FLUCTUATING HEARING LOSS AS A SYMPTOM OF ACQUIRED PERILYMPHATIC FISTULA (PLF) UNDER EXTERNAL INJURIES FACTOR.

OBJECTIVE: The aim: To evaluate the effectiveness of treatment patients with spontaneous PLF and labyrinthine window ruptures by studying the clinical and audiological results. PATIENTS AND METHODS: Materials and methods: 52 patients after exposure to traumatic factors in the anamnesis were evaluated. The perilymphatic fistula was diagnosed in 18 patients after the complex examination. All patients with PLF underwent surgical treatment. RESULTS: Results: Vestibular disorders and hearing loss were the predominant symptoms. The fistula test was positive in 11 (61%) patients. Fluctuating hearing loss was determined in 9 (50%) patients. Labyrinthine window ruptures were detected in 16 (88%) patients: oval window membrane rupture was identified in 6 patients, and in another 10 patients round window membrane rupture was found and was detected on CT scan. The surgical treatment included minimally invasive tympanotomy with combined microscopic and endoscopic visualization and sealing techniques. Results were evaluated in 6 months after surgical treatment, patients had a decrease in bone and air conduction thresholds at all evaluated frequencies and a significant decrease in the level of the air-bone interval. CONCLUSION: Conclusions: Fluctuating hearing loss is considered one of the key symptoms, which suggests the presence of PLF. Determination of PLF and its surgical treatment, by using minimally invasive tympanotomy with sealing technique using optimal combined visualization, allows obtaining a stable functional result, with hearing improvement and vestibular symptoms reducing.

Round window membrane rupture following blunt force trauma.

Round window rupture following barotrauma such as diving and air travel is well documented. However, we describe a case of round window rupture following a slap to the ear, which has not been described previously. A 12-year-old boy was slapped by his teacher in rural Nepal over his left ear and immediately noted hearing loss. There was no dizziness or tinnitus. He presented to our unit 21 days after the trauma and examination showed a perforation of the tympanic membrane in the anterior inferior quadrant with an otherwise normal ear examination and no nystagmus seen. Audiogram showed a left profound hearing loss, which was supported by auditory brainstem response test. Exploratory tympanotomy showed active perilymph leakage from the round window niche as demonstrated in the video attached. The round window was packed with cartilage and fascia to address the perilymph leakage. The patient was discharged the following day without any complications. This is an unusual cause for round window membrane rupture where the patient presented with hearing loss as his only symptom. Tympanotomy is recommended for patients with hearing loss following trauma with normal computed tomography imaging to exclude perilymph leak secondary to inner ear barotrauma.

Electrophysiological and histomorphological changes of cochlea in miniature pigs after abrasion of round window niches.

Background: In operations of cochlea implantation (CI), many surgeons choose to drill a window on the bone wall of cochlea basic rotation, when more and more patients receive CI with residual hearing, what damage this step would result in is unclear.Objective: To study the effect to inner ear hair cells which is caused by drilling during CI.Methods: 6 miniature pigs are equally divided into two groups, Round window niche of each pig in the experimental group was milled, while the pigs in control group wasn't. After implanting depth of 6.5, 11.5 and 20 mm, round window electrocochleography was recorded to analyze the change of cochlea microphonic (CM) potentials respectively, histomorphological changes was observed.Results: Thresholds of CM in experimental group were higher than that of control group at different depth, amplitudes were smaller. In further group, cilia of inner hair cells (IHC) at bottom rotation were significantly damaged. After operation, ABR hearing threshold of experimental group was higher, differences at low frequency region were more obvious.Conclusions: Damage caused by mulling round window niche may seriously affect the function of the hair cells. Damage of the IHC is greater than OHC. CI through round window may protect residual hearing.

CT and MRI for the diagnosis of perilymphatic fistula: a study of 17 surgically confirmed patients.

