Wall Of External Auditory Canal Research Articles

Malignant myoepithelioma of the external auditory canal — a rare case report with literature review and clinical importance of foramen of Huschke

BackgroundA malignant myoepithelioma is a rare tumor, mostly arising from the salivary glands. Myoepitheliomas of the ear have rarely been reported. The manuscript reports myoepithelial carcinoma of the external auditory canal (EAC) spreading to the infratemporal fossa. A clinician must be aware of anatomical variation of the bony EAC wall, such as the foramen of Huschke. This rare defect may be a pathway for spreading pathologies between these two anatomical regions.Case reportWe present a case of osteoma-like stenosis of the EAC, which turned out to be an extremely rare malignant tumor. The preoperative MRI and PET/CT revealed that two parts of the tumor communicated through a defect in the antero-inferior portion of the bony ear canal. No distant metastases were detected. Subsequently, the tumor was resected from the ear canal and the infratemporal fossa en bloc. Perioperatively the defect in the EAC wall was suspected of the foramen of Huschke. After the surgery, the older scans of the patient from the past showed no presence of a congenital EAC wall defect. Therefore, the authors concluded that the tumor aggressively grew through the bone due to its biological nature.ConclusionMalignant myoepithelioma of the external auditory canal is an extremely rare condition and could be misdiagnosed as other benign lesions. In cases of suspicious lesions, it is advisable to do a probatory biopsy from the EAC. Surgery is the treatment of choice in malignant myoepitheliomas, and regular follow-ups are essential to monitor for recurrence or metastatic disease. Any mass located at the antero-inferior portion of the EAC wall warrants close evaluation due to its potential for expansion from the EAC.

Comparison of Preoperative Computerized Tomograghic Scan of Temporal Bone Findings with Intra Operative Findings in Patients with Chronic Otitis Media Undergoing Tympanomastoidectomy: A Descriptive Study

Background: Since ancient times, chronic suppurative otitis media (CSOM) has been a significant contributor to middle ear illness. Antibiotics have been extremely helpful, but (CSOM) is still a frequent condition, and its consequences present a challenge to both otologists and radiologists. Due to the intricate anatomical nature of the middle ear and inner ear, radiological assessment of the temporal bone is challenging.
 Aim of the Study: To compare between preoperative CT scan findings of the temporal bone with the operative findings in patients with CSOM undergoing tympanomastoidectomy.
 Methodology: A Descriptive cross-sectional prospective has been adopted and 35 patients with Chronic Suppurative Otitis Media were admitted at the Department of Otolaryngology/ Alsulaymaniyah Teaching Hospital of Otolaryngology, Head and Neck Surgery, and Zhian Hospital during the period from February to December 2015. A detailed history and careful physical examination, clinical tests revealed that all of the patients had Chronic Suppurative Otitis Media, typically with discharge from the ear and hearing loss. Each patient had their clinical history collected, and they all underwent a thorough ear, nose, and throat examination as well as an attentive otoscopic and microscopic ear examination. Additionally, all patients underwent an audiological evaluation that included pure tone audiometry, tympanometry, and HRCT.
 Results: Thirty -five patients were included in this study. The mean age of the patients was 33 years; 51.4% were males and 48.6% were females. The most common presenting symptom was aural discharge in 71.4%; the second one was hearing loss in 28.6%. Mastoid pneumatization was found in 82.9% by CT while by surgery, it was found in 17.1%. CT findings showed that middle ear involvement in 11.4%, mastoid involvement in 11.4%, mastoid with middle ear involvement in 54.3%, and EAC, mastoid, and middle ear involvement in 17.1%. While the surgical findings showed middle ear disease in 20%, mastoid involvement in 11.4%, mastoid with middle ear involvement in 57.1%, and EAC, mastoid and middle ear involvement in 11.4%. The CT findings for eroded Malleus, Incus integrity, and stapes in 31.4%, 37.1%, not visualized while surgical findings showed eroded Malleus, Incus, and stapes integrity that 28.6%, 54.3%, and 28.6% respectively. The CT findings for an eroded facial canal, the lateral semicircular canal, the posterior external auditory canal wall, and sigmoid sinus plate integrity were 12.4%, 8.6%, 22.9%, and 11.4% in that order, while the surgical findings of the eroded facial canal, the lateral semicircular canal, and the posterior external auditory canal wall were found in 20.0%, 5.7%, 17.1%, and 14.2% respectively. Both CT and surgical findings of Integrity of the tegmen showed that 32 patients (91.4%) were found to have intact tegmen, and 3 patients (8.6%) had eroded tegmen and both showed that the eroded scutum found in 25.7%.
 Conclusions: The current study concluded a positive correlation between CT and surgical findings that has many advantages in preoperative planning for the eradication of the disease, choosing the best approach & has a very important role in the orientation of the surgeon during the surgery to avoid any possible complications.

