Published papers

Inner ear energy failure is associated with disorders such as inner ear ischemia. Recently, we used the mitochondrial toxin 3-nitropropionic acid (3-NP) to establish an animal model of inner ear energy failure that presents with auditory dysfunction. Here we investigated the mechanisms underlying balance disorders in the 3-NP animal model. Spontaneous nystagmus peaked 6 hr after treatment with either 300 mM or 500 mM 3-NP. The nystagmus attenuated gradually and disappeared 3 days after 3-NP treatment. A caloric test using ice water was performed to evaluate residual vestibular function 7 days after 3-NP treatment. The response to caloric stimulation was reduced to ∼40% of the response of the untreated ear following 300 mM 3-NP and was undetectable following 500 mM 3-NP. Structural changes in the peripheral vestibular organs were analyzed by light and electron microscopy. Severe loss of stereocilia was observed following 500 mM 3-NP, whereas disorganized and mildly reduced stereocilia were observed following 300 mM 3-NP. There was severe loss and degeneration of vestibular hair cells following 500 mM 3-NP but only slight loss and degeneration of hair cells following 300 mM 3-NP. These results indicate that acute inner ear energy failure causes balance dysfunction mainly by damaging hair cells in the vestibule, which is distinct from the mechanism underlying auditory disorders.

Hearing impairment can be the cause of serious socio-economic disadvantages. Recent studies have shown inflammatory responses in the inner ear co-occur with various damaging conditions including noise-induced hearing loss. We reported pro-inflammatory cytokine interleukin-6 (IL-6) was induced in the cochlea 6 h after noise exposure, but the pathophysiological implications of this are still obscure. To address this issue, we investigated the effects of IL-6 inhibition using the anti-IL-6 receptor antibody (MR16-1). Noise-exposed mice were treated with MR16-1 and evaluated. Improved hearing at 4 kHz as measured by auditory brainstem response (ABR) was noted in noise-exposed mice treated with MR16-1. Histological analysis revealed the decrease in spiral ganglion neurons was ameliorated in the MR16-1-treated group, while no significant change was observed in the organ of Corti. Immunohistochemistry for Iba1 and CD45 demonstrated a remarkable reduction of activated cochlear macrophages in spiral ganglions compared to the control group when treated with MR16-1. Thus, MR16-1 had protective effects both functionally and pathologically for the noise-damaged cochlea primarily due to suppression of neuronal loss and presumably through alleviation of inflammatory responses. Anti-inflammatory cytokine therapy including IL-6 blockade would be a feasible novel therapeutic strategy for acute sensory neural hearing loss.

Objectives: To determine the long-term prognosis of low-frequency hearing loss and predictive factors for the 10-year outcome of low-frequency hearing loss. Study Design: Case series with chart review. Setting: Tertiary referral center. Subjects and Methods: From 1979 to 1998, 466 consecutive patients with low-frequency hearing loss received initial treatment at the Hearing and Tinnitus Clinic of Keio University Hospital. Of the 49 eligible patients, pure-tone threshold data obtained over a period of 10 years after onset of low-frequency hearing loss were available for analysis. To determine the progression of hearing loss, we analyzed audiometric pattern changes. We also examined how the following factors affected 10-year prognosis: sex, age, side of hearing loss, accompanying dizziness, pre-therapeutic hearing thresholds at low frequencies, initial therapy results, and fluctuation of hearing during the first year after onset. Results: High- and pan-frequency hearing loss increased as time progressed. About half of the cases developed high- or pan-frequency hearing loss within 10 years of onset. Audiometric patterns measured at 10 years significantly correlated with those measured at one (r = 0.57), three (r = 0.73), and five years (r = 0.85). The 10-year prognosis significantly correlated with only two factors: initial therapy results (r = 0.49) and fluctuation of hearing during the first year (r = 0.43). Conclusions: About half of the cases in our study developed high- or pan-frequency hearing loss within 10 years of onset of low-frequency hearing loss. The initial therapy results and fluctuation of hearing during the first year may indicate the long-term prognosis of patients presenting with low-frequency hearing loss.