BACKGROUND: We evaluated the usefulness of CT and MRI for the diagnosis of perilymphatic fistula (PLF) of the round (RW) and/or oval (OW) windows, with surgery as gold standard. METHODS: We retrospectively enrolled 17 patients who presented a surgically confirmed PLF of the round (RW) or oval (OW) windows. All patients were imaged by CT + MRI (T2W SSFP without contrast) prior to surgery (= gold standard). Two radiologists, analyzed the RW and OW on the side of the clinical symptoms and sensitivity (Se) + Specificity (Sp) were calculated. RESULTS: Round window fistula was the most frequent (71%). The best sign of PLF on imaging was a fluid filling of the window niches, which had good Se (83-100% for RW, 66-83% for OW) and Sp (60% for RW, 91-100% for OW). Disorientation of the footplate and pneumolabyrinth were also only observed in 50% of OW PLF. CONCLUSION: The combination of CT and MRI is a reliable tool for a fast and accurate diagnosis of round and oval window perilymphatic fistula, with good sensitivity (> 80%). The most common sign of PLF on imaging is the presence of a fluid-filling in the RW (especially if > 2/3 of the RW niche) or in the OW niches on both CT and MRI. A disorientation of the footplate or the presence of a pneumolabyrinth are clearly in favor of an oval window perilymphatic fistula.

Surgical Outcomes on Hearing and Vestibular Symptoms in Barotraumatic Perilymphatic Fistula.

OBJECTIVE: To analyze surgical results on hearing and vestibular symptoms in patients with barotraumatic perilymphatic fistula (PLF) according to diagnostic criteria. METHODS: A total of 39 patients (41 ears) who underwent surgery on suspicion of barotraumatic PLF from January 2005 to December 2017 were included. Pure tone audiometry and videonystagmography (VNG) recording for spontaneous nystagmus and positional tests were performed preoperatively and postoperatively at 1 week and 1 month. Surgical outcomes were analyzed based on hearing results, subjective dizziness, and change of nystagmus. RESULTS: Preoperative hearing level was 75.5 ±â€Š28.7 dB for definite PLF and 88.5 ±â€Š22.8 dB for probable PLF, and levels were not significantly different between groups. Preoperatively, subjective dizziness was present in 18 (94.7%) and 19 (95%) in each group. Among 39 patients, 24 had VNG recordings. Positional nystagmus was recorded in 87.5% (7/8) and 87.5% (14/16) of the definite and probable PLF groups, respectively. Postoperatively, hearing was improved in 65% (13/20 ears) of definite PLF and 61.9% (13/21 ears) of probable PLF. There was no significant difference between the two groups. Hearing gain was significantly correlated with the time interval between symptom onset and surgical timing. Subjective dizziness was improved immediately after surgical repair in 97.4% (17/18) of definite PLF patients and 100% (19/19) of probable PLF patients. Even though dizziness was improved in most patients, some had persistent positional nystagmus and recurrent dizziness. CONCLUSIONS: Surgical sealing of both windows in suspected barotraumatic PLF is an effective treatment to improve hearing and subjective dizziness.

The effects of round window membrane injury and the use of a model electrode application on hearing in rats.

We conducted an animal experiment to investigate the effects of mechanical trauma to the round window with the placement of a model electrode inserted into the scala tympani on the cochlear reserve, and to determine the efficacy of topical steroids in preventing hearing loss in such a situation. Our subjects included 21 male Wistar albino rats that were assigned into three groups of 7 each. In all three groups, an initial mechanical injury to the round window was created. At that point, group 1 received no further treatment, group 2 received a dexamethasone injection into the cochlea, and group 3 underwent implantation of a multichannel cochlear implant guide followed by dexamethasone administration. After a few minutes, the round window opening was obliterated with muscle, and the incision was sutured with 4-0 Vicryl Rapide polyglactin in all 3 groups. Distortion-product otoacoustic emissions were obtained before and immediately after the surgical injury, and again on postoperative day 7. Mean signal/noise ratios (S/Ns) obtained at 2, 3, and 4 kHz were calculated, and datasets were compared with nonparametric statistical tests. We found that the early postoperative mean S/N values were significantly lower than the preoperative values in groups 1 and 2, but there was no difference between the mean preoperative values and those obtained on postoperative day 7 in those two groups. In group 3, there were statistically significant differences among the mean preoperative, early postoperative, and postoperative day 7 S/N values. We observed that an electrode insertion into the cochlea via the round window subsequent to mechanical trauma seemed to cause a progressive hearing loss. Therefore, we conclude that special care must be taken to avoid injury to the round window membrane during placement of a cochlear implant electrode, as well as during surgery for chronic otitis media.

