Sun O Chang

Intravenous administration of human mesenchymal stem cells after noise- or drug-induced hearing loss in rats

Abstract Conclusion: Systemic application of human mesenchymal stem cells (hMSCs) may be another effective tool for stem cell supply to the inner ear. Objectives: Most researchers have used local application to provide the inner ear with stem cells. In spite of their efficacy, these methods can potentially cause irreversible damage to the inner ear. A homing phenomenon of systemically administered MSCs to the ischemic myocardium and brain was recently reported. Moreover, hMSCs have several advantages over conventional neural or embryonic stem cells. Thus we hypothesized that intense noise or ototoxic injury to the cochlea could induce the homing of hMSCs. Methods: We harvested hMSCs from bone marrow of the iliac crest of five normal individuals. Then hMSCs at a dose of 4 × 106 cells were given via intravenous injection of cell suspension into rats with cochleae damaged by noise or ototoxic drugs. Histological analysis was undertaken 30 days later. Results: Systemically delivered hMSCs were usually largely entrapped in the lungs. However, we documented the homing of some hMSCs to the cochlea with degenerated inner hair cells. The recruitment of hMSCs was limited to the spiral ganglion area only. The migration of donor cells into the cochlea was accompanied by the expression of brain-derived neurotrophic factor (BDNF).

Clinical characteristics of patients with narrow bony cochlear nerve canal: is the bilateral case just a duplicate of the unilateral case?

To evaluate whether there is a genetic contribution to the development of narrow bony cochlear nerve canal and analyze the differences between unilateral and bilateral narrow bony cochlear nerve canal.

Role of surgical management in temporal bone fibrous dysplasia.

Conclusion: Surgical treatment of fibrous dysplasia of the temporal bone (TBFD) revealed relatively good outcomes. Also, active surgical intervention is necessary to prevent the formation of secondary cholesteatoma or other complications. In particular, FD involving the inner ear may require greater caution when deciding on the resection area and timing of surgery. Objectives: The purpose of this study was to analyze clinical manifestations of TBFD and its surgical outcomes. Patients and methods: Nine patients diagnosed with TBFD after surgery at three tertiary referral centers were included. Pre- and postoperative clinical, audiological, and radiological findings were analyzed retrospectively. Results: Most patients (88.9%) showed FD involving the mastoid and adjacent area. Radiological patterns consisted of six pagetoid and three sclerotic forms; seven patients were monostotic, whereas two patients were polyostotic. Canalplasty (CP) was performed in six cases and intact canal wall mastoidectomy was performed in three of them; hearing gain was achieved in five and one patient maintained preoperative normal hearing. Two patients underwent revision CP and showed no recurrence. In addition, one case had secondary cholesteatoma formed by an obstruction of the external auditory canal; another with a fast-growing cystic mass in the petrous bone underwent transmastoid labyrinthectomy and had no recurrence for 11 months.

Facial nerve aberrations encountered during cochlear implantation.

Abstract Conclusion: In patients with cochleovestibular malformations, surgeons should always consider the possibility of an aberrant course or shape of the facial nerve (FN). In our series, the majority of cases could be successfully implanted without major complications through careful handling of the FN and ossicles. Objectives: To assess the frequency, type, and surgical implications of FN aberrations encountered during cochlear implantation (CI). Methods: Medical records and radiologic findings of 972 patients who underwent CI from 1988 to 2009 were reviewed retrospectively. Radiologic and intraoperative findings demonstrating malformations of the FN, ossicles, and inner ear were evaluated. Intraoperative events and postoperative FN outcome were reviewed. Results: Seven patients (0.7%) had an aberrant course or shape of the FN during CI. All these patients were pediatric. Four showed abnormal anterior or inferior location of the vertical segment, two had a bifurcated horizontal or vertical segment, and one had an inferiorly located horizontal segment. All seven patients displayed combined malformations of the cochlea and had malformed or missing ossicles. CIs were successfully performed via the facial recess approach and cochleostomy. There was no postoperative FN paralysis except in one case with immediate iatrogenic FN paralysis that recovered completely 1 month after FN decompression.

Changes in P2Y4 receptor expression in rat cochlear outer sulcus cells during development.

Extracellular adenosine triphosphate (ATP) released from cellular sources plays an important role in variety of the cochlear physiologic processes. The primary purinergic receptor subtype in the cochlea is the P2X2 receptor, which is a subtype of P2X receptor. This receptor appears to mediate a protective decrease in the electrical driving force in response to acoustic overstimulation. Outer sulcus cells (OSCs) in the cochlear lateral wall appear to maintain an adequate K+ concentration in the cochlear endolymph in response to varying intensities of auditory stimulation. However, little is known about developing OSCs. The purpose of this study was to investigate subtypes of purinergic receptors in developing rat OSCs using a voltage-sensitive vibrating probe. Results showed that only two P2 receptors (P2Y4 and P2X2) contributed to the regulation of short circuit currents in neonatal OSCs. ATP increased cation absorption via apical nonselective cation channels after activating P2Y4 receptors in early neonatal OSCs. P2Y4 expression rapidly declined postnatally and reached near adult levels on postnatal day 14. P2X2 was co-expressed with P2Y4 in early neonatal OSCs. Temporal changes in P2Y4 during OSC development might be involved in the establishment of the endolymphatic ion composition needed for normal auditory transduction and/or specific cellular differentiation.

