Three months to 5 years follow-up of 21 patients were accomplished by pure tone audiometry and other details. There was no recurrent cholesteatoma in the patients. Compared with pre-operative average bone conduction at 0.5, 1, 2, 4, and 8 kHz, 12 cases had a difference less than 5 dB, three patients' hearing improved (more than 10 dB), and five cases declined (more than 10 dB). One patient received cochlear implantation 3 months after the surgery. The average bone and air conduction thresholds at 0.5, 1, 2, 4, and 8 kHz had no obvious change (p > 0.05) in 11 patients managed by a canal wall down mastoidectomy with tympanoplasty.
The spiral ganglion neurons (SGNs) are the primary afferent neurons in the spiral ganglion (SG), while their degeneration or loss would cause sensorineural hearing loss. As a cardiac-derived hormone, atrial natriuretic peptide (ANP) plays a critical role in cardiovascular homeostasis through binding to its functional receptors (NPR-A and NPR-C). ANP and its receptors are widely expressed in the mammalian nervous system where they could be implicated in the regulation of multiple neural functions. Although previous studies have provided direct evidence for the presence of ANP and its functional receptors in the inner ear, their presence within the cochlear SG and their regulatory roles during auditory neurotransmission and development remain largely unknown. Based on our previous findings, we investigated the expression patterns of ANP and its receptors in the cochlear SG and dissociated SGNs and determined the influence of ANP on neurite outgrowth in vitro by using organotypic SG explants and dissociated SGN cultures from postnatal rats. We have demonstrated that ANP and its receptors are expressed in neurons within the cochlear SG of postnatal rat, while ANP may promote neurite outgrowth of SGNs via the NPR-A/cGMP/PKG pathway in a dose-dependent manner. These results indicate that ANP would play a role in normal neuritogenesis of SGN during cochlear development and represents a potential therapeutic candidate to enhance regeneration and regrowth of SGN neurites.
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