Effect of CO2-milliwatt laser on peripheral nerves: Part II. A histological and functional study

Abstract

In order to further explore the role of laser for microneural repair, the early and late effects of CO(2) laser irradiation on intact rat sciatic nerves were investigated. A total of 48 rat sciatic nerves were exposed to 100-mW laser power with a pulse duration of 1.0 s and a spot size of 320 microm. In one-half of the nerves, albumin solder was applied to the nerve followed by laser irradiation. The results were evaluated up to 94 days after surgery with functional toe-spreading test, and light and transmission electron microscopy. Irradiation of the nerve resulted in almost no deficit in the motor function. A subperineurial degeneration of myelinated and unmyelinated axons is observed in the first 2 weeks after laser irradiation, while the central part of the nerve remains undamaged. The degeneration is followed by axonal regeneration with subsequent maturation of nerve fibres in time. No excessive intraneural or extraneural scarring was seen. In the soldered nerves, the solder elicits an inflammatory reaction upon the epineurium in the first week after irradiation. By week 1, the solder is completely absorbed. After 2 weeks, the inflammatory reaction ceases and by week 4, no residual reaction is seen. At 12 weeks, only minimally disarranged epineurium is seen with otherwise normal neural architecture. In conclusion, CO(2) laser irradiation at 100 mW with pulses of 1.0 s has no long term negative effects on nerve function and morphology. Therefore, these laser settings can be safely applied for laser-assisted nerve repair.

Skin denervation, neuropathology, and neuropathic pain in a laser-induced focal neuropathy

“…The immediate thermal effect of laser irradiation in the current report was limited to the subepineurial region and depended on the nature and dose of the laser. This is in contrast to the CO 2 laser, which causes much more extensive thermal injury than the diode laser of 532 nm used in the current system (Menovsky et al, 1996(Menovsky et al, , 2000; after CO 2 laser irradiation on sciatic nerves, both the epineurium and endoneurium are severely damaged by the thermal effect. The entire nerve becomes edematous, and pyknotic nuclei appear in fibroblasts.…”

Skin denervation, neuropathology, and neuropathic pain in a laser-induced focal neuropathy

“…The immediate thermal effect of laser irradiation in the current report was limited to the subepineurial region and depended on the nature and dose of the laser. This is in contrast to the CO 2 laser, which causes much more extensive thermal injury than the diode laser of 532 nm used in the current system (Menovsky et al, 1996(Menovsky et al, , 2000; after CO 2 laser irradiation on sciatic nerves, both the epineurium and endoneurium are severely damaged by the thermal effect. The entire nerve becomes edematous, and pyknotic nuclei appear in fibroblasts.…”

The differentiation of oral soft‐ and hard tissues using laser induced breakdown spectroscopy – a prospect for tissue specific laser surgery

“…Here, by recording and analyzing the resulting process emissions, the laser may be shut down upon reaching the cortical layer, before even reaching the nerve tissue . Although the low number of LIBS shots (one or two) that are necessary to identify the nerve tissue are not expected to cause significant damage, it is certainly more favorable to stop the ablation process at the final cortical layer and to avoid any risk that might arise from the ablation of the nerve . The differentiation performance of the cortical/cancellous‐bone:nerve pairs is equivalent to the performance of the Ca:C ratio‐based hard‐soft tissue differentiator (Sens./Spec.…”

In vitro and in vivo tissue repair with laser‐activated chitosan adhesive

“…During the procedure, the surgeon irradiated the chitosan strips for longer than necessary because the adhesive activation lacked a visual end point. A reduction in fluence and temperatures are therefore needed to avoid or diminish nerve thermal damage; it also may prove beneficial to irradiate the adhesive with pulses rather than in continuous wave, as previously reported [20].…”

Skin denervation, neuropathology, and neuropathic pain in a laser-induced focal neuropathy

“…The immediate thermal effect of laser irradiation in the current report was limited to the subepineurial region and depended on the nature and dose of the laser. This is in contrast to the CO 2 laser, which causes much more extensive thermal injury than the diode laser of 532 nm used in the current system (Menovsky et al, 1996(Menovsky et al, , 2000; after CO 2 laser irradiation on sciatic nerves, both the epineurium and endoneurium are severely damaged by the thermal effect. The entire nerve becomes edematous, and pyknotic nuclei appear in fibroblasts.…”

The differentiation of oral soft‐ and hard tissues using laser induced breakdown spectroscopy – a prospect for tissue specific laser surgery

“…Here, by recording and analyzing the resulting process emissions, the laser may be shut down upon reaching the cortical layer, before even reaching the nerve tissue . Although the low number of LIBS shots (one or two) that are necessary to identify the nerve tissue are not expected to cause significant damage, it is certainly more favorable to stop the ablation process at the final cortical layer and to avoid any risk that might arise from the ablation of the nerve . The differentiation performance of the cortical/cancellous‐bone:nerve pairs is equivalent to the performance of the Ca:C ratio‐based hard‐soft tissue differentiator (Sens./Spec.…”

In vitro and in vivo tissue repair with laser‐activated chitosan adhesive

“…During the procedure, the surgeon irradiated the chitosan strips for longer than necessary because the adhesive activation lacked a visual end point. A reduction in fluence and temperatures are therefore needed to avoid or diminish nerve thermal damage; it also may prove beneficial to irradiate the adhesive with pulses rather than in continuous wave, as previously reported [20].…”

Skin denervation, neuropathology, and neuropathic pain in a laser-induced focal neuropathy

“…The immediate thermal effect of laser irradiation in the current report was limited to the subepineurial region and depended on the nature and dose of the laser. This is in contrast to the CO 2 laser, which causes much more extensive thermal injury than the diode laser of 532 nm used in the current system (Menovsky et al, 1996(Menovsky et al, , 2000; after CO 2 laser irradiation on sciatic nerves, both the epineurium and endoneurium are severely damaged by the thermal effect. The entire nerve becomes edematous, and pyknotic nuclei appear in fibroblasts.…”

The differentiation of oral soft‐ and hard tissues using laser induced breakdown spectroscopy – a prospect for tissue specific laser surgery

“…Here, by recording and analyzing the resulting process emissions, the laser may be shut down upon reaching the cortical layer, before even reaching the nerve tissue . Although the low number of LIBS shots (one or two) that are necessary to identify the nerve tissue are not expected to cause significant damage, it is certainly more favorable to stop the ablation process at the final cortical layer and to avoid any risk that might arise from the ablation of the nerve . The differentiation performance of the cortical/cancellous‐bone:nerve pairs is equivalent to the performance of the Ca:C ratio‐based hard‐soft tissue differentiator (Sens./Spec.…”

In vitro and in vivo tissue repair with laser‐activated chitosan adhesive

“…During the procedure, the surgeon irradiated the chitosan strips for longer than necessary because the adhesive activation lacked a visual end point. A reduction in fluence and temperatures are therefore needed to avoid or diminish nerve thermal damage; it also may prove beneficial to irradiate the adhesive with pulses rather than in continuous wave, as previously reported [20].…”