CO2 laser repair of the facial nerve: an experimental study in the rat

Light-Activated Sealing of Nerve Graft Coaptation Sites Improves Outcome following Large Gap Peripheral Nerve Injury

BACKGROUND

Nerve repair using photochemically bonded human amnion nerve wraps can result in superior outcomes in comparison with standard suture. When applied to nerve grafts, efficacy has been limited by proteolytic degradation of bonded amnion during extended periods of recovery. Chemical cross-linking of amnion before bonding may improve wrap durability and efficacy.

METHODS

Three nerve wraps (amnion, cross-linked amnion, and cross-linked swine intestinal submucosa) and three fixation methods (suture, fibrin glue, and photochemical bonding) were investigated. One hundred ten Lewis rats had 15-mm left sciatic nerve gaps repaired with isografts. Nine groups (n = 10) had isografts secured by one of the aforementioned wrap/fixation combinations. Positive and negative control groups (n = 10) were repaired with graft and suture and no repair, respectively. Outcomes were assessed using sciatic function index, muscle mass retention, and histomorphometry. Statistical analysis was performed using analysis of variance and the post hoc Bonferroni test (p < 0.05).

RESULTS

Cross-linking improved amnion durability. Photochemically bonded cross-linked amnion recovered the greatest sciatic function index, although this was not significant in comparison with graft and suture. Photochemically bonded cross-linked amnion recovered significantly greater muscle mass (67.3 ± 4.4 percent versus 60.0 ± 5.2 percent; p = 0.02), fiber diameter, axon diameter, and myelin thickness (6.87 ± 2.23 μm versus 5.47 ± 1.70 μm; 4.51 ± 1.83 μm versus 3.50 ± 1.44 μm; and 2.35 ± 0.64 μm versus 1.96 ± 0.47 μm, respectively) in comparison with graft and suture.

CONCLUSION

Light-activated sealing of cross-linked human amnion results in superior outcomes when compared with conventional suture.

Histopathological and electrophysiological study of CO(2), Er:YAG, and CO (2) + Er:YAG laser effect on peripheral nerve

BACKGROUND

The purpose of this study was to investigate the morphological, histopathological, and electrophysiological changes of peripheral nerve after CO(2) (carbon dioxide), Er:YAG (erbium:yttrium aluminum garnet), and CO(2) + Er:YAG laser irradiation. There have been no comparative reports on CO(2), Er:YAG, and CO(2) + Er:YAG laser effects on peripheral nerve.

METHODS

Thirty Wistar albino rats were randomly assigned to three groups. Group I received CO(2), group II Er:YAG, and group III CO(2) + Er:YAG laser irradiation. Contralateral untreated sciatic nerves from the same animals were used as controls. The effect of laser on the peripheral nerve was assessed morphologically, histopathologically, and electrophysiologically after 6 weeks of laser irradiation.

RESULTS

No significant difference was observed between the treated and the untreated nerves.

CONCLUSION

The overall findings indicated that CO(2), Er:YAG, and CO(2) + Er:YAG lasers may be used safely in nerve tissue surgery.

Photochemical Tissue Bonding: A Promising Technique for Peripheral Nerve Repair

BACKGROUND

Photochemical tissue bonding (PTB) is a novel tissue repair technique that uses visible light and a photosensitizing dye to crosslink proteins on tissue surfaces. This technique has been successfully demonstrated in a number of tissue repair models. An ideal nerve repair technique would be atraumatic and avoid placement of foreign bodies at the repair site. The epineurium is suited to photochemical repair as it is thin, translucent and has a relatively high collagen content. This study was designed to determine if PTB could be successfully applied in a peripheral nerve repair model.

MATERIAL AND METHODS

Forty Sprague Dawley rats underwent transection of the sciatic nerve. Animals were then randomized to four treatment groups; epineurial suture repair, epineurial cuff with PTB, epineurial cuff alone, and no repair. Functional recovery was assessed at 10 day intervals using walking track analysis and sciatic function index calculations. At 90 days postoperatively animals were sacrificed and sciatic nerves harvested for histology and histomorphometry.

RESULTS

Functional recovery in the suture repair and epineural cuff with PTB groups were not significantly different (-70.6 +/- 17.8 versus -76.9 +/- 10.3, P = 0.64) at 90 days postrepair. Histology showed good axonal regeneration with all repair techniques. Histomorphometric analysis found no significant difference between the repair groups.