Objective: The objective of this study was to assess the clinical effectiveness of Traditional Chinese Medicine (TCM) as an adjuvant therapy for recurrent respiratory papillomatosis. Design: The design of this study was a case series. Location and subjects: Fifty-one (51) patients with laryngeal papillomatosis who were treated at Keio University Hospital between May 1981 and April 2008 were incorporated in this study. Interventions: Individually formulated TCM was orally administered postsurgically to 20 patients with aggressive laryngeal papillomatosis requiring multiple laser ablations (at least biannually) because of frequent recurrence. Eight (8) patients were excluded because of discontinued visits or medication (6 patients), or malignant transformation of the lesion (2 patients). The remaining 12 patients were enrolled in this study. Outcome measures: Retrospective chart review and review of the patients' recorded laryngeal images were performed. Clinical response to TCM was measured by the surgical necessity and Derkay's severity score for each patient, followed by statistical analyses. Results: Surgeries were required statistically less often (p= 0.0029) after TCM administration compared with the pre-TCM period. Furthermore, Derkay's severity score was significantly lower (p= 0.022) at the patients' last visit compared with the score before TCM administration. Conclusions: TCM may be a useful adjuvant therapy to treat aggressive laryngeal papillomatosis. Further studies are necessary to clarify the pharmacological mechanism of TCM in the treatment of laryngeal papillomatosis.

We evaluated the effects of a selective serotonin reuptake inhibitor, paroxetine, on treating tinnitus.Tinnitus patients stratified for the presence of depression and anxiety were studied retrospectively. Fifty-six patients were observed for more than 6 months. They were initially treated with paroxetine only at a dose of 10 mg/day for 2-4 weeks; thereafter, the dose was increased to 20 mg/day. Tinnitus distress was evaluated with the Tinnitus Handicap Inventory (THI) and with visual analog scales (VASs) for tinnitus loudness and annoyance. Depression and anxiety were measured with the Self-Rating Depression Scale (SDS) and the trait section of the State-Trait Anxiety Inventory (STAI). The patients were grouped according to their SDS and STAI scores, and each variable was compared at baseline and the 6-month follow-up. Changes among these variables were also examined to determine whether reduced tinnitus distress was related to the improvement of depression or anxiety. Patients with both depression and anxiety showed better results (decrease in THI, VASs, SDS and STAI scores) than patients with anxiety alone, or patients without depression and anxiety. In patients with depression and anxiety, changes in tinnitus variables and changes in depression and anxiety scores were strongly correlated. In other patients, however, changes in tinnitus variables and changes in depression and anxiety scores were not correlated. These results suggest that paroxetine is effective in treating distressed tinnitus patients with depression and anxiety by reducing their tinnitus severity as well as their depression and anxiety.

Introduction: Dural and anterior cranial base reconstruction is essential in the surgical resection of a craniofacial tumor that extends from the paranasal sinuses to the subdural space. Watertight reconstruction of vascularized tissue is essential to prevent postoperative liquorrhea, especially under conditions that prevent wound healing (e.g., postoperative irradiation therapy).Method: We successfully treated two cases of olfactory neuroblastoma by endoscopic-assisted craniotomy with primary dural closure and anterior cranial base reconstruction using a multi-layered flap technique. Dural defects were closed using temporal fascia or fascia lata in a conventional fashion, immediately after detaching the subdural tumor, in order to isolate and prevent contamination of subdural components and cerebrospinal fluid (CSF) from the tumor and nasal sinuses. Tumor removal and anterior cranial base reconstruction were performed without any concern of CSF contamination after dural closure by craniotomy and endoscopic endonasal approach (EEA). Vascularized pericranial flaps (PCF) and nasoseptal flaps (NSF) were used simultaneously as doubled-over layers for reconstruction.Results: The tumor was completely removed macroscopically and the anterior cranial base was reconstructed in both cases. CSF leak and postoperative meningitis were absent. Postoperative and irradiation therapy courses were successful and uneventful.Conclusions: This multi-layered anterior cranial base reconstruction consisted of three layers: a fascia for dural plasty and double-layered PCF and NSF. This surgical reconstruction technique is suitable to treat craniofacial tumors extending into the subdural space through the anterior cranial base dura mater.

