Chung-Ku Rhee

Audiologic evaluation of neonates with severe hyperbilirubinemia using transiently evoked otoacoustic emissions and auditory brainstem responses.

Objectives: To audiologically clarify the lesion site and to test the reliability of transiently evoked otoacoustic emissions (TEOAEs) in hearing screening of hyperbilirubinemic neonates.

Hypericin uptake in rabbits and nude mice transplanted with human squamous cell carcinomas: study of a new sensitizer for laser phototherapy.

Tissue uptake and biodistribution of hypericin was measured in rabbits and in nu/nu mice xenografted with P3 human squamous cell carcinoma to assess the value of this dye as an in vivo sensitizer for laser photoinactivation of solid tumors. Hypericin has absorption maxima at 545 and 590 nm with a fluorescence emission peak at 640 nm in ethanol. Dye uptake after intravenous injection was tested at 4 and 24 hours in rabbit tissues by ethanol extraction and quantitative fluorescence spectrophotometry. Maximum dye levels were seen at 4 hours in most vascular organs with lung having fivefold higher uptake than spleen followed by liver, blood, and kidney. Mice were examined after 2, 4, 6, 8, and 24 hours and after 3 and 7 days for dye uptake. The peak concentration of hypericin in murine organs was reached at 4 hours with uptake per gram of tissue as follows: lung>spleen>liver>blood>kidney>heart>gut>tumor>stomach>skin>muscle>brain. Elimination of hypericin was rapid in most murine organs with residual dye under 10% of maximum by 7 days compared to 25% to 30% retention for the squamous cell tumors and several normal tissues. These results suggest that hypericin may be a useful photosensitizer for KTP/532 laser interstitial therapy of human cancer.

Vestibular Diagnosis as Prognostic Indicator in Sudden Hearing Loss with Vertigo

The majority of episodes of sudden hearing loss are caused by inner ear disorders, often accompanied by vertigo. The patterns of hearing loss usually influence the prognosis. The purpose of this study was to analyze vestibular diagnoses in sudden hearing loss with vertigo, and to correlate them with the recovery of hearing loss. The clinical records of 125 patients with sudden hearing loss were reviewed. Various vestibular evaluations were performed in 36 patients with vertigo. The vertigo in these patients was classified as normal, unilateral hypofunction, directional preponderance, benign paroxysmal positional vertigo (BPPV), non-specific or irritative. The initial and final pure-tone audiograms of these patients were compared. The distribution of vestibular diagnoses was unilateral hypofunction in 30.6% of patients, BPPV in 25.7%, normal in 19.4%, non-specific in 11.1%, directional preponderance in 8.3% and irritative in 8.3%. The recovery of hearing in patients with vertigo was significantly worse than in those without vertigo. The recovery of hearing in patients with spinning vertigo did not differ from that of patients with non-spinning vertigo. The recovery of hearing was worst in the BPPV group, especially in the high frequency range, followed by the unilateral hypofunction group, who showed hearing thresholds between those in the BPPV group and those in the normal vestibular function test group. This study suggests that the diagnostic classification of vestibulopathy is a useful prognostic indicator of hearing recovery in sudden hearing loss with vertigo. We conclude that otolithic and semicircular canal involvement may cause poor hearing results, especially in the high frequency range.

Effect of low-level laser treatment on cochlea hair-cell recovery after acute acoustic trauma

We investigated the effect of low-level laser radiation on rescuing hair cells of the cochlea after acute acoustic trauma and hearing loss. Nine rats were exposed to noise. Starting the following day, the left ears (NL ears) of the rats were irradiated at an energy output of 100 to 165 mW/cm(2) for 60 min for 12 days in a row. The right ears (N ears) were considered as the control group. Frequency-specific hearing levels were measured before the noise exposure and also after the 1st, 3rd to 5th, 8th to 10th and 12th irradiations. After the 12th treatment, hair cells were observed using a scanning electron microscope. Compared to initial hearing levels at all frequencies, thresholds increased markedly after noise exposure. After the 12th irradiation, hearing threshold was significantly lower for the NL ears compared to the N ears. When observed using an electron microscope, the number of hair cells in the middle turn of the NL ears was significantly larger than that of the N ears. Our findings suggest that low-level laser irradiation promotes recovery of hearing thresholds after acute acoustic trauma.

Trans-canal laser irradiation reduces tinnitus perception of salicylate treated rat

The aim of this study was to find out the effect of low-level laser therapy (LLLT) on salicylate-induced tinnitus in the rat model. Fourteen Sprague-Dawley rats (8 weeks; 240-280 gm) were divided into 2 groups (study group, control group). Rats of both groups were treated with 400 mg/kg/day of sodium salicylate for 8 consecutive days. Tinnitus was monitored using GPIAS (Gap Prepulse Inhibition of Acoustic Startle) 2 h after first salicylate treatment, and every 24 h during 9 days of treatment. Rats in laser group were irradiated to each ear with wavelength of 830 nm diode laser (165 mW/cm(2)) for 30 min daily for 8 days. During salicylate treatment, rats of study group irradiated with low level laser showed significantly higher GPIAS values throughout the experiment. Therapeutic effect of LLLT is demonstrated in animal tinnitus model by means of GPIAS. Further experimental studies are needed to find possible mechanisms and better methods to improve LLLT efficacy.