Enhanced oval window and blocked round window passages for middle-inner ear transportation of gadolinium in guinea pigs with a perforated round window membrane.

To elucidate the communication between the middle and inner ear, and the fluid dynamics of the inner ear with the perilymphatic fistula (PLF) of the round window membrane (RWM). The PLF of the RWM was created in nine guinea pigs. Gadolinium diethylenetriamine pentaacetic acid bismethylamide (Gd-DTPA-BMA) was delivered into the middle ear and followed in the inner ear using a 4.7 Tesla MRI. Pressure was delivered to the external ear canal of PLF ear in an attempt to enhance the inner ear uptake of Gd-DTPA-BMA. The immediate loading of Gd-DTPA-BMA in the scala tympani of the basal turn was ablated by the outflow of perilymph through the leaking RWM while the oval window passage for Gd-DTPA-BMA was enhanced. There was more Gd-DTPA-BMA distribution in the scala tympani than in the scala vestibuli in the second turn of the PLF cochlea (within 20 min). Signal in the vestibulum and scala vestibuli of the basal turn and rest part of PLF cochlea was greater than that of the control cochlea with intact RWM within 30 min. Pressure applied to the external ear canal tended to enhance the loading of Gd-DTPA-BMA in the perilymphatic scalae of the PLF cochlea. The enhanced oval window passage of Gd-DTPA-BMA was proven by the distorted distribution in the inner ear with PLF. The radial communication of cochlear perilymph was supported by the Gd-DTPA-BMA gradient among the perilymphatic scalae. Applying positive pressure to the external ear canal caused backflow of perilymph into the cochlea which has a potential of transmitting microbes from the middle ear into the inner ear.

Predicting the location of missing outer hair cells using the electrical signal recorded at the round window.

The electrical signal recorded at the round window was used to estimate the location of missing outer hair cells. The cochlear response was recorded to a low frequency tone embedded in high-pass filtered noise conditions. Cochlear damage was created by either overexposure to frequency-specific tones or laser light. In animals with continuous damage along the partition, the amplitude of the cochlear response increased as the high-pass cutoff frequency increased, eventually reaching a plateau. The cochlear distance at the onset of the plateau correlated with the anatomical onset of outer hair cell loss. A mathematical model replicated the physiologic data but was limited to cases with continuous hair cell loss in the middle and basal turns. The neural contribution to the cochlear response was determined by recording the response before and after application of Ouabain. Application of Ouabain eliminated or reduced auditory neural activity from approximately two turns of the cochlea. The amplitude of the cochlear response was reduced for moderate signal levels with a limited effect at higher levels, indicating that the cochlear response was dominated by outer hair cell currents at high signal levels and neural potentials at low to moderate signal levels.

Round window insertion of precurved electrodes is traumatic.

OBJECTIVE: Assess endocochlear trauma by adjusting: 1) location of cochleostomy or round window insertion, and 2) size of precontoured electrode array. STUDY DESIGN: Cadaveric temporal bone study. METHODS: Locations of electrode placement into the cochlea were as follows: 1) round window, 2) anterior inferior to the round window, 3) anterior inferior to the round window niche, 4) superior to the round window niche. Two types of electrode arrays were used: a larger precontoured electrode and thinner precurved research electrode. Histologic sections were made by a blinded third party. RESULTS: Fourteen bones were included in the study. Six (42.8%) of the bones were right ears. Seven bones had no endocochlear trauma. Seven bones have intracochlear trauma. Round window insertions had a high incidence of intracochlear trauma with precontoured electrodes (3/4 bones). Superior cochleostomies with electrode placement had significant intracochlear trauma (2/2 bones). Insertions made anterior inferior to the round window annulus had a 50% incidence of intracochlear trauma (2/4 bones). No endocochlear trauma observed for insertions through traditional cochleostomies (4/4 bones). Less endocochlear trauma was observed with the thinner electrode: 57% versus 42% in the larger electrode array. A higher incidence of tip fold-over was observed with the thinner electrode array (2/7 electrodes). No tip fold-over was noted in the larger electrode. CONCLUSION: The traditional cochleostomy had the least incidence of endocochlear trauma. The smaller electrode array did not significantly affect the incidence of endocochlear trauma, but the thinner array had a higher incidence of tip fold-over, which caused trauma distally. LEVEL OF EVIDENCE: 2C.