Temporomandibular joint herniation into the external auditory canal presenting as clicking tinnitus: A case report

ABSTRACT Background Herniation of the temporomandibular joint (TMJ) into the external auditory canal (EAC) due to a bony defect in the EAC is rare. Such bony defects can be secondary to inflammation, neoplasm, trauma. In rare instances, TMJ herniation can occur when the Huschke foramen is constantly exposed. TMJ herniation can induce clicking tinnitus, otalgia, conductive hearing loss, and otorrhea, but can also present with no symptoms. This study reports a case of TMJ herniation. Clinical presentation A male patient presented with clicking tinnitus that had developed 3 years ago. Dome-shaped soft tissue was found on the anterior EAC wall, which protruded and depressed with mouth movement. The patient underwent surgical reconstruction of the bony defect with titanium mesh, and the symptoms resolved after surgery. Conclusion This case highlights the importance of surgical reconstruction of a bony defect in the EAC using appropriate materials.

An endoscopic approach to stapes surgery needs less external auditory canal wall removal than a microscopic approach

Background Although many advantages of endoscopic stapes surgery have been reported, there is little objective data on whether it provides better visualization than the microscopic approach. Objectives To evaluate and compare audiological results, external auditory canal wall removal area, and adverse event rates between endoscopic and microscopic stapes surgery. Material and methods Data from patients who received stapedotomy were collected. Pre and postoperative audiometry, procedure-related parameters, and adverse events were analyzed in conventional microscopic and endoscopic groups. Results There were no differences in procedure time or postoperative hearing between the endoscopic and microscopic surgery groups. The mean procedure times were 87.3 ± 18.9 min in the endoscopic group and 79.9 ± 23.5 min in the microscopic group. The mean postoperative air-bone gaps were 10.9 ± 8.3 dB in the endoscopic group and 10.5 ± 7.8 dB in the microscopic group. There were no differences in the rate of sensorineural hearing loss, postoperative pain, facial palsy, vertigo, or dysgeusia between the two groups. The bony removal area of the posterosuperior external auditory canal wall measured by two observers was significantly less in the endoscopic group than in the microscopic group. Conclusions Endoscopic stapedotomy needed less external auditory canal wall removal and showed similar audiological outcomes to microscopic stapedotomy.

Management of External Auditory Canal Anterior Wall Defect: A Case Series and Literature Review.

Although rare in etiology, anterior bony wall defects of the external auditory canal (EAC) accompanied by temporomandibular joint herniation may cause various otologic symptoms. Surgical treatment can be considered based on symptom severity because many previous case reports have highlighted its efficacy. This study aimed to review the long-term results of surgical treatment of EAC anterior wall defect and to suggest a stepwise approach when creating a treatment plan. We performed a retrospective review of 10 patients who underwent surgical management to address the EAC anterior wall defect and its associated symptoms. Medical records, temporal bone computed tomography scans, audiometry, and endoscopic examination findings were analyzed. The primary repair of the EAC defect was the first to be surgically addressed in most cases, excluding one case with a severe combined infection. Of the 10 cases, 3 patients exhibited either postoperative complications or symptom recurrence. Six patients had resolved symptoms consequent to primary surgical repair, and four patients underwent revision surgery undergoing a more invasive procedure, such as canalplasty or mastoidectomy. Primary repair of the anterior wall defect of the EAC seems to be overpromoted for lasting results but is not as promising as previously noted. We therefore propose to create a novel treatment flowchart regarding the surgical treatment of anterior wall defects of the EAC based on clinical experience. IV.

