sciatic nerve defect was made and immediately repaired in situ on the left thigh. The regeneration of sciatic nerve was examined histologically (after 2, 4, 8, and 14 weeks) and electrophysiologically (after 14 weeks of operation). RESULTS: After 2 weeks of operation, the inflammatory reaction was a little stronger in group A than in group B. After 4 weeks, the intensity of the inflammatory reaction was similar between two groups; some collagen fibers proliferated. After 8 weeks, the inflammatory reaction ended and the collagen fibers proliferated obviously. After 14 weeks of operation, the structure of epineurium was in integrity and there was no obvious difference in perineurium and endonurium between two groups. A large number of myelinated nerve fibers and a small number of unmyelinated nerve fibers regenerated. The structure of myelin sheath was in integrity. The number and size of regenerated axon had no significant difference between two groups(P > 0.05). The conduction velocity, the peak value and the latent period of motor nerve were no significant difference between two groups (P > 0.05). CONCLUSION: The allograft of sciatic nerve inserted into subcutaneous compartment can promote nerve regeneration.

Animals↗

Spinal nerve root origins of the cutaneous nerves arising from the canine brachial plexus.

The spinal nerve root origins of the cutaneous nerves arising from the brachial plexus were investigated in 10 babiturate-anesthetized dogs by stimulating dorsal roots C5 to T2 and recording from each cutaneous nerve. Upon completion of the experiment, the contributions of the spinal nerve ventral branches to the brachial plexus were verified by anatomic dissection. The brachial plexus was formed by the ventral branches of C6 to T2 in 8 dogs, C6 to T1 in 1 dog, and C5 to T1 in 1 dog. The cutaneous branch of brachiocephalicus nerve was formed primarily by contributions from the C6 dorsal root. The cranial lateral cutaneous brachial nerve, a branch of the axillary nerve, was formed predominantly from C6 to C7. The median nerve received contributions primarily from C7, C8, and T1, and the communicating branch from the musculocutaneous to the median nerve contained fibers primarily from C7 and C8. The medial and lateral branches of the superficial branch of the radial nerve arose from C6, C7, C8, and T1, with the medial branch generally arising 1 segment craniad to the lateral. The palmar and dorsal branches of the ulnar nerve arose predominately from C8 and T1, and the caudal cutaneous antebrachial nerve of the ulnar arose predominately from T1 and T2.

Action Potentials↗

Nerve repair by means of tubulization: literature review and personal clinical experience comparing biological and synthetic conduits for sensory nerve repair.

Nerve repair is usually accomplished by direct suture when the two stumps can be approximated without tension. In the presence of a nerve defect, the placement of an autologous nerve graft is the current gold standard for nerve restoration. However, over the last 20 years, an increasing number of research articles reported on the use of non-nervous tubes (tubulization) for repairing nerve defects. The clinical employment of tubes (both biological and synthetic) as an alternative to autogenous nerve grafts is mainly justified by the limited availability of donor tissue for nerve autografts and the related morbidity. In addition, tubulization was proposed as an alternative to direct nerve sutures in order to create optimal conditions for nerve regeneration over the short empty space intentionally left between two nerve stumps. This paper outlines recent important advances in this field. Different tubulization techniques proposed so far are described, focusing in particular on studies that reported on the employment of tubes with patients. Our personal clinical experience on tubulization repair of sensory nerve lesions (digital nerves), using both biological and synthetic tubes, is presented, and the clinical results are compared. In our case series, both types of tubes led to good clinical results. Finally, we speculate about the prospects in the clinical application of tubulization for peripheral nerve repair.

Bioprosthesis↗

An electron microscopic study on the blood-optic nerve and fluid-optic nerve barrier.

