Translabyrinthine Approach Research Articles

Ipsilateral Cochlear Implantation After Cochlear Nerve Preserving Vestibular Schwannoma Surgery in Patients With Neurofibromatosis Type 2

To investigate the outcomes from ipsilateral simultaneous or sequential cochlear implantation in patients with neurofibromatosis type 2 (NF2) after vestibular schwannoma removal with cochlear nerve preservation. Retrospective case series. Single tertiary referral NF2 center. Six patients with NF2. Removal of vestibular schwannoma (VS) with preservation of the cochlear nerve and cochlear implantation. Four patients had their surgery via a translabyrinthine approach. Two patients had a retrosigmoid approach. A cochlear implant was inserted at the same time as tumor removal in 4 cases and sequentially in 2 cases. Surgical and audiometric outcomes using Bamford-Kowal-Bench (BKB) and City of New York University (CUNY) sentence scores. The average age at implantation was 24 years (range, 15-36 yr). Follow-up ranged from 5 to 93 months, with an average of 38 months. All patients had useful hearing in the contralateral ear before surgery. One patient gained no benefit from cochlear implantation and proceeded to have an auditory brainstem implant. Of those that had functional cochlear nerves, the average BKB score in quiet was 64%, BKB score in noise was 42%, and CUNY score with lipreading was 97%. Results varied within the group, but all patients gained significant benefit and continue to use their CI at least intermittantly. The present series demonstrates that in selected cases, cochlear implantation can be successful after a translabyrinthine approach for VS removal and for restoring hearing after failed retrosigmoid hearing preservation surgery. All patients found the cochlear implant offered useful hearing even in the presence of contralateral hearing.

The far lateral approaches to the craniovertebral junction

Access to pathologies at the craniovertebral junction can be achieved with a number of approaches; all should avoid manipulation of the neural structures. In much the same way as an orbito-zygomatic approach is used to augment fronto-temporal access and reduce brain retraction and a trans-labyrinthine approach is chosen rather than a retrosigmoid approach to a vestibular schwannoma, so bone at the foramen magnum, including condyle, can be removed to improve access to structures ventral to the brainstem and the spinal cord. Large tumors may create a corridor of access allowing a more posterior approach to be employed. Smaller tumors and pathologies that do not distort the brain may, however, require more bone removal along with mobilization of the vascular structures, particularly the vertebral artery and occasionally the jugular tubercle. The far lateral approach with partial condylectomy and vertebral artery mobilization is described as the preferred access.

Ocena ryzyka uszkodzenia nerwu twarzowego i pogorszenia słyszenia u chorych operowanych z powodu guza nerwu przedsionkowo-słuchowego

AimTo compare hearing preservation possibilities and facial nerve outcomes between middle fossa (MF) and translabyrinthine (TL) approach in patients undergoing vestibular schwannoma surgery. Material and methodsRetrospective analysis of medical records of 104 patients treated otosurgically due to vestibular schwannoma. All patients underwent surgery using one of the two approaches: 41 MF and 63 TL. The risks of deterioration of the facial nerve function as well as hearing were evaluated. ResultsStatistical significance was found between the two surgical groups in hearing results, and no significance in facial nerve outcomes. In addition analysis revealed that facial nerve outcomes correlated with the size of the tumor. ConclusionsMiddle fossa approach offers possibility to resect vestibular schwannomas with hearing preservation. In case of translabyrinthine approach the hearing becomes permanently damaged due to the surgical technique. The risk of deterioration of facial nerve function correlates with the size of the tumor (larger the tumor bigger the risk), however, there is no correlation when it comes to surgical approach (Mf or TL).

Removal of Hydroxyapatite Cement From Cadaveric Temporal Bones After Transtemporal Surgery

To determine the best method of removing hydroxyapatite cement from the temporal bone in the postoperative period. The advent of hydroxyapatite cement in neurotologic surgery of the temporal bone has dramatically decreased the rate of postoperative cerebrospinal fluid leaks. However, there is no literature currently available on how to manage these patients in the setting of postoperative hematomas of the cerebellopontine angle. Nine cadaveric temporal bones were obtained that had previously undergone translabyrinthine approach drilling in an academic temporal bone lab. Fascia and adipose tissue were placed medial to the facial nerve and the temporal bone was then filled with hydroxyapatite cement to the level of the cortex. Removal of hydroxyapatite cement was undertaken using a Freer elevator, mastoid bone curette, and finally, a drill in sequential fashion. This occurred at 9 predetermined time intervals from 1 to 30 hours and was timed in each case. Removal using the freer and curette failed in each case, and the drill was ultimately used to remove the hydroxyapatite cement in all cases. The time to reach the packed fascia and adipose tissue varied from 3 to 6 minutes, average time is 4.27 ± 0.84 minutes. Although hydroxyapatite cement has dramatically decreased the rate of postoperative cerebrospinal fluid leak in translabyrinthine surgery, its use has also brought a new set of considerations. This study suggests that hydroxyapatite cement removal in the setting of postoperative hematoma after translabyrinthine surgery would require drilling rather than bedside incisional opening alone. Like standard craniotomy approaches, postoperative hemorrhage management requires intraoperative drainage.

