Photobiomodulation at a wavelength of 633 nm leads to faster functional recovery than 804 nm after facial nerve injury

Abstract

We analyzed the effects of photobiomodulation (PBM) of various wavelengths on regeneration of the facial nerve using in vitro and in vivo experimental models. We assessed the antioxidative effect of PBM in geniculate ganglion neurons irradiated with a diode laser at 633 nm, 780 nm and 804 nm. Wavelengths of 633 and 780 nm but not 804 nm inhibited cell death by oxidative stress. We assessed the effects of PBM on functional and morphologic recovery in rats divided into control, facial nerve damage (FND) and FND irradiated with a 633 nm or 804 nm lasers. Injured rats treated with 633-nm light had better facial palsy scores, larger axon diameter and higher expression of Schwann cells compared with the FND group. No positive results were observed in rats irradiated at 804-nm light. These findings indicate that 633-nm PBM promotes accelerated nerve regeneration and improved functional recovery in an injured facial nerve.

Management of Bell’s Palsy with Phototherapy

“…They found that laser at 660 nm provided early functional nerve recovery compared to other groups. Another animal study by Lee et al [53] also showed that rats with facial nerve injuries responded positively to 633 nm light, with better facial palsy scores, larger axon diameter, and higher expression of Schwann cells, but not to 804 nm light. One of our included studies used a laser at 780 nm during the early stage of treatment, aiming for a deeper penetration [37].…”

“…Existing evidence suggests that LLLT acts on the mitochondria and cell membrane chromophores to initiate the biological response [51]. Studies have suggested the possibility of using defined wavelengths for particular biological responses, hence achieving specific therapeutic effects [52,53]. Barbosa et al [52] compared the effects of LLLT at 660 nm and 830 nm on sciatic nerve regeneration following crushing injuries in rat models.…”

Effects of low-level laser therapy on utricular hair cell regeneration: a review of the efficacy of available treatment parameters

“…Corresponding results showed that 633 nm provided better facial nerve recovery by reducing reactive oxygen species in vitro and axonal regeneration as well as Schwann cell recruitment in vivo. 36 However, significant studies showed that the use of 808 provided promising results with auditory nerve stimulation as well as functional recovery after hearing loss. 37 A relevant study performed by Tamura et al 38 using 808 nm at either 110 or 165 mW/cm 2 resulted in a protective mechanism against noise-induced hearing loss via inducible nitric oxide synthase (iNOS) inhibition.…”