Continuity of the incudostapedial joint: a novel prognostic factor in postoperative hearing outcomes in congenital aural atresia

Abstract Conclusion: Mean incudostapedial joint (ISJ) angulation of atretic ears was statistically wider than ISJ angulation of non-atretic ears. Postoperative hearing results in the narrow tympanoplasty type II (T2) subgroup were better than those in the wide T2 subgroup. In cases of abnormally wide ISJ angulation, we recommend that partial ossicular reconstruction (POR) be used as a surgical means of achieving hearing improvement. Objective: To report the results of ISJ angulation in patients with congenital aural atresia and its effects on postoperative hearing improvement. Methods: Patients undergoing canaloplasty with T2 (149 ears) and canaloplasty with POR (32 ears) were enrolled. The T2 group was dichotomized according to an ISJ cut-off of an angle of 120° into the ‘narrow’ T2 and ‘wide’ T2 subgroups. The pre- and postoperative air–bone gap (ABG) and ABG change were analyzed. Results: Mean ISJ angulation of non-atretic ears was 93.06 ± 13.21° and that of atretic ears in the T2 group was 118.39 ± 19.60° (p < 0.001). Mean short- and long-term postoperative ABGs were better in the narrow T2 subgroup than in the wide T2 subgroup (p = 0.01 and 0.03, respectively). The short-term postoperative ABG and ABG change in the POR showed superior results to those of the wide T2 subgroup (p < 0.001 and 0.041, respectively).

Surgical management options and postoperative functional outcomes of petrous apex cholesteatoma

Abstract Conclusion: In cases of petrous apex (PA) cholesteatoma, radical removal should be prioritized over an unreasonable sparing of hearing or facial symmetry. Nevertheless, for patients with serviceable hearing and spared inner ear structures, conservative approaches may be applicable. Restoration of facial nerve (FN) function is achievable by reanimation procedures. Objectives: To analyze clinical manifestations, surgical techniques, and postoperative functional results of PA cholesteatoma. Methods: From 1987 to 2010, 13 cases of PA cholesteatoma underwent operations. Clinical, audiological, and radiological findings, surgical approach, and postoperative functional outcomes were analyzed retrospectively. Results: The most common symptoms were hearing loss and FN paralysis. All PA cholesteatomas extended to the middle ear; 10 (76.9%) through the anterior-superior route, whereas the other 3 (23.1%) were through the posterior-superior route. In 10 patients, labyrinthectomy was inevitable because of inner ear invasion. However, three limited cholesteatomas were removable via the middle cranial fossa or transmastoid approach without changing the bone-conduction threshold. Among six cases with FN paralysis, one underwent interposition graft, two FN decompression, and the others hypoglossal-FN anastomosis. One FN decompression case recovered to House-Brackmann grade I, and all other reanimation cases finally presented with grade IV. There were no major complications or recurrences during the follow-up period.

KCNQ1/KCNE1 K+ channel and P2Y4 receptor are co-expressed from the time of birth in the apical membrane of rat strial marginal cells

Conclusion. KCNQ1/KCNE1 K+ channels and P2Y4 receptors are expressed in the apical membrane of rat strial marginal cells from postnatal day 1 (P1) and maintained throughout development. Objectives. The purpose of the present study was to investigate the developmental expression of KCNQ1/KCNE1 K+ channel and of P2Y4, which is an important metabotropic regulator of KCNQ1/KCNE1 K+ channel in strial marginal cells. Materials and Methods. Sprague-Dawley rats at different stages of development (P1, P3, P5, P7, P14, and P21) were studied. The spiral ligament with the stria vascularis was detached from the cartilaginous or bony cochlea and prepared for a voltage-sensitive vibrating probe and immunohistochemistry. Results. Chromanol 293B, a blocker of KCNQ1/KCNE1 K+ channel, inhibited short-circuit currents (Isc) from P1 to P21. Similarly, Isc were found to be decreased by uridine 5′-triphosphate at all ages. The antagonist profiles indicated that the apical P2Y receptor is P2Y4 subtype. KCNQ1, KCNE1, and P2Y4 were immunolocalized in the apical region of stria vascularis at P1.

Clinical observations and molecular variables of patients with hearing loss and incomplete partition type III

To analyze the clinical manifestations and genetic features of patients with hearing loss (HL) and incomplete partition (IP) type III malformation, and to evaluate speech performance after cochlear implantation (CI) in these patients.

Long term results of postoperative canal stenosis in congenital aural atresia surgery

Conclusion. Benefits of the use of anteriorly and inferiorly based periosteal flaps (AIPFs) in congenital aural atresia (CAA) patients was found to be effective at reducing canal stenosis (CS) occurrence by long term F/U. However, in terms of minimizing CS, in addition to recruitment of AIPFs, considerations of patient factors, such as degree of microtia and age are mandatory. Objectives. AIPF during canaloplasty were evaluated with a specific focus on whether this technique can offset the negative effects of several risk factors for postoperative CS after CAA surgery. Subjects and Methods. The authors undertook a retrospective review of the medical records of 164 congenital aural atresia patients (190 ears) who had undergone surgery at Seoul National University Hospital. Median follow up period was 54 months. The anterior approach surgical method with and without the use of AIPFs were utilized in 111 and 79 ears respectively. Comparison of the influences of several factors on CS occurrence was undertaken by statistical analyses to evaluate whether this AIPFs technique can counterbalance the negative effect of patient factors in postoperative CS. Results. Those with a younger age (<12 yrs), moderate to severe microtia (grade II, III), or those in whom AIPF was not used in surgery (non AIPF group) were found to show statistically significant higher frequency of CS(+). Nevertheless, the positive effect of AIPF was not able to completely counterbalance the effects of negative patient factors on CS development. A protocol compatible with the results of this study that minimizes CS is presented in the discussion.