Neuroprotective Effect of Near-Infrared Light in an Animal Model of CI Surgery

Abstract

<b><i>Introduction:</i></b> The preservation of residual hearing has become an important consideration in cochlear implant (CI) recipients in recent years. It was the aim of the present animal experimental study to investigate the influence of a pretreatment with near-infrared (NIR) light on preservation of sensory hair cells and residual hearing after cochlear implantation. <b><i>Methods:</i></b> NIR was applied unilaterally (15 min, 808 nm, 120 mW) to 8 guinea pigs, immediately before a bilateral scala tympani CI electrode insertion was performed. The nonirradiated (contralateral) side served as control. Twenty-eight days postoperatively, auditory brainstem responses (ABRs) were registered from both ears to screen for hearing loss. Thereafter, the animals were sacrificed and inner hair cells (IHCs) and outer hair cells (OHCs) were counted and compared between NIR-pretreated and control (contralateral) cochleae. <b><i>Results:</i></b> There was no IHC loss upon cochlear implantation. OHC loss was most prominent on both sides at the apical part of the cochlea. NIR pretreatment led to a statistically significant reduction in OHC loss (by 39.8%). ABR recordings (across the frequencies 4–32 kHz) showed a statistically significant difference between the 2 groups and corresponds well with the apical structural damage. Hearing loss was reduced by about 20 dB on average for the NIR-pretreated group (<i>p</i> ≤ 0.05). <b><i>Discussion/Conclusion:</i></b> A single NIR pretreatment in this animal model of CI surgery appears to be neuroprotective for residual hearing. This is in line with other studies where several NIR posttreatments have protected cochlear and other neural tissues. NIR pretreatment is an inexpensive, effective, and noninvasive approach that can complement other ways of preserving residual hearing and, hence, should deserve further clinical evaluation in CI patients.

The effect of photobiomodulation on hearing loss: A systematic review

“…Overall, there was a trend toward benefit from PBMT in animal studies, irrespective of delivery method, wavelength and power used or the animal species treated. Audiological outcomes improved in all 16 animal studies following PBMT compared to no PBMT, with statistically significant improvement stated in 11 studies 12,13,19,20,22–27,29 . In the single human study included, no statistically significant effect of PBMT on hearing was detected 7 .…”

“…Ten studies assessed ABRs and showed an improvement in hearing, and inner ear elements on histology when compared to the placebo or non‐treatment group 18,20,22–25,27,29,30,31 . Hearing was better preserved or maintained in the PBMT group versus non‐PBMT group in most studies 12,13,18,20,22,23,25,26,28–31 . The effect of PBMT in reducing inflammation was also supported through histology and immunohistochemistry findings, such as increased SGNs, hair cells, and ATP 18,23,25,28 …”

“…18 One study found that pretreatment using PBMT prior to cochlear implantation resulted in better hearing outcomes. 29 Another study found a PBMT power of 165 versus 110 mW/cm 2 resulted in a greater preservation of hearing. 30 A range of otological insults were used to induce hearing losses in each animal study: noise induced hearing loss (NIHL) (n = 9), gentamicin-induced ototoxicity (n = 4), surgical trauma (n = 1), oubain-induced auditory neuropathy (n = 1) and pre-treatment for CI surgery induced hearing loss (n = 1).…”

“…Seventeen studies met the inclusion criteria with a total of 397 subjects (30 humans in a single study, 327 animals in 11 studies, and 40 animal specimens in 5 laboratory studies). 7,12,13,[18][19][20][21][22][23][24][25][26][27][28][29][30][31] Only one study, a randomised controlled trial, assessed the effect of PBMT on humans. Subjects were selected for inclusion using an unspecified screening questionnaire and randomly allocated to a control, treatment and placebo group.…”

The Role of Low-Level Laser Therapy in the Treatment of Multiple Sclerosis: A Review Study

“…16,17 Due to the beneficial effects of LLLT, it is widely used as a treatment approach in a variety of diseases. [18][19][20][21] One of the important effects of laser radiation is the inhibition of apoptosis and regulating cell viability. 22 It was shown that low-power laser radiation caused the sharp expression of the B-cell lymphoma 2 (Bcl-2) antiapoptotic gene.…”