Utilizing horseradish peroxidase as a tracer, electron microscopic studies were done on the blood-optic nerve and fluid-optic nerve barrier to the peroxidase diffusion. Following intravenous injection the peroxidase was observed to fill the lumen of the capillaries of the laminar, prelaminar and orbital portions of the optic nerve but there was no penetratation of the capillary walls. The obstruction of the tracer diffusion out of capillary walls was attributed to the tight junctions between the endothelial cells. Peroxidase penetration was also absent in the capillaries of the pia and dura mater, however, was observed in pinocytotic vesicles of the endothelial cells. Lateral diffusion from the surrounding choroid into the optic nerve was detected but diffusion from the prelaminar optic nerve into the juxta-optic nerve retina was prevented by the Kuhnt intermediary tissue. Tight junctions which prevented peroxidase diffusion were found between the glial cells of the Kuhnt tissue, and this tissue was the barrier between the prelaminar optic nerve and the juxta-optic nerve retina. Peroxidase which was given into the lateral ventricle of the brain appeared in the subarachnoidal space around the optic nerve and penetrated freely into the optic nerve. The pial surface of the optic nerve possess no barrier activity. Peroxidase could be traced along the intercellular space between glial cells and optic nerve fibers. The basal lamina of the optic nerve capillaries was filled with peroxidase but diffusion into the capillary lumen was obstructured by the tight junctions between the endothelial cells.

Animals↗

Saphenous nerve anaesthesia--a nerve stimulator technique.

PURPOSE: This two part study was undertaken to assess both the feasibility of identifying the saphenous nerve with a nerve stimulator and to assess the efficacy of saphenous nerve anaesthesia with electrical isolation of the nerve. METHODS: (Part I): In Part I we studied 25 volunteers. Each had saphenous nerve blocks performed using a nerve stimulator (NS) and loss of resistance (LOR) technique. We recorded 10 cm linear visual analogue pain scores on completion of the blocks, time to completion of the blocks, onset time, and success of the blocks. (Part II): Clinical utility of the NS technique of saphenous nerve block was investigated. We evaluated the NS technique in 21 consecutive patients having surgery below the knee. RESULTS: (Part I): The LOR technique successfully produced saphenous nerve anaesthesia in 18/25 (72%) volunteers and the NS technique was successful in all volunteers (25/25-P < 0.05). The nerve stimulator approach required more time to complete (NS 13 +/- 7 min vs LOR 8 +/- 2 min; P < 0.05). Visual analogue pain scores differed (P < 0.05) with a median of 1.0 cm for the LOR technique and a median of 2 cm for the NS technique. (Part II): The saphenous nerve block was successful in 20/21 (95%) of the patients. CONCLUSIONS: (Part I): The first part of the study established the feasibility of electrical identification of the saphenous nerve and demonstrated that the NS technique could be utilized to provide superior anaesthesia of the saphenous nerve when compared with a previously validated LOR technique. (Part II): The clinical utility of the NS technique of saphenous nerve block was successfully demonstrated.

Adolescent↗

Distribution of sodium channels during nerve elongation in rat peripheral nerve.

A number of studies have investigated electrophysiological and morphological changes of peripheral nerves during gradual elongation. There has been, however, no report on the distribution of sodium channels at Ranvier's nodes during peripheral nerve elongation. We investigated peripheral nerve injury after the gradual elongation of rat sciatic nerves. Indirect nerve elongation was induced by leg lengthening at a rate of 3 mm/day by 15 or 30 mm. At 7 days after the leg lengthening, the electrophysiological properties of sciatic nerves, the ultrastructures of the Ranvier's nodes and axons, and the distribution of voltage-dependent sodium channels were examined. In the control nerves, most sodium channels were localized at Ranvier's nodes in myelinated axons, providing the physiological basis of saltatory conduction. In the elongated nerves, both the amplitude and conduction velocity of compound nerve action potential decreased following leg lengthening. The elongated nerves also showed paranodal demyelination in Ranvier's nodes longer than those in the control group. In addition, the distribution of sodium channels became diffuse or disappeared at Ranvier's nodes of elongated nerves. The diffuse distribution and/or disappearance of sodium channels may underlie the electrophysiological changes in compound nerve action potential induced by nerve elongation.

Animals↗

Free vascularized nerve grafting for immediate facial nerve reconstruction.