We retrospectively reviewed the records of the 30 patients with adenoid cystic carcinoma of the head and neck (ACCHN) who had undergone initial treatment in the Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine between 1988 and 2007. The primary tumor site was the parotid gland in 10 patients and the submandibular gland in 4 patients, which account for about a half of the subjects. Thirty patients underwent surgical resection with curative intent as the primary treatment, of which 10 patients had post-operative radiotherapy. The 5- and 10-year disease-specific survival (DSS) was 73.9% and 62.4%, respectively, whereas the 5- and 10-year disease-free survival (DFS) was 64.3% and 59.7%, respectively. A univariate analysis revealed that DSS was significantly correlated with perineural invasion (p = 0.010) and lymphatic invasion (p = 0.036), while DFS was significantly correlated with higher T-stage (p = 0.044), a positive surgical margin (p = 0.012) and perineural invasion (p = 0.019). A multivariate analysis demonstrated that perineural invasion (/> = 0.034, risk ratio = 9.530) was the independent prognostic factor for DSS, whereas for DFS it was a positive surgical margin (p = 0.038, risk ratio = 8.897). The histological grade classification, defined specifically for ACC, showed no correlation with the survival. Extended resection with wider margin and additional resection in cases with positive margin may improve treatment results, however, surgical resection alone can prevent neither the development of local recurrence mainly attributed to undetectable perineural invasion, nor that of delayed distant, metastasis. Therefore, the roles of adjuvant radiotherapy and effective systemic therapies are also significant in ACCHN, although a reliable regimen for the latter has not yet been established. Development of a personalized strategy for the adjuvant therapy, which should be based on the accurate prediction of the long-term prognosis in combination with dependable molecular biomarkers, would be indispensable in the future to improve the clinical outcome of the patients with ACCHN.

We have previously reported on the effects of tinnitus retraining therapy (TRT) involving monaural noise generators (NGs) up to 24 months after the start of treatment (Eur Arch Otorhinolaryngol. 2013 Feb; 270(2): 443-8.) but very few reports exist about the long-term effects of TRT for periods of over 2 years. The aim of this study was to report the effects of TRT involving monaural NGs more than 24 months after the start of treatment. Thirty-three patients with chronic tinnitus were included in this study. All received directive counseling and monaural NGs without any other combination treatment. Effects were evaluated with the Tinnitus Handicap Inventory (THI) at their final visits to our clinic (average 31 months after the start of treatment). The average THI scores significantly improved from 55.3 ± 19.7 at baseline to 33.5 ±23.3 at their final visits. Seventeen patients (52%) improved by more than 20 points from the baseline. Eleven patients who were treated with TRT for more than 3 years were individually observed in a detailed manner. Some of them experienced aggravation of their symptoms after 2 years' successful treatments. This study suggests that, although TRT seems effective more than 2 years after the start of treatment, the clinical course of each patient can vary and we need to follow them periodically depending on their situations and symptoms.

Patients with Ménière's disease who have relapsed following endolymphatic sac surgery (EDS) or intratympanic gentamicin injection are occasionally treated with intratympanic gentamicin injections or revision surgery. However, there is a potential link between Ménière's disease and anxiety or depression. The use of serotonin selective reuptake inhibitors (SSRIs) is likely be beneficial in the treatment of patients with Ménière's disease. The aim of this report is to describe the benefits of SSRIs in patients with relapsed Meniere's disease. Over the course of two years, three patients were treated for symptoms associated with Ménière's disease with an SSRI (sertraline), with the complete resolution, or significant improvement, of symptoms. In these cases, the SSRI may have treated the associated morbidity and not Ménière's disease itself. Ménière's disease that appears to be resistant to typical otological treatment may not be just Ménière's disease. Ménière's disease may co-exist with three other conditions that are able to cause vestibular symptoms and respond to SSRIs: migraine-associated vertigo (MAV), panic disorders and chronic subjective dizziness (CSD).

When a thyroid nodule has malignant features found by some examinations (e.g. Echo, FNAC, CT), we perform surgical resection. But if the thyroid nodule does not have malignant feature, there is still the possibility of malignancy, especially when the nodule is large. In the case of large pre-operatively benign thyroid nodules, we therefore consider a diagnostic lobectomy. There is, however, no definite recommendation how large a nodule should be before a lobectomy is performed, and how many malignancies exist in pre-operatively benign nodules. In our hospital, we consider surgical resection when the diameter of the thyroid nodule is over 3 cm. In this study, we analyze pre-operatively benign thyroid nodules in which surgical resection was performed in our hospital, how many malignant nodules there were and what the characteristics were between benign or malignant nodule. From 2005 April to 2012 June, 351 patients underwent a lobectomy in our hospital, 70 of which were pre-operatively benign thyroid nodules with diameters of over 3 cm. We analyzed the pathological findings and compared the nodule diameters, serum thyroglobulin, FNAC's classification and some characteristics of echography between pathologically benign and malignant cases. Fifty-eight patients (83%) had pathologically benign nodules, and 12 patients (17%) had malignant nodules. In 58 benign nodules, 33 nodules (47%) were adenomatous goiter, 24 patients (34%) had follicular adenomas and 1 nodule (1%) was an atypical adenoma. In the 12 malignant patients, 8 patients (11%) had papillary adenocarcinoma and 4 patients (6%) had follicular adenocarcinoma. Almost no significant characteristics were found concerning malignancy, in diameter, serum thyroglobulin, class of FNAC and features of echography. As for complications after surgery, hypothyroidism occured in 4 patients (6%), and neither hypoparathyroidism nor vocal fold paralysis occurred. We concluded that pre-operatively benign thyroid nodule that were over 3 cm in diameter had about a 17% possibility of malignancy. Examinations may not distinguish whether such pre-operatively benign tumors are benign or malignant before surgical resection. We should therefore consider whether to perform therapeutic surgery or not in such patients.

