Safety of Intracochlear Dexamethasone injection through Round Window Membrane in Guinea Pigs

Abstract

Background: Delivering drugs to the cochlea is challenging due to its complex anatomical structure, almost entirely encased in bone. Intratympanic steroid injections are commonly used for inner ear conditions like Meniere’s disease and sudden sensory-neural hearing loss, but they have limitations, including rapid clearance via the Eustachian tube and the need for patients to remain in a supine position post-injection. Intracochlear drug delivery bypasses these limitations, offering potential for more effective treatment.

Objective: This study aims to assess the safety and histopathological effects of intracochlear dexamethasone administration via microneedle through the round window membrane (RWM) in guinea pigs.Methods: Using a Hamilton syringe, 5 µl of dexamethasone sodium phosphate was administered through the RWM into the cochlea of guinea pigs. Animals were observed for six weeks, then euthanized for histopathological analysis. The cochlear specimens were examined for inflammation, fibrosis, neo-ossification, hair cell counts, and spiral ganglion neuron density, comparing the treated ear to the untreated ear as a control.

Results: Histopathological analysis showed no signs of acute or chronic inflammation, fibrosis, or neo-ossification in the treated cochleae. There were no significant differences in hair cell or spiral ganglion neuron densities between treated and control cochleae.

Conclusion: Intracochlear dexamethasone injection via microneedle is a safe, minimally invasive approach for direct cochlear drug delivery, showing no long-term histopathological changes. Microneedles hold promise for targeted treatments in inner ear diseases with minimal anatomic or physiological disruption.