Use of the translabyrinthine approach to repair congenital spontaneous cerebrospinal fluid leakage in five Chinese patients with Mondini dysplasia

ObjectivesTo introduce a more effective surgical technique for the repair of spontaneous incurable cerebrospinal fluid (CSF) leakage (CSF otorrhea). MethodsThe cases of five Chinese patients with Mondini dysplasia and CSF leakage were reviewed. All patients presented with rhinorrhea or otorrhea from childhood and recurrent meningitis attacks. CSF leakage was repaired surgically using the translabyrinthine approach. ResultsFacial paralysis occurred in the first two patients, but was cured 2 months later. The other three patients recovered well and had no facial paralysis or complication. CSF leakage did not recur in any patient after follow-up periods of 0.5–3 years. ConclusionMondini dysplasia with CSF leakage is rare. Adequate diagnosis and treatment are required to avoid life-threatening complications, such as meningitis. We recommend the translabyrinthine approach as an alternative surgical technique that reduces recurrence.

The translabyrinthine approach

Access to the cerebellopontine angle and petrous apex can challenge the most discerning skull base surgeon. Modern skull base surgery has evolved owing to advances in monitoring, instrumentation, and higher-resolution microscopy. This evolution is now accompanied by a greater expectation to preserve functional neurovascular and otological structures dependent on the approach and the pathology. The translabyrinthine approach has proven to be a reliable and safe option to access the internal acoustic canal and the cerebellopontine angle with sacrifice of the hearing mechanism. This article forms the foundation for further discussion regarding the transotic and transcochlear approaches to the petrous apex and beyond.

Trigeminal Nerve Deficit in Large/Compressive Acoustic Neuromas (ANs) and Its Correlation with MRI Findings

Objectives: Evaluate the risk of pre- and postoperative trigeminal nerve (V) impairment in large ANs. Determine predictive risk factors on pre- and postoperative MRIs. Methods: Retrospective study (1994-2009) including patients with stage 4 or 5 AN (classification of Zini-Magnan). All underwent surgical resection (chiefly translabyrinthine approach). Pre- and postoperative trigeminal symptoms were sought. Pre- and 3-month-postoperative MRIs were obtained. Results: Fifty-four patients (30 females, mean 51 years) were operated. Preoperatively, 3 patients (5.5%) had trigeminal neuralgia, 29 (54%) had trigeminal hypoesthesia (V1 < V2 = V3), and 16 (30%) had no corneal reflex (V1 branch). Postoperatively, 2 patients (4%) had trigeminal neuralgia, 1 (2%) had trigeminal anesthesia, 25 (46%) had trigeminal hypoesthesia (V1 = V2 = V3), 26 (48%) had no corneal reflex, and most also had House-Brackmann ≥ grade IV facial paralysis. Keratitis occurred in 42% of patients with absent corneal reflex postoperatively. After analyzing preoperative MRI, there was only one predictive factor of preoperative trigeminal impairment: impaction of the tumor on cerebellar peduncles ( P < 0.05). Postoperative trigeminal deficit was correlated with one finding on postoperative MRI: nonvisibility of V on MRI ( P < 0.05). Postoperative trigeminal deficit was correlated with one finding on preoperative MRI: impaction of the tumor on cerebellar peduncles ( P < 0.05). Conclusions: Trigeminal impairment in large/compressive ANs has to be sought particularly to avoid corneal complications. If the frequency of trigeminal hypoesthesia slightly diminishes after tumor removal, there is worsening of preoperative function of V1 and increased frequency of absent corneal reflex, also worsened by facial paralysis. We were able to correlate trigeminal involvement with pre- and postoperative MRI findings.