The inner ear was previously assumed to be an "immune-privileged" organ due to the existence of its tight junction-based blood-labyrinth barrier. However, studies performed during the past decade revealed that the mesenchymal region of the cochlea, including its lateral wall, is a common site of inflammation. Neutrophils do not enter this region, which is consistent with the old dogma; however, bone marrow-derived resident macrophages are always present in the spiral ligament of the lateral wall and are activated in response to various types of insults, including noise exposure, ischemia, mitochondrial damage, and surgical stress. Recent studies have also revealed another type of immune cell, called perivascular melanocyte-like macrophages (PVM/Ms), in the stria vascularis. These dedicated antigen-presenting cells also control vascular contraction and permeability. This review discusses a series of reports regarding inflammatory/immune cells in the cochlear lateral wall, the pathways involved in cochlear damage and their potential as therapeutic targets.

A 68-year-old woman presented dizziness whenever she put her finger into the right ear and also complained of water-streaming tinnitus, which indicated she would have been suffering from perilymph fistula. An exploratory tympanotomy was conducted. Leakage of perilymph from the round window was suspected, although the cochlin-tomoprotein (CTP) results were negative. After the procedure, the patient’s finger-induced dizziness, tinnitus, and vertigo spells disappeared completely. However, her dizzy symptom did not improve. The patient also complained of general fatigue, weight loss, and insomnia, which led us to suspect comorbid depression. Antidepressants and vestibular rehabilitation treatment resulted in a significant improvement in her dizziness. Although it is not apparent whether the patient had a perilymph fistula, this case demonstrates the importance of evaluating not only physical symptoms but also psychological comorbidity, especially when the physical symptoms are intractable despite treatment.

Objectives/Hypothesis To investigate possible association of hearing loss and SLC26A4 mutations with the subgroups of enlarged vestibular aqueduct (EVA) morphology in Japanese subjects with hearing loss. Study Design Retrospective multicenter study. Methods Forty-seven subjects who had vestibular aqueduct with midpoint diameter >1 mm by computed tomography of the temporal bone were enrolled at multiple sites across Japan, and DNA samples and clinical data were collected. EVA morphology was classified into four subgroups by the pattern of enlargement: aperture, aperture and midpoint, midpoint, and borderline enlargement. Venous blood DNA samples were subjected to polymerase chain reaction-based direct sequencing of all exons and exon-intron boundaries of the SLC26A4. Results Four novel SLC26A4 mutations were identified in the present study. SLC26A4 mutations were detected in almost all subjects with aperture, aperture and midpoint, and midpoint enlargement. In contrast, 71% of subjects with borderline enlargement had no SLC26A4 mutation. No significant difference was found in the distribution of truncating and nontruncating SLC26A4 mutations between the EVA subgroups. In addition, no significant correlation was observed between the EVA subgroups and hearing levels, incidence of hearing fluctuation, or progression of hearing loss. Conclusions Subgroups of EVA morphology were significantly correlated with the presence or absence of SLC26A4 mutation. In a subgroup analysis of subjects with SLC26A4 mutations, however, differences in the EVA subgroups were not correlated with SLC26A4 genotypes or characteristics of hearing loss. Level of Evidence NA. Laryngoscope, 124:E134-E140, 2014