Avaliação do trauma intracoclear causado pela inserção do feixe de eletrodos do implante coclear via janela redonda em ossos temporais / Assessment of intracochlear trauma caused by insertion of cochlear implant electrode array via round window in temporal bones

INTRODUÇÃO: A ampliação dos critérios de indicação para cirurgia do implante coclear e os benefícios da preservação da audição residual no pósoperatório estimularam o desenvolvimento de técnicas cirúrgicas atraumáticas. Minimizar os traumas intracocleares durante a inserção do feixe de eletrodos do implante coclear é um passo fundamental para este intuito. O objetivo deste trabalho é avaliar se o trauma intracoclear é diferente quando o feixe de eletrodos do implante coclear é inserido através do quadrante anterossuperior ou anteroinferior da membrana da janela redonda. MÉTODOS: Vinte e cinco ossos temporais frescos de cadáveres humanos foram submetidos à timpanomastoidectomia padrão. Após exposição adequada da membrana da janela redonda, em metade dos ossos o feixe de eletrodos do implante coclear foi inserido via quadrante anterossuperior da membrana da janela redonda, e na outra metade via quadrante anteroinferior. Os ossos temporais foram desidratados e embebidos em epóxi, com o feixe de eletrodos in situ. As peças foram serialmente polidas, tingidas e visualizadas por meio de estereomicroscópio para avaliar o trauma intracoclear causado pela inserção do feixe de eletrodos. As imagens foram fotografadas. RESULTADOS: Em treze ossos temporais o feixe de eletrodos do implante coclear foi inserido via quadrante anterossuperior da membrana da janela redonda, e em doze ossos via quadrante anteroinferior. Obteve-se 372 superfícies. As análises histológicas revelaram diferentes graus de traumas às estruturas intracocleares. Os resultados mostraram que a inserção do feixe de eletrodos via quadrante anterossuperior ou anteroinferior acarretam a mesma frequência de trauma intracoclear. CONCLUSÕES: A presença de trauma intracoclear e a severidade dos traumas ocorridos no tocante à inserção do feixe de eletrodos de implante coclear pelo quadrante anterossuperior e anteroinferior da membrana da janela redonda não apresentou diferença estatisticamente significativa...

INTRODUCTION: The expansion of the indication criteria for cochlear implant surgery and the benefits of preserving residual hearing postoperatively have stimulated the development of atraumatic surgeries. Minimizing the intracochlear traumas during the electrodes insertion is a critical step for this aim. The objective of this study is to assess whether there is a difference in intracochlear trauma when the cochlear implant electrode array is inserted through the anterior-superior or anterior-inferior quadrants of the round window membrane. METHODS: Twenty-five fresh human temporal bones were submitted to standard tympanomastoidectomy. After adequate exposure of the round window membrane, in half of the bones the cochlear implant electrode array was inserted via anterior-superior quadrant of round window membrane and in the other half via anterior-inferior quadrant. The temporal bones were dehydrated and embedded in epoxy with the electrodes array in situ. The specimens were serially polished, stained and viewed through a stereomicroscope to assess the intracochlear trauma caused by insertion of the electrode array. Resulting images were documented. RESULTS: In thirteen temporal bones the cochlear implant electrode array was inserted via anterior-superior quadrant of round window membrane and in twelve bones via anterior-inferior quadrant. Three hundred and seventy two surfaces were obtained. Histological examinations revealed varying degrees of damage to the intracohlear structures. The results showed that the insertion of the electrode array via anterior-superior or anterior-inferior quadrant lead to the same frequency of intracochlear trauma. CONCLUSIONS: The presence of intracochlear trauma and severity of traumas regarding the insertion of cochlear implant electrode array via anterior-superior and via anterior-inferior quadrant of the round window membrane showed no statistically significant difference. However, it was observed that surgical exposure...

Round window versus cochleostomy technique in cochlear implantation: histologic findings.