CONCLUSIONS

This study illustrates that peripheral nerves can be successfully repaired using a photochemical tissue bonding technique with results similar to those achieved with the current gold standard. With further development and refinement PTB may prove a useful tool in peripheral nerve repair.

A novel method of head fixation for the study of rodent facial function

The rodent vibrissial system offers an excellent model for the study of both sensory and motor function. It has been widely employed to gather data pertaining to sensory and motor function involving the 5th and 7th cranial nerves and the central nervous system. Existing methods of head fixation for precise measurements of ocular and vibrissial function involve exposing the cranium and applying dental cement from which two or more threaded rods emerge. This common approach is suboptimal, requiring a relatively complicated implantation procedure, and results in a large, chronic interface between the scalp and environmentally exposed implant material attached to the skull. Here we describe a head fixation device that is inexpensive, easy to build, less prone to infection, preserves access to the cranial midline, and permits repeated measurements over many months.

Somatotopic organization of the facial nucleus is disrupted after lesioning and regeneration of the facial nerve: the histological representation of synkinesis

OBJECTIVE

After facial nerve repair, involuntary movement of part of the face during voluntary movement of another part of the face is common. We describe an animal model of facial nerve lesion, repair, and regeneration that demonstrates abnormal organization of the facial nucleus; this model may be used to study synkinesis.

METHODS

In 18 rats, the facial nerve was cut completely, proximal to the parotid gland, and immediately sutured end-to-end. After a period of regeneration of 1 to 10 months, retrograde fluorescence labeling of the distal branches of the facial nerve was performed. The distribution of the tracers in the facial nucleus was assessed in both the lesioned animals and in a nonlesioned group (n = 20).

RESULTS

In the control animals, muscle groups were somatotopically represented in the facial nucleus. After lesioning, repair, and regeneration, the somatotopy of the facial nucleus was disrupted. Axons projected from the facial nucleus to incorrect peripheral muscle groups, and aberrant branches were observed to simultaneously innervate different subdivisions of the facial nerve. The numbers of aberrant axons and branches did not change significantly during periods of regeneration ranging from 1 to 10 months.

CONCLUSION

Our model provides a clear demonstration of the failure of adult facial nerve axons to make correct connections with their distal targets during regeneration. This model may be used to assess strategies aimed at minimizing synkinesis and, by assessing histology together with behavior, provides a more robust model than those previously described.

Laser, fibrin glue, or suture repair of peripheral nerves: a comparative functional, histological, and morphometric study in the rat sciatic nerve

OBJECT

This study was undertaken to evaluate CO2 laser-assisted nerve repair and compare it with nerve repair performed with fibrin glue or absorbable sutures.

METHODS

In eight rats, the sciatic nerve was sharply transected and approximated using two 10-0 absorbable sutures and then fused by means of CO2 milliwatt laser welding (power 100 mW, exposure time 1 second per pulse, spot size 320 microm), with the addition of a protein solder (bovine albumin) to reinforce the repair site. The control groups consisted of eight rats in which the nerves were approximated with two 10-0 absorbable sutures and subsequently glued using a fibrin sealant (Tissucol), and eight rats in which the nerves were repaired using conventional microsurgical sutures (four to six 10-0 sutures in the perineurium or epineurium). Evaluation was performed 16 weeks postsurgery and included the toe-spreading test and light microscopy and morphometric assessment. The motor function of the nerves in all groups showed gradual improvement with time. At 16 weeks, the motor function was approximately 60% of the normal function, and there were no significant differences among the groups. On histological studies, all nerves revealed various degrees of axonal regeneration, with myelinated fibers in the distal nerve segments. There were slight differences in favor of the group treated with laser repair, in terms of wound healing at the repair site. In all groups, the number of axons distal to the repair site was higher compared with those proximal, but the axon diameter was significantly less than that in control nerves (p < 0.05). There were no significant differences in the number, density, or diameter of the axons in the proximal or distal nerve segments among the three nerve repair groups (p < 0.05), although there was a trend toward more and thicker myelinated axons in the distal segments of the laser-repaired nerves.

CONCLUSIONS

It was found that CO2 laser-assisted nerve repair with soldering is at least equal to fibrin glue and suture repair in effectiveness in a rodent model of sciatic nerve repair.