The surgical results of 18 cases of clival/upper cervical chordoma treated in the last decade via the endoscopic endonasal approach (EEA, 9 cases) and the transoral-transpalatal approach (TO-TPA, 9 cases) were compared. Each group showed the same incidence of subdural invasion, with 5 cases each. The superior (frontal base) and lateral surgical fields were wider by EEA, but the inferior view lower than the cranio-vertebral junction (CVJ) was wider by TO-TPA. Gross total removal was achieved in 3 cases in the EEA group, but in only 1 case in the TO-TPA group. Differences in radicality might be due to the extent of the lateral and subdural overview. However for large tumors extending below the CVJ, TO-TPA was the only viable approach for surgical removal. Surgical complications were higher in the EEA (4 cases) than the TO-TPA group (1 case), and were mainly caused by aggressive management of subdural invasion in the EEA group. Post-operative oral intake was earlier and the operative time was shorter in the EEA group. The surgical results were more radical and less invasive in the EEA group than the TO-TPA group. However in tumors extending below the CVJ, the surgical field in EEA was limited, indicating the need to use the transoral route or a combination of routes. A higher complication rate following subdural management was a negative factor that requires improvement in the EEA group and two-staged EEA followed by a transcranial approach may be considered for the cases with subdural invasion.

The aim of this study was to analyze the bacterial flora in the nasal cavity and sphenoid sinus and evaluate the sensitivity of these bacteria to antibiotics that can be used to prevent postoperative meningitis. Bacteria of the preoperative nasal cavity and intraoperative sphenoid sinus mucosa were cultured and analyzed in 40 patients (20 men and 20 women; mean age, 52.2 years) who underwent endoscopic transsphenoidal surgery. The sensitivity of these bacteria to cephalosporin, a representative prophylactic antibiotic, was examined. Staphylococcus epidermidis was the most frequently detected species in both spaces; 24 (38.7%) of 62 isolates in the nasal cavity and 26 (37.1%) of 70 isolates in the sphenoid sinus. In contrast, Corynebacterium species were found mainly in the nasal cavity, and anaerobic bacteria were found only in the sphenoid sinus. Bacteria that were resistant to cephalosporin were found in the nasal cavity in 3.2% of patients and in the sphenoid sinus in 20% of patients. In conclusion, the composition of bacterial flora, including bacteria that are resistant to prophylactic antibiotics, differs between the nasal cavity and the sphenoid sinus.

Conclusion: An epidemiological survey of hospitals and private clinics in Japan regarding idiopathic sudden sensorineural hearing loss (SSNHL) revealed that the incidence of SSNHL was 60.9 per 100 000 population. There were more females than males in the younger generation. Objective: The incidence of SSNHL varies largely by country. Because the Japanese criteria for diagnosing SSNHL have changed in accordance with those widely used in other parts of the world, a clinicoepidemiological study was undertaken using the new criteria. Methods: Ehime, Aichi, and Iwate Prefectures were selected from the western, central, and northeastern regions of Japan, respectively. The subjects for this study were patients who suffered SSNHL between April 1, 2012 and March 31, 2013. Questionnaires were mailed to all hospitals and private clinics in which ENT doctors were working. Initial and final audiograms were requested for 10% of the patients. Results: In all, 78 of 90 hospitals (87%) and 303 of 407 private clinics (74%) responded. It was reported that 1663 patients visited hospitals and 3090 patients visited only private clinics. It was estimated that 6205 SSNHL patients visited hospitals or private clinics in 1 year from a population of 10 145 000. Also, 23% of patients suffered acute low-tone SNHL (female to male ratio; 3:1 in definite cases).

Objectives: We used hearing tests and peripheral blood sample analyses to characterize the pathology of idiopathic sudden sensorineural hearing loss (ISSNHL) and to identify possible prognostic factors for predicting recovery of hearing loss. Study Design: A retrospective, multicenter trial was conducted. Methods: Two hundred three patients examined within 7 days after the onset of ISSNHL received prednisone with lipoprostaglandin E1. Pure-tone auditory tests were performed before and after treatment with these drugs. Blood tests were performed on blood samples collected during the patients' initial visit to our clinic. Results: In all patients, elevated white blood cell (WBC) counts, fasting blood sugar levels, HgbA1c, and erythrocyte sedimentation rate (ESR) significantly correlated with high hearing threshold measurements obtained on the initial visit. High fibrinogen levels, WBC counts, ESR, and low concentrations of fibrinogen degradation products (FDP) were associated with lower hearing recovery rates. Additionally, different audiogram shapes correlated with different blood test factors, indicating that different pathologies were involved. Conclusions: High fibrinogen levels measured within seven days after ISSNHL onset correlated with poorer hearing recovery. This may be a consequence of ischemia or infections in the inner ear. The high WBC counts also observed may therefore reflect an immune response to inner ear damage induced by ischemic changes or infections. Our data indicate that therapeutic strategies should be selected based on the timing of initial treatment relative to ISSNHL onset.