A Case of Reconstruction of Large Defect in Posterior Wall of Bony External Auditory Canal Using Cavum Conchal Cartilage

External auditory canal (EAC) wall defect may occur due to cholesteatoma, and surgeries for chronic ear diseases, trauma, neoplasm or idiopathic. Conservative treatment is available if the severity of the symptom is mild or asymptomatic. However, these defects require repairment not only to attain relief from intermittent otologic symptoms but also to prevent retraction pockets and sequential cholesteatoma. There have been no reported cases of reconstruction of EAC wall defect by cartilage with perichondrium and groove of wall defect by drilling. We manipulated the conchal cartilage so that it could effectively provide robust reconstruction of the canal wall defect. Herein we report a case of EAC reconstruction with mastoidectomy with no further complications.

CT findings in temporal bone sites in skull base osteomyelitis from malignant otitis externa.

To identify the earliest sites and spread patterns of bony erosions on high-resolution temporal bone computerized tomographic (HRTBCT) scans and conjugate the radiological findings with clinical/laboratory data for guiding the interpretation of CT images of skull base osteomyelitis (SBOM) from malignant otitis externa (MOE). Retrospective and prospective medical records analysis. The medical records of all patients who presented to a referral medical center during 2015-2022 and initially diagnosed with SBOM. Radiological assessment of each sub-site was performed by 2 qualified neuro-radiologist, who were blind to the clinical data. 33 patients were enrolled. All patients suffered edema and exudates of the external auditory canal (EAC). The most common osseous markers for SBOM were dehiscence or irregularity of the anterior EAC wall and temporomandibular joint (TMJ) medial wall (21/33, 64% patients, each), followed by a fistula from the TMJ to the EAC (20/33, 61% patients). Eustachian tube bony walls and condylar irregularity and/or dehiscence were as prevalent as 16/33, 48% of patients, each. EAC inferior and posterior walls of the EACs were irregular or dehiscent in patients with more advanced disease. The high symptomatologic overlap between SBOM and other aural pathologies might cause diagnostic (and subsequent treatment) delay and result in dire complications. EAC edema and irregularity or dehiscence of the anterior EAC wall are the most common early CT findings associated with SBOM caused by MOE.

Study on CT features of congenital branchial cleft anomaly in children

Objective:To summarize the CT features of congenital branchial cleft anomaly in children, to reduce misdiagnosis and improve surgical strategy. Methods:This study enrolled 323 pediatric patients with congenital first branchial cleft anomaly, congenital second branchial cleft anomaly and congenital piriform sinus fistula confirmed by surgery and post-operative histopathology, who was admitted to Shanghai Children's hospital from August 2014 to January 2021., CT imaging data were retrospectively analyzed. Results:A total of 323 children with congenital branchial cleft deformity were included. There were 145 males and 178 females, aged from 22 days to 15 years. 119（119/323, 36.8%） cases were diagnosed as congenital first branchial cleft anomaly. Among them, 96 cases（96/119, 80.67%） were related to the wall of external auditory canal, and 89 cases（89/119, 74.78%） were related to parotid gland. The positive rate of CT examination was 87.4%（104/119）. 57 cases（57 / 323, 17.6%） had congenital second branchial cleft anomaly. Among them, 46 cases（46/57, 80.7%） were related to submandibular gland. The positive rate of CT examination was 84.2%（48/57）. 147 cases（147/323, 45.5%） had congenital piriform sinus fistula, in which 129 cases（129/147, 87.8%） were related to thyroid. The positive rate of CT was 89.1%（131/147）. Conclusion:The CT findings of congenital first branchial cleft anomaly are characterized by lesions in the inferior and/or posterior wall of ipsilateral external auditory canal and parotid gland. The CT features of congenital second branchial cleft anomaly are that the lesion is located on the ipsilateral submandibular gland （posterior and medial）. The CT features of congenital piriform sinus fistula are that the focus is located on the dorsal side of the upper pole of the lateral lobe of the thyroid gland.

