Intracochlear Distribution of Intra-tympanically Injected QDDNs in Rats and Analysis of the Hearing Recovery According to the Frequency in SSNHL

Intratympanic dexamethasone (IT-DEX) injection is a useful treatment option for patients that fail systemic steroid therapy for treatment of sudden idiopathic sensorineural hearing loss (SSNHL). The clinical results of patients with SSNHL treated with IT-DEX are not always consistent with the apical-basal gradient pattern of concentration, even though it has been generally known that the treatment of SSNHL is dependent on the concentration of DEX. Unfortunately, there have been no reports of a tendency for improved hearing gains at high frequencies (basal turn). Therefore, we investigated the distribution pattern of DEX in the cochlea with the assistance of quantum dot-dexamethasone nanocomplex (QDDN). QDDNs were injected intratympanically into the bulla of Sprague-Dawley rats and the distribution of the QDDN in the cochlea was analyzed by fluorescence microscopy. From our in vivo animal study and statistical comparisons of clinical data, it was clearly observed that the concentration distribution of QDDN at the basal turn corresponds with the hearing improvement in patients with SSNHL, especially at 8000 Hz. These results of animal research are useful for further applications for treatment of human patients for SSNHL and are effective to determine the optimized dosages of DEX.