The Experimental And Clinical Study On Intratympanic Dexamethasone Injections For Refractory Sudden Sensorineural Hearing Loss

PART ONE: The effect of hyaluronic acid with gelfoam on penetrating of dexamethasone across the round window membraneOBJECTIVE The goal of this study was to investigate the concentration of dexamethasone in the perilymph of guinea pigs, and the effect of hyaluronic acid with gelfoam on the penetrating of dexamethasone across the round window membrane.METHOD Thirty- six healthy guinea pigs with normal Preyer's reflex weighed 300 to 500g were used in this study.According to the time of injections,they were randomly divided into three groups:the one day group,the four day group and seven day group,every group had 12 guinea pigs, which were randomly separated into experimental group and control group, the right ear of each guinea pig was defined as experimental ear. Gelfoam soaked with hyaluronic acid was placed on the round window in the experimental group, and gelfoam only in the control group. Dexamethasone (0.15ml～0.20ml) was perfused transtympanically through round window catheter placement, the perfusion was taken twice a day, the perilymph of the scala tympani was sampled at 45 min after dexamethasone administrations on the 1th, 4th and 7th day separately, dexamethasone in the samples was assayed by HPLC. A separation was performed on a Diamonsil C18 column with 7.56 mmol·L^-1 ammonium sulfate-acetonitrile (70: 30) as mobile phase at the flow rate of 1.0 mL·min^-1. The temperature of column was at 35℃, the wavelength of detection was 239 nm. RESULTS The concentration of dexamethasone in the perilymph of guinea pig of experimental group was higher than that in the control group.(P＜0.01), There was not significant difference among three groups (P＞0.05)CONCLUSION This study demonstrates that hyaluronic acid with gelfoam could facilitate the penetrating of dexamethasone across the round window membrane. PART TWO: Round window catheter placement with dexamethasone perfusion for refractory sudden sensorineural hearing lossOBJECTIVE To investigate the efficacy of round window catheter placement with dexamethasone (DXM) perfusion for 23 patients with refractory sudden sensorineural hearing loss (SSNHL).METHOD For the 23 patients with refractory SSNHL as DXM perfusion group,DXM (2.5mg/0.5ml) was perfused transtympanically through round window catheter placement by Micro-infusion pump twice a day for 1 hour each time, for a total of 7 days .Audiological results were compared between the DXM perfusion group and the control group(n=18) who refused to receive the further perfusion treatment.The two groups were matched with respect to hearing loss after initial systemic treatment failture(P＞0.05).RESULT Following up for 1 month,the PTA of 23 patients who received DXM perfusion treatment demonstrated that hearing of 9 patients(39.1%) was improved about 17-54dB,14 patients(60.9%) had no change.All patients tolerated the procedure well and there were no tympanic membrane perforation or infection.CONCLUSION Our study revealed that round window catheter placement with dexamethasone perfusion is a safe and effective treatment for SSNHL patients who had no response to the conventional therapy.