Abnormal bone loss in the external auditory canal of two adult humans from the medieval period of Germany—An attempt at differential diagnosis

AbstractAbnormal loss of bone in the external auditory canal (EAC) constitutes an underreported condition in paleopathology. Thus far, all reported cases were diagnosed as the result of an external ear canal cholesteatoma (EACC). Here, we report two cases from the medieval period in Germany that show enlarged EACs with perforations of the anterior and posterior EAC walls. The cases were studied macroscopically, with a digital stereo microscope and by conventional X‐ray and computed tomography (CT)‐imaging techniques. In Case 1, the resorption caused a “ballooning” of the EAC while signs of osteonecrosis were missing. We therefore conclude that keratosis obturans (KO) is the most likely diagnosis. In Case 2, the periantral region adjacent to the perforations of the posterior EAC wall exhibits large resorption cavities and sequestrum‐like structures, indicative of osteonecrosis. In this case, we arrive at the diagnosis EACC. Ear diseases encompass a broad spectrum of conditions, many of them with potentially severe impacts on past people. It is therefore suggested to address ear diseases more frequently in paleopathology. Thus far, only a very limited number of entities of ear diseases have been diagnosed in paleopathological studies, and no case of KO has been reported. The present study thus expands the spectrum of paleo‐otopathological diagnoses.

Soft tissue lesion of the ear canal – Now you see it, now you don’t

Spontaneous herniation of the temporomandibular joint along a bony defect in the external auditory canal is an uncommon condition that may lead to otologic symptoms. A 43-year-old gentleman presented with otalgia and an external auditory canal soft tissue lesion, which flattens upon opening of the jaw. Computed tomography scan of the temporal region confirmed the presence of a soft tissue lesion that herniated through an external auditory canal wall defect. This condition should be included in the differential diagnoses of an external auditory canal mass, despite infrequently encountered. It is important to inspect the external auditory canal during movement of the jaw when a soft tissue lesion is noted, so as not to miss this diagnosis.

Protrusion of Implant after Surgical Wall Reconstruction due to Temporomandibular Joint Herniation

Herniation of the temporomandibular joint (TMJ) into the external auditory canal is rare as TMJ and external auditory canal are separated by an anterior bony wall of external auditory canal. The bony defect of the anterior external auditory canal can be caused by trauma, otologic procedure, neoplasm, inflammation and a rare congenital bony defect. Conservative treatment is available if the severity of the symptom is mild or asymptomatic. However, surgical procedure is considered if the patient experiences severe distress. There have been no reported cases of surgical-related complications and recurrence during postoperative follow-up period. Herein we report the very first case of foreign body prolapse involving herniation from TMJ extending into the external auditory canal.

FORAMEN TYMPANICUM- AN EMBRYOLOGICAL DEFECT IN TYMPANIC PLATE

Foramen tympanicum or Foramen Huschke is a bony defect in the tympanic part of temporal bone that persists after 5 years of age. Due to this, there is a chance of discharge in the ear leading to perisistent otitis externa , herniation of soft tissue into auditory canal and due to the communication there is higher chances of parotid infections to be transmitted into the EAC . The present study was conducted on 40 dried human crania .The tympanic part of temporal bone that forms the inferior wall of external auditory canal was studied to find any developmental defect - foramen tympanicum . Out of all crania studied , foramen tympanicum was observed on right side in two crania and on both sides in one cranium .The persistant foramen can produce clinical complications like fistula formation or herniation of tissues into external auditary canal.. Knowledge of this embryological defect is useful for ENT and Maxillofacial surgeons to avoid complications during operative procedures of this region and also to diagnose rare clinical presentations like persistent or chronic pain in the region of Temporomandibular joint.

Zygomatic root abscess: A rare entity not to be forgotten!

Zygomatic root abscess is a rare extracranial extratemporal complication of otitis media. To the best of our knowledge, there are only a few scattered cases of zygomatic root abscesses reported in the literature. We present an unusual case of a zygomatic root abscess in a 24 years old adult. He presented with one month duration of right zygomatic swelling. Otoscopic examination revealed superior and posterior external auditory canal wall sagging with an intact tympanic membrane. High Resolution Computed Tomography (HRCT) temporal bone revealed a rim enhancing lesion lateral to the zygomatic process with fluid filled mastoid air cells. He was managed with antibiotics and staged surgical interventions. He recovered well. Our case serves to shed light on the pathways of infection, clinical manifestations and timely staged surgical intervention in this rare pathology.