HYPOTHESIS: Cochleostomy or round window enlargement techniques for cochlear implant electrode insertion result in more abnormal tissue formation in the basal cochlea and are more apt to produce endolymphatic hydrops than round window electrode insertion. METHODS: Twelve temporal bones from implanted patients were examined under light microscopy and reconstructed with 3-dimensional reconstruction software to determine cochlear damage and volume of neo-ossification and fibrosis after electrode insertion. Amount of new tissue was compared between 3 groups of bones: insertion through the round window (RW), after enlarging the RW (RWE) and cochleostomy (Cochl). The probable role of the electrode was evaluated in each case with hydrops. RESULTS: More initial damage occurred in the Cochl and RWE groups than in the RW group, and the difference was significant between RWE and RW in cochlear segment I (p < 0.026). The volume of new bone in Segment I differed significantly between groups (p < 0.012) and was greater in the RWE group than in either the Cochl or RW groups (post hoc p's < 0.035 and 0.019, respectively). Hydrops was seen in 5 cases, all in the Cochl and RWE groups. Blockage of the duct was because of new tissue formation in 4 of the 5 hydrops cases. CONCLUSION: With the electrodes in this series, implantation through the RW minimized initial intracochlear trauma and subsequent new tissue formation, whereas the RW extension technique used at the time of these implantations produced the greatest damage. Future studies may clarify whether today's techniques and electrodes will produce these same patterns of damage.

Cochlear implant insertion forces in microdissected human cochlea to evaluate a prototype array.

Cochlear implant array insertion forces are potentially related to cochlear trauma. We compared these forces between a standard (Digisonic SP; Neurelec, Vallauris, France) and an array prototype (Neurelec) with a smaller diameter. The arrays were inserted by a mechatronic tool in 23 dissected human cochlea specimens exposing the basilar membrane. The array progression under the basilar membrane was filmed together with dynamic force measurements. Insertion force profiles and depth of insertion were compared. The recordings showed lower insertion forces beyond 270° of insertion and deeper insertions with the thin prototype array. This will potentially allow larger cochlear coverage with less trauma.

Development and evaluation of the modiolar research array--multi-centre collaborative study in human temporal bones.

OBJECTIVE: Multi-centre collaborative study to develop and refine the design of a prototype thin perimodiolar cochlear implant electrode array and to assess feasibility for use in human subjects. STUDY DESIGN: Multi-centre temporal bone insertion studies. MATERIALS AND METHODS: The modiolar research array (MRA) is a thin pre-curved electrode that is held straight for initial insertion with an external sheath rather than an internal stylet. Between November 2006 and February 2009, six iterations of electrode design were studied in 21 separate insertion studies in which 140 electrode insertions were performed in 85 human temporal bones by 12 surgeons. These studies aimed at addressing four fundamental questions related to the electrode concept, being: (1) Could a sheath result in additional intra-cochlear trauma? (2) Could a sheath accommodate variations in cochlea size and anatomies? (3) Could a sheath be inserted via the round window? and (4) Could a sheath be safely removed once the electrode had been inserted? These questions were investigated within these studies using a number of evaluation techniques, including X-ray and microfluoroscopy, acrylic fixation and temporal bone histologic sectioning, temporal bone microdissection of cochlear structures with electrode visualization, rotational tomography, and insertion force analysis. RESULTS: Frequent examples of electrode rotation and tip fold-over were demonstrated with the initial designs. This was typically caused by excessive curvature of the electrode tip, and also difficulty in handling of the electrode and sheath. The degree of tip curvature was progressively relaxed in subsequent versions with a corresponding reduction in the frequency of tip fold-over. Modifications to the sheath facilitated electrode insertion and sheath removal. Insertion studies with the final MRA design demonstrated minimal trauma, excellent perimodiolar placement, and very small electrode dimensions within scala tympani. Force measurements in temporal bones demonstrated negligible force on cochlear structures with angular insertion depths of between 390 and 450°. CONCLUSION: The MRA is a novel, very thin perimodiolar prototype electrode array that has been developed using a systematic collaborative approach. The different evaluation techniques employed by the investigators contributed to the early identification of issues and generation of solutions. Regarding the four fundamental questions related to the electrode concept, the studies demonstrated that (1) the sheath did not result in additional intra-cochlear trauma; (2) the sheath could accommodate variations in cochlea size and anatomies; (3) the sheath was more successfully inserted via a cochleostomy than via the round window; and (4) the sheath could be safely removed once the electrode had been inserted.

Perilymphatic fistula in guinea pigs: natural evolution versus surgical treatment.

