Background/Objectives: Frequency-to-place mismatch between cochlear implant (CI) electrodes and cochlear tonotopy has been suggested to affect postoperative speech perception. This study aimed to examine the associations between frequency-to-place mismatch and speech perception outcomes across multiple linguistic levels in patients with CI and to assess how these associations change over time using postoperative computed tomography. Methods: This retrospective cohort study included 44 postlingually deafened adults who underwent unilateral cochlear implantation with a Flex28 electrode by a single surgeon at a tertiary care hospital. Speech perception was assessed using CI-2004, a Japanese speech perception test consisting of monosyllables, consonants, words, and sentences, in quiet settings at 3, 6, and 12 months after CI activation. Partial correlation analyses between frequency-to-place mismatch and postoperative speech perception scores were performed in 35 of the 44 patients, controlling for age and mean preoperative pure-tone thresholds. Results: Negative associations were observed between frequency-to-place mismatch and CI-2004 scores, particularly for monosyllable and consonant perception in uncorrected analyses. After correction for multiple comparisons, only consonant perception at 3 months after CI activation remained significant (r = −0.52, p = 0.002). Similar patterns were observed for other speech measures and at later time points, although these did not remain significant after correction. Conclusions: Frequency-to-place mismatch was associated with postoperative speech perception outcomes, particularly those involving phoneme-level recognition. After correction for multiple comparisons, only consonant perception at 3 months after CI activation remained significant.

Hypothesis: This study aimed to evaluate the effectiveness of a less invasive drug delivery device, the pyro-drive jet injector-intratympanic (PJI-IT), as an alternative to the conventional intratympanic injection (ITI). Background: Conventional ITI using fine needles can cause damage to the tympanic membrane and hearing loss. A safer, less invasive delivery platform would be valuable for the local treatment of inner-ear disorders. Methods: Lipid nanoparticles (LNPs) containing firefly luciferase (Fluc) mRNA were injected into the middle ears of male guinea pigs (n=30) using the needle-free PJI-IT, which created a small, temporary perforation of the tympanic membrane through a high-pressure liquid jet. Conventional fine [30-gauge (30G)] needle injection was used as control. Perforation size and closure time were measured microscopically. Bioluminescence imaging was performed to evaluate Fluc protein production. Auditory brainstem responses (ABRs) were recorded before and after the injection to assess auditory function. Results: The PJI-IT and the 30G needle provided comparable amounts of Fluc protein in the tympanic cavity and cochlea. Compared with the conventional needle, the PJI-IT caused a smaller perforation of the tympanic membrane, which was closed faster. Auditory function was virtually preserved after injection using the PJI-IT, whereas injection using the conventional fine needle induced significant ABR threshold elevations. Conclusions: The PJI-IT has the potential to be a safe and minimally invasive instrument for intratympanic injections. The preserved auditory function and rapid healing of the perforated tympanic membrane suggest its clinical availability, especially for the repeated administration of biological agents such as mRNA regenerative medicine.

Objectives: The middle cranial fossa (MCF) approach is valued for preserving hearing while accessing the internal auditory canal (IAC), petrous apex, inner ear, and related structures. This study evaluated its clinical outcomes across otolaryngological diseases, focusing on postoperative complications, hearing preservation, and the effect of IAC manipulation on auditory function. Methods: We retrospectively analyzed 35 patients who underwent MCF otologic surgery at a single center over twelve years. We calculated the proportion of MCF cases among all otologic surgeries and assessed postoperative complications and hearing changes (bone conduction thresholds). Outcomes were compared between patients with and without IAC manipulation. Results: MCF procedures comprised 1.4% of all otologic surgeries. Petrous bone cholesteatoma was the leading indication (15 cases). Intracranial complications occurred in 4 patients (11.4%): seizures, epidural abscess, and cerebral infarction. Facial nerve paralysis occurred in 3 (10.7%) patients without any cerebrospinal fluid leaks. In patients without IAC manipulation, hearing functions were preserved (22.3 ± 7.8 dB HL pre- vs. 25.7 ± 9.5 dB HL postoperatively), whereas those with IAC manipulation showed significantly greater deterioration. Conclusions: The middle cranial fossa approach, though technically demanding and infrequently used, offers a safe and effective option across various otolaryngological diseases. This approach achieved favorable hearing preservation with a low complication rate, particularly when intradural manipulation of the IAC was not required.