외이도 재건을 위해 잔존 외이도 후벽을 보존한 채 시행한 개방형 유양동 삭개술 4예

The aim of cholesteatoma surgery is to completely eradicate cholesteatoma and to reconstruct the normal anatomy of the middle ear. Canal wall down mastoidectomy (CWD) is often applied for the complete eradication of cholesteatoma and prevention of recurrence in patients with cholesteatoma. However, CWD involves a significant destruction of the middle ear and the mastoid anatomy, that leads to potential complications including chronically draining cavity, retention of debris that requires frequent cleaning, and difficulty in fitting a hearing aid. To resolve these problems, surgeons have attempted to reconstruct posterior external auditory canal wall with a variety of techniques and materials. We recently experienced four cases of patients who had tympanomastoid surgery because of cholesteatoma. In the operation, superior segment of posterior canal wall was removed but remnant inferior segment of posterior canal wall was preserved. CWD with preservation of the remnant canal wall was performed unlike the conventional CWD operation. Surgical view was sufficient to eradicate the entire cholesteatoma. Canal wall reconstruction was done with remnant canal wall and conchal cartilage, and then mastoid obliteration was done with Tissue glue mixed demineralized bone matrix. This procedure was enough to eradicate cholesteatoma without lowering facial ridge. Saucerization, mastoid tip amputation and meatoplasty were not even needed. We report these four cases with a review of literature. (J Clinical Otolaryngol 2020;31:63-69)

Otoscopy and imaging features of spontaneous temporomandibular joint herniation into the external auditory canal.

Objective:To explore the otoscopy, CT and MRI features of spontaneous temporomandibular joint(TMJ）herniation(STMJH) into the external auditory canal (EAC) through the persistent foramen of Huschke (PFH).Methods:15 cases diagnosed STMJH were collected. The otoscopy, CT data of 15 cases and MRI data of 6 cases were retrospectively reviewed.Results:Otoscopy revealed a mass located in the anterior wall of the bony EAC that moved forwards and backwards during mouth opening and closing, respectively. CT showed a soft mass with bony defect in the anterior wall of the EAC, with no enhancement; the bony defect margin was well defined in all cases. The bone adjacent to the PFH was pressed and partially wrapped around the soft mass, as if “holding a ball,” in seven cases. Pseudobone shell around the soft mass was observed in eight cases. Six cases included MRI scans, which showed TMJ soft tissue herniated into the EAC.Conclusion:STMJHs have unique otoscopic, CT and MRI features. The examination strategy recommended is dynamic otoscopy and conventional CT, MRI can be chosen when the herniation is complicated by infection or otitis externa or when the patient has TMJ dysfunction; conservative management and follow-up observations are the main treatment strategy recommended.Advances in knowledge:Mechanical stress of TMJ on the EAC is thought to cause herniation and the special CT features, the location and size of the PFH, especially the location, are the major risk factors for TMJ herniation in patients with FH.

On the Representative CT Image of an Otic-Disrupting Fracture

Dear Editor:
 In the article entitled “Facial Paralysis in Longitudinal versus Oblique and Otic-Sparing versus Non Otic-Sparing Temporal Bone Fracture” published in the Vol 34 No 2 issue of the Philippine Journal of Otolaryngology Head and Neck Surgery, the authors included an image (Figure 4) that was representative of an otic-disrupting fracture. The arrow clearly shows the fracture line running through the mastoid air cell system nearly parallel to the posterior external auditory canal wall and ending just posterior to the ossicular chain.
 However, the fracture line does not unequivocally appear to proceed medially towards the otic capsule, which is the densest portion of the temporal bone that surrounds the osseous labyrinth, and includes the cochlea, vestibule and semicircular canals. The otic capsule likewise is located within the petrous portion of the temporal bone.1 The otic capsule lies within the oval ring in the smaller figure above which is an enlarged image of the original figure in the article.
 This issue is relevant because the authors are classifying subjects according to the visual presence of a fracture that may or may not involve the otic capsule. Misidentification of the type of fracture in a representative image raises the question of a systematic misidentification in the entire data set, thus rendering the results of the study invalid.

A Case of Bony Defect of the Anterior External Auditory Canal Wall Causing Ear Fullness

A congenital defect of the anterior wall of the external auditory canal (EAC) is known as foramen of Huschke. The tympanic bone is incompletely developed and has a U shape at birth. The foramen of Huschke closes via continuous bone growth, which occurs before the age of 5 years. A persistent foramen of Huschke is an anatomic variation located in the anteroinferior portion of EAC, which can cause ear discomfort with spontaneous temporomandibular joint (TMJ) herniation into the EAC bony defect. We present a case of 50-year-old man who had a symptomatic TMJ herniation through an osseous defect. The physical examination showed a bulging mass of anterioinferior portion of EAC when the patient closed his mouth, which was retracted when the mouth openned. We report a case of surgical reconstruction of the EAC wall defect, and the foramen of Huschke with titanium mesh via preauricular approach along with literature’s review.