Background: The epithelial-to-mesenchymal transition (EMT) accompanied by the downregulation of E-cadherin has been thought to promote metastasis. Cyclooxygenase-2 (Cox-2) is presumed to contribute to cancer progression through its multifaceted function, and recently its inverse relationship with E-cadherin was suggested. The aim of the present study was to investigate whether selective Cox-2 inhibitors restore the expression of E-cadherin in head and neck squamous cell carcinoma (HNSCC) cells, and to examine the possible correlations of the expression levels of EMT-related molecules with clinicopathological factors in HNSCC. Methods. We used quantitative real-time PCR to examine the effects of three selective Cox-2 inhibitors, i.e., celecoxib, NS-398, and SC-791 on the gene expressions of E-cadherin (CDH-1) and its transcriptional repressors (SIP1, Snail, Twist) in the human HNSCC cell lines HSC-2 and HSC-4. To evaluate the changes in E-cadherin expression on the cell surface, we used a flowcytometer and immunofluorescent staining in addition to Western blotting. We evaluated and statistically analyzed the clinicopathological factors and mRNA expressions of Cox-2, CDH-1 and its repressors in surgical specimens of 40 patients with tongue squamous cell carcinoma (TSCC). Results: The selective Cox-2 inhibitors upregulated the E-cadherin expression on the cell surface of the HNSCC cells through the downregulation of its transcriptional repressors. The extent of this effect depended on the baseline expression levels of both E-cadherin and Cox-2 in each cell line. A univariate analysis showed that higher Cox-2 mRNA expression (p = 0.037), lower CDH-1 mRNA expression (p = 0.020), and advanced T-classification (p = 0.036) were significantly correlated with lymph node metastasis in TSCC. A multivariate logistic regression revealed that lower CDH-1 mRNA expression was the independent risk factor affecting lymph node metastasis (p = 0.041). Conclusions: These findings suggest that the appropriately selective administration of certain Cox-2 inhibitors may have an anti-metastatic effect through suppression of the EMT by restoring E-cadherin expression. In addition, the downregulation of CDH-1 resulting from the EMT may be closely involved in lymph node metastasis in TSCC.

Cochlear lateral wall has recently been reported as a common site of inflammation, yet precise molecular mechanisms of the inflammatory responses remain elucidated. The present study examined the inflammatory responses in the lateral wall following acute mitochondrial dysfunction induced by a mitochondrial toxin, 3-nitropropionic acid (3-NP). Reverse-transcription (RT)-PCR revealed increases in the expression of the proinflammatory cytokines interleukin (IL)-1β and IL-6. Immunohistochemistry showed an increase in the number of activated cochlear macrophages in the lateral wall, which were in close proximity to IL-6-expressing cells. A genome-wide DNA microarray analysis of the lateral wall revealed that 35% and 60% of the genes showing >2-fold upregulation at 1 d and 3 d post-3-NP administration, respectively, were inflammatory genes, including CC- and CXC-type chemokine genes. High expression of CCL-1, 2, and 3 at 1 d, and of CCL-1, 2, 3, 4, and 5, CCR-2 and 5, and CX3CR1 at 3 d post-3-NP administration, coupled with no change in the level of CX3CL1 expression suggested that macrophages and monocytes may be involved in the inflammatory response to 3-NP-mediated injury. Quantitative (q)RT-PCR showed a transient induction of IL-1β and IL-6 expression within 24 h of 3-NP-mediated injury, followed by sustained expression of the chemoattractants, CCL-2, 4 and 5, up until 7 d after injury. The expression of CCL-2 and IL-6 was higher in animals showing permanent hearing impairment than in those showing temporary hearing impairment, suggesting that these inflammatory responses may be detrimental to hearing recovery. The present findings suggest that acute mitochondrial dysfunction induces secondary inflammatory responses in the lateral wall of the cochlear and that the IL-6/CCL-2 inflammatory pathway is involved in monocyte activation. Therefore, these secondary inflammatory responses may be a potential post-insult therapeutic target for treatments aimed at preventing the damage caused by acute mitochondrial dysfunction in the cochlear lateral wall.