First- and second-order sensory neurons of the ascending auditory pathway, located in the spiral ganglion and the cochlear nucleus (CN), respectively, participate in the olivocochlear reflex, which protects hair cells from acoustic overstimulation. The KCNQ4 channel is expressed in the organ of Corti and has also been detected in the CN. In knock-out (KO) mice for KCNQ4, sensory cells and spiral ganglion neurons degenerate with age, while the impact of KCNQ4 deletion on the CN remains unknown. Therefore, we analyzed the structural integrity of the CN at middle age in KO animals. We examined the expression of the neuronal KCNQ channel subunits in the CN by RNA isolation, followed by qPCR. KCNQ3 expression was significantly increased (p=0.0418) in KO mice compared to WT animals at young age, suggesting changes in the excitability of CN neurons. In addition, we assessed microglial status in the CN of middle-aged KO mice by brain cryosectioning, followed by immunohistochemical analysis of the microglial marker Iba1. Confocal microscopy revealed a notable increase in the fluorescence intensity (p=0.0013) and in the number of microglial cells from 0.29 to 0.86 cells/µm2 (p<0.0001) within the CN of KO mice compared to WT. This finding suggests alterations in neuronal excitability and enhanced microglial reactivity, potentially associated with neuroinflammatory processes that may contribute to neuronal loss in aged animals.