Effect of low-level laser treatment on cochlea hair-cell recovery after ototoxic hearing loss

Abstract. The primary cause of hearing loss includes damage to cochlear hair cells. Low-level laser therapy (LLLT) has become a popular treatment for damaged nervous systems. Based on the idea that cochlea hair cells and neural cells are from same developmental origin, the effect of LLLT on hearing loss in animal models is evaluated. Hearing loss animal models were established, and the animals were irradiated by 830-nm diode laser once a day for 10 days. Power density of the laser treatment was 900  mW/cm2, and the fluence was 162 to 194 J. The tympanic membrane was evaluated after LLLT. Thresholds of auditory brainstem responses were evaluated before treatment, after gentamicin, and after 10 days of LLLT. Quantitative scanning electron microscopic (SEM) observations were done by counting remaining hair cells. Tympanic membranes were intact at the end of the experiment. No adverse tissue reaction was found. On SEM images, LLLT significantly increased the number of hair cells in middle and basal turns. Hearing was significantly improved by laser irradiation. After LLLT treatment, both the hearing threshold and hair-cell count significantly improved.

In vitro and in vivo photodynamic therapy of otitis media in gerbils

The aim of this study was to evaluate the antibacterial effects of photodynamic therapy (PDT) on common bacteria causing otitis media with effusion (OME).

Candidate's thesis: Platelet-activating factor-induced Hearing loss: Mediated by nitric oxide?

Objectives/Hypothesis Platelet‐activating factor (PAF)in middle ear effusion is thought to induce hearing loss. The purpose of this study is to investigate the role of nitric oxide (NO) in the mechanism of PAF‐induced hearing loss by studying the effects of PAF application on the round window membrane (RWM) with and without PAF‐antagonist NO‐blocker.

Simultaneous bilateral laser therapy accelerates recovery after noise-induced hearing loss in a rat model

Noise-induced hearing loss is a common type of hearing loss. The effects of laser therapy have been investigated from various perspectives, including in wound healing, inflammation reduction, and nerve regeneration, as well as in hearing research. A promising feature of the laser is its capability to penetrate soft tissue; depending on the wavelength, laser energy can penetrate into the deepest part of the body without damaging non-target soft tissues. Based on this idea, we developed bilateral transtympanic laser therapy, which uses simultaneous laser irradiation in both ears, and evaluated the effects of bilateral laser therapy on cochlear damage caused by noise overexposure. Thus, the purpose of this research was to assess the benefits of simultaneous bilateral laser therapy compared with unilateral laser therapy and a control. Eighteen Sprague-Dawley rats were exposed to narrow-band noise at 115 dB SPL for 6 h. Multiple auditory brainstem responses were measured after each laser irradiation, and cochlear hair cells were counted after the 15th such irradiation. The penetration depth of the 808 nm laser was also measured after sacrifice. Approximately 5% of the laser energy reached the contralateral cochlea. Both bilateral and unilateral laser therapy decreased the hearing threshold after noise overstimulation in the rat model. The bilateral laser therapy group showed faster functional recovery at all tested frequencies compared with the unilateral laser therapy group. However, there was no difference in the endpoint ABR results or final hair cell survival, which was analyzed histologically.

Narrow band CE-Chirp auditory steady-state response is more reliable than the conventional ASSR in predicting the behavioral hearing threshold

OBJECTIVE We evaluated conventional ASSR (Bio-logic MASTER II) and NB CE-Chirp ASSR thresholds as objective hearing measures in both normal and hearing loss subjects. METHODS Patients with sensorineural hearing loss and volunteer normal hearing subjects were enrolled. Pure tone thresholds at 0.5, 1, 2 and 4 kHz were compared with the corresponding thresholds measured using Bio-logic MASTER II and the Eclipse ASSR systems. The threshold differences and correlation with pure tone were measured and reliability was evaluated with Cronbachs α. In part I of the study, all subjects were included, in part II of the study, only mild hearing loss and normal hearing subjects were included. RESULTS In part I, NB CE-Chirp ASSR revealed a significantly smaller difference in threshold than conventional ASSR, a better correlation and better reliability. However, lower frequencies of NB CE-Chirp tended to be less reliable than higher frequencies. In part II, NB CE-Chirp revealed smaller threshold differences than conventional ASSR. Both correlation scores and reliability values were generally lower in the part II results. CONCLUSION NB CE-Chirp ASSR generally revealed more favorable outcomes. However, its reliability was reduced at lower frequencies and in patients with milder hearing loss.