Cautionary High-resolution Computed Tomography Findings for the Presence of Facial Canal Dehiscence in Patients with Cholesteatoma.

ObjectiveThis study aimed to investigate the abnormal high-resolution computed tomography (HRCT) findings in cholesteatomatous chronic otitis media (CCOM) patients preoperatively and the coexistence of abnormal HRCT findings with facial canal dehiscence (FCD) observed intraoperatively to identify the predictive factors associated with FCD.MethodsThe medical records of 151 CCOM patients who had undergone tympanomastoidectomy at our center were retrospectively examined in terms of the patients’ age and gender, preoperative HRCT findings [scutum defect, posterior wall of external auditory canal (PWEAC) defect, lateral semicircular canal (LSSC) defect, tegmen defect, and sigmoid plate erosion]. Operation records containing information about FCD were also analyzed.ResultsThe prevalence of FCD was found to be 33.8% (51/151). There was a significant correlation between the presence of scutum, PWEAC, LSSC, and tegmen defects and the presence of FCD. However, no statistically significant correlation was found between the presence of sigmoid plate erosion and the presence of FCD. The results of regression analysis of the coexisting pathologic findings for FCD showed that the risk of FCD was highest in patients with LSSC + scutum defects (34.3-fold increase), followed by LSSC + PWEAC defects (31.6-fold increase).ConclusionOur study revealed that the presence of scutum, PWEAC, LSSC, and tegmen defects on HRCT indicates a higher risk of FCD preoperatively. This risk is even greater when multiple abnormal findings coexist.

A Curious Case of Crystal Deposit Disease in the Petrous Bone

Crystal deposit disease is a rare disorder with benign dense soft tissue calcium containing accumulations presenting as pseudogout or tumoral calcinosis. It rarely affects the head and neck region and even less to the petrous bone. We describe a case of para-articular tumoral calcinosis involving the external auditory canal wall in close proximity to the temporomandibular joint with extension towards the middle cranial fossa floor in a 73-year-old man presenting with otalgia and progressing mixed hearing loss. Subtotal petrosectomy with obliteration of the middle ear and mastoid was done with complete removal of the lesion. We discuss the course, treatment and final pathology with possible explanations for the pathophysiology in this particular case. Although tumoral calcinosis is uncommon, this entity should be considered in the differential diagnosis when an osteogenic temporal lesion is seen on computed tomography or magnetic resonance imaging. The treatment for this benign tumor includes complete excision of the lesion in symptomatic cases. Proper evaluation including anamnesis of the family history and previous trauma as well as serology should be done. The exact etiology and classification of crystal deposit diseases require further study.

Cochlear Implant Surgery Through Round Window Approach Is Always Possible.

The benefit of round window (RW) approach for cochlear implant (CI) has been well studied. Because the RW represents a natural door to scala tympani, it facilitates precise electrode insertion. Atraumatic electrode insertion can also be performed without drilling the cochlear lateral wall. However, the RW approach has several limitations. The purpose of this study is to describe successful CI surgeries utilizing the RW approach except for severe cases of temporal bone anomaly. The authors' successful surgical solution for cases involving difficult RW access is also described. We retrospectively analyzed 377 consecutive surgeries of cochlear implantation performed between June 2010 and December 2018 by a single experienced surgeon. Standard and alternative procedures were used according to anatomical variations. Standard procedures included modified techniques of mastoidectomy in the RW approach, opening of facial recess, exposure of RW membrane, and electrode insertion. Difficult cases involving severe rotated cochlea or hypoplastic mastoid were successfully treated with RW insertion using alternative procedures such as external auditory canal (EAC) wall mobilization and endomeatal approach. We performed CI surgery through a reproducible RW technique in two cases involving endomeatal approach and three cases of EAC mobilization. Other cases were treated using the standard procedure. Cochlear implant surgery through RW is reliable, safe, and effective. The RW technique is reproducible via several surgical procedures in most CI cases. Identification and safe exposure of RW membrane is a prerequisite for successful electrode insertion in cochlear implant surgery.