OBJECTIVES/HYPOTHESIS: To obtain better functional results after reconstruction to treat facial palsy in the patients with preoperative and intraoperative factors that might inhibit functional recovery, the authors have used free vascularized nerve grafts to immediately reconstruct severed facial nerves. STUDY DESIGN: The indications for vascularized nerve grafts were 1) scarred recipient bed attributable to previous operations, 2) a history of previous irradiation at the wound, 3) facial skin defects over the nerve graft after tumor ablation, 4) patient age greater than 60 years, and 5) preoperative facial palsy. METHODS: Four types of free vascularized nerves were used. Functional recovery after reconstruction could be assessed with two facial nerve grading systems.Ten patients who underwent immediate reconstruction of severed facial nerve after ablative surgery of malignant tumors of the parotid gland were reviewed. RESULTS: Functional recovery after reconstruction could be assessed with the House-Brackmann grading system and a 40-point grading system in 6 of the 10 patients after a mean follow-up period of 29.8 months (range, 10-60 mo). Results with the House-Brackmann system were grade II in 1 patient, grade III in 4 patients, and grade IV in 1 patient; scores on the 40-point grading system were 20 in 1 patient, 22 in 3 patients, 24 in 1 patient, and 28 in 1 patient. CONCLUSION: The study results indicated that muscle movement recovers satisfactorily after free vascularized nerve grafting. Although a study comparing vascularized nerve grafts and conventional nerve grafts would be necessary to confirm the superiority of vascularized nerve grafts, free vascularized nerve grafts are effective for immediate reconstruction of the severed facial nerve in patients with preoperative and intraoperative factors that might inhibit functional recovery.

Aged↗

[Treatment of recurrent laryngeal nerve paralysis by several types of nerve suture].

Although simple neurorrhaphy of the injured recurrent laryngeal nerve usually results in impaired movements of the vocal cord because of misdirected regeneration, phonation recovers because the vocal cord maintains tension during phonation. Simple neurorrhaphy is possible in only a few of patients who have had their nerve severed because of thyroid surgery for thyroid cancer. We tried free nerve grafting, vagus nerve-recurrent nerve suture and ansa cervicalis-recurrent nerve suture as well as the simple neurorrhaphy in 3, 1, 1 and 3 patients, respectively. All of the 8 patients who had repair of the recurrent nerve recovered from hoarseness. Maximum phonation times of these patients ranged from 17 to 41 sec with a mean of 26.5 +/- 9.6 sec, which were significantly longer than those of 23 patients without nerve repair. Each modality of the repair obtained similar good results, although the patient who underwent vagus-recurrent suture required a longer period for recovery. These results indicate that not only simple neurorrhaphy of the recurrent nerve but also free nerve grafting, vagus nerve-recurrent nerve suture, or ansa cervicalis-recurrent suture are effective in recovery of the phonation in patients with peripheral and unilateral recurrent nerve paralysis.

Adolescent↗

The re-innervation of the tongue and salivary glands after lingual nerve repair by stretch, sural nerve graft or frozen muscle graft.

The lingual nerve is sometimes injured during the surgical removal of impacted third molar teeth and may require repair. Removal of the damaged section of nerve prior to repair leaves a gap between the nerve ends, and we have investigated methods of closing the gap. THe characteristics of regenerated fibers in the chorda tympani have been recorded in cats 24 weeks after the removal of a segment of lingual nerve and repair of the defect by three methods. The nerve gap was closed either by stretching the nerve ends together and repairing under tension, or by the insertion of a sural nerve graft or freeze-thawed muscle graft. The properties of gustatory, thermosensitive, and mechanosensitive units and the return of the vasomotor and secretomotor responses were investigated by electrophysiological techniques and the data from each of the repair groups compared with those obtained from a series of normal control animals. After each method of repair, the integrated whole-nerve activity recorded from the chorda tympani during gustatory or thermal stimulation of the tongue was reduced when compared with controls, but there was little significant difference between the repair groups. Recordings made from single units in the chorda tympani revealed that conduction velocities were faster after stretch repair than after sural nerve graft or frozen muscle graft. In addition, 48% of the units had developed into principally gustatory units after stretch repair, indicating a better level of recovery than in the graft groups, which contained 33% and 32%, respectively. The secretomotor responses were also significantly greater after stretch repair than in either of the graft groups or the controls, but there was no difference in the vasomotor responses. These results reveal that repair of a short gap in the lingual nerve by stretching the ends together is followed by better overall recovery than after grafting, but where a graft is used, a similar level of recovery results from use of a frozen muscle graft or a sural nerve graft.

Anastomosis, Surgical↗