UNLABELLED: Perilymphatic fistulas still represent a major treatment challenge. In some cases, its surgical closure can reduce auditory and vestibular sequelae. AIM: To compare the behavior of cochlear window perilymphatic fistulas in guinea pigs as to their natural evolution and immediate surgical closure. MATERIALS AND METHODS: Experimental study. Forty guinea pigs were submitted to cochlear window membrane lesion and randomly broken down into two groups: open fistula (OF) and surgically closed fistula (SCF). We found the summation potential (SP) and action potential (AP) latencies and amplitudes and the SP/AP ratio at three times: pre-fistula (PRE), immediate post-fistula (IPF) and late post-fistula (LPF). RESULTS: There was a significant drop in amplitudes and raise in SP and AP latencies among the times studied. As to the SP/AP ratios, there was a reduction between PRE and IPF, both were significant. There was no behavior difference between the OF and SCF. CONCLUSIONS: Within the time frame considered, guinea pigs submitted to cochlear window membrane lesions evolved with a worsening in potentials and latencies. Despite the partial improvement in electrophysiological parameters, surgical closure did not prove statistically more effective than natural evolution.

Fístula perilinfática em cobaias: comparação entre evolução natural e correção cirúrgica / Perilymphatic fistula in guinea pigs: natural evolution versus surgical treatment

As fístulas perilinfáticas ainda constituem um grande desafio quanto ao seu tratamento. Em alguns casos, seu fechamento cirúrgico pode reduzir as sequelas auditivas e vestibulares. OBJETIVO: Comparar o comportamento de fístulas perilinfáticas de janela coclear em cobaias quanto à evolução natural e fechamento cirúrgico imediato. MATERIAL E MÉTODOS: Estudo experimental. Quarenta cobaias foram submetidas à lesão da membrana da janela coclear e divididas em dois grupos aleatoriamente: fístula aberta (FA) e fístula fechada cirurgicamente (FF). Foram determinadas as amplitudes e latências do potencial de somação (PS) e do potencial de ação (PA) e da relação PS/PA em três momentos: pré-fístula (PRÉ), pós-fístula imediato (PFI) e pós-fístula tardio (PFT). RESULTADOS: Observou-se significativa queda das amplitudes e aumento das latências do PS e PA entre os momentos considerados. Quanto à relação PS/PA, houve diminuição entre PRÉ e PFI mas aumento entre PFI e PFT, ambos significantes. Não houve diferença de comportamento entre os grupos FA e FF. CONCLUSÕES: No período considerado, cobaias submetidas a lesões da membrana da janela coclear evoluíram com piora dos potenciais e latências. Apesar da melhora parcial dos parâmetros eletrofisiológicos o fechamento cirúrgico não se mostrou estatisticamente mais efetivo que a evolução natural das mesmas.

Perilymphatic fistulas still represent a major treatment challenge. In some cases, its surgical closure can reduce auditory and vestibular sequelae. AIM: to compare the behavior of cochlear window perilymphatic fistulas in guinea pigs as to their natural evolution and immediate surgical closure. MATERIALS AND METHODS: Experimental study. Forty guinea pigs were submitted to cochlear window membrane lesion and randomly broken down into two groups: open fistula (OF) and surgically closed fistula (SCF). We found the summation potential (SP) and action potential (AP) latencies and amplitudes and the SP/AP ratio at three times: pre-fistula (PRE), immediate post-fistula (IPF) and late post-fistula (LPF). RESULTS: There was a significant drop in amplitudes and raise in SP and AP latencies among the times studied. As to the SP/AP ratios, there was a reduction between PRE and IPF, both were significant. There was no behavior difference between the OF and SCF. CONCLUSIONS: Within the time frame considered, guinea pigs submitted to cochlear window membrane lesions evolved with a worsening in potentials and latencies. Despite the partial improvement in electrophysiological parameters, surgical closure did not prove statistically more effective than natural evolution.

Factors influencing the efficacy of round window dexamethasone protection of residual hearing post-cochlear implant surgery.

AIM: To protect hearing in an experimental model of cochlear implantation by the application of dexamethasone to the round window prior to surgery. The present study examined the dosage and timing relationships required to optimise the hearing protection. METHODS: Dexamethasone or saline (control) was absorbed into a pledget of the carboxymethylcellulose and hyaluronic acid and applied to the round window of the guinea pig prior to cochlear implantation. The treatment groups were 2% w/v dexamethasone for 30, 60 and 120min; 20% dexamethasone applied for 30min. Auditory sensitivity was determined pre-operatively, and at 1 week after surgery, with pure-tone auditory brainstem response audiometry (2-32kHz). Cochlear implantation was performed via a cochleostomy drilled into the basal turn of the cochlea, into which a miniature cochlear implant dummy electrode was inserted using soft-surgery techniques. RESULTS: ABR thresholds were elevated after cochlear implantation, maximally at 32kHz and to a lesser extent at lower frequencies. Thresholds were less elevated after dexamethasone treatment, and the hearing protection improved when 2% dexamethasone was applied to the round window for longer periods of time prior to implantation. The time that dexamethasone need be applied to achieve hearing protection could be reduced by increasing the concentration of steroid, with a 20% application for 30min achieving similar levels of protection to a 60min application of 2% dexamethasone. CONCLUSIONS: Hearing protection is improved by increasing the time that dexamethasone is applied to the round window prior to cochlear implantation, and the waiting time can be reduced by increasing the steroid concentration. These results suggest that the diffusion dexamethasone through the cochlea is the prime determinant of the extent of hearing protection.

Analysis of 60 patients after tympanotomy and sealing of the round window membrane after acute unilateral sensorineural hearing loss.

OBJECTIVE: This retrospective study was performed to evaluate the effectiveness of tympanotomy and sealing of the round window membrane after unilateral acute hearing loss. DESIGN: All patients presenting idiopathic sudden hearing loss, acoustic, or barotrauma were treated with prednisolone and caroverine. Thirty-six patients had a mean pure tone hearing level worse than 70 dB. Recovery was defined as improvement of hearing threshold for 5 frequencies (250, 500, 1000, 2000, and 4000 Hz). If hearing did not improve after conservative treatment, an exploratory tympanotomy and sealing of the round window membrane were suggested. In the last 8 years, 60 patients with idiopathic sudden hearing loss, acoustic, or barotrauma underwent tympanotomy. RESULTS: In 40 patients, we observed improvement of hearing level up to complete remission. In 20 patients, no change could be detected. In the group of patients with documented barotrauma, 12 patients showed improved hearing levels. Of 37 patients with idiopathic sudden hearing loss, 26 had an improved hearing after surgery. Most patients were operated on within 14 days (range, 1-60 days), but time of surgery had no influence on outcome in patients with idiopathic hearing loss. In contrast, in patients with barotrauma, time of surgery seems to have an influence on outcome. CONCLUSIONS: Tympanotomy and sealing of the round window membrane can be recommended in cases of acute hearing loss after failure of conservative treatment.

[The risk of damaging the round window by CO2 laser myringotomy. A morphological experimental analysis of 61 human petrous bone specimens]. / Die Gefährdung des runden Fensters bei der CO2-Laser-Parazentese. Eine morphologisch-experimentelle Analyse an 61 humanen Felsenbeinen.

INTRODUCTION: In CO2 laser myringotomy, a self-healing perforation is typically created in the lower anterior quadrant. A prominent anterior meatal wall may cover that quadrant and necessitate dorsal perforation of the eardrum. This study orientationally assessed the risk of damaging the round window membrane (RWM) when applying the laser in dorsal eardrum areas. MATERIALS AND METHODS: The round window was exposed by otomicrosurgery in 61 human petrous bone specimens. CO2 laser myringotomy was previously performed with twice the standard power (25 W, 180 ms, 2.2 mm) in the lower posterior quadrants of 25 specimens, the beam being applied directly to the round window niche in five specimens, and the effect of the laser radiation was documented. The RWM was subsequently exposed in all petrous bones, and the angle correlation of the membrane to the direction of the laser beam was digitally measured. RESULTS: The laser did not damage the membrane of the round window in any of the cases. The angle between the RWM and the external auditory meatus was below 30 degrees in 97% of the petrous bones and thus had a nearly parallel course. CONCLUSION: Localization of the window caudodorsal to the meatal wall, bone overhanging the membrane, mucosal duplications, and membrane alignment nearly parallel to the laser beam make it virtually impossible to reach this membranous structure with the CO2 laser.