Use of bone anchoring device in electromagnetic computer-assisted navigation in lateral skull base surgery

Conclusion: The use of the bone anchoring device associated with a fiducial marker, both fixed close to the operating field, improves the reproducibility and effectiveness of the computer-assisted navigation in lateral skull base surgery. Objectives: Computer-assisted navigation in lateral skull base surgery using the electromagnetic system Digipointeur® needs an external fiducial marker (titanium screw) close to the operating field to increase position accuracy (PA) to about 1 mm. Displacement of the emitter placed in the mouth (Buccostat®) induces a drift of the system, leading to at least 20% of unsuccessful procedures. The aim of this study was to evaluate the PA, stability, and reproducibility of computer-assisted navigation in lateral skull base surgery using a bone anchoring device to provide a fixed registration system near the operating field. Methods: Forty patients undergoing a lateral skull base procedure with the Digipointeur® system performed with both the titanium screw and bone anchoring device were included in this prospective study. They were divided in two groups. In the first one (n = 9), the PA was measured before and after screw registration for five intratemporal landmarks, during a translabyrinthine approach. In the second group (n = 31), all lateral skull base procedures were included and the PA was evaluated visually by the surgeon on different landmarks of the approaches as well as the stability of the system. Results: In the first group, the PA was 7.08 ± 0.59 mm and 0.77 ± 0.17 mm (mean ± SEM, p < 0.0001) before and after screw registration, respectively. In the second group, the PA was considered as accurate by the surgeon in all cases and no drift of the system was observed. Computer-assisted surgery was never abandoned due to increased stability of the bone-anchored emitter.

Evaluation of intraoperative cone beam computed tomography and optical drill tracking in temporal bone surgery

A prototype system for intraoperative cone beam computed tomography (CBCT) imaging has been developed and augmented with real time optical tracking of a surgical drill. We hypothesize that this system provides sufficient accuracy for guidance of temporal bone surgery. Basic research. Measurements of drill localization accuracy using CBCT imaging were obtained with a custom three-dimensional calibration object. Integrated CBCT imaging and drill tracking were prospectively evaluated on 12 cadaver temporal bones. Six inexperienced and six experienced surgeons conducted four surgical tasks: cortical mastoidectomy, posterior tympanotomy, cochleostomy, and a translabyrinthine approach to the internal auditory canal. Questionnaires provided expert feedback on tracking accuracy and system usability. Target registration error measurements of drill tracking accuracy and precision yielded a mean of 0.76 mm, a maximum of 1.30 mm, and a standard deviation of 0.21 mm. Anatomical landmark identification tasks (e.g., facial nerve, incus, semicircular canals, cochlea) provided additional validation of system accuracy. The usability and utility of the guidance system were positively rated by both groups of surgeons, with further modifications underway to improve tracking line of sight and registration workflow. Experienced but in particular inexperienced surgeons indicated significant benefits in cases involving extensive disease, abnormal anatomy, and loss of anatomical landmarks. The integration of intraoperative CBCT imaging with optical tracking provides sufficient accuracy to localize anatomical structures within the temporal bone using an otological drill. Future studies will explore the role of this technology in complex oncological resections, in surgery for congenital anomalies, and as a tool for teaching.

End-to-Side Interposed Donor Grafting as a Facial Nerve Reinforcement Technique after Vestibular Schwannoma Surgery

This retrospective case review was performed to determine the facial function outcome of an end-to-side interposed donor grafting technique in patients who had a nonresponsive and partially injured facial nerve during a translabyrinthine approach for vestibular schwannoma resection. The study included patients with silent electrophysiological tests after partial injury of the facial nerve during translabyrinthine schwannoma resection surgery in a tertiary referral hospital. The patients underwent end-to-side interposed donor grafting as a facial nerve reinforcement technique, and we evaluated their facial function after 1 year of follow-up. Four cases with intact preoperative facial function were included (3 men and 1 woman). All patients had a lack of electrical response from the facial nerve and partial anatomic injury after a translabyrinthine approach. An end-to-side interposed donor grafting technique was performed. The donor grafts used were the sural nerve (2 patients), superior vestibular nerve (1 patient), and greater auricular nerve (1 patient). All patients achieved a good House-Brackmann grade. Ocular adjuvant procedures were performed in all patients. Immediate repair of the facial nerve with an interposed donor graft may provide better facial function in patients who have no electrical response from a partially injured facial nerve after vestibular schwannoma surgery.

Predictive factors influencing facial nerve outcomes in surgery for small-sized vestibular schwannoma

Conclusion: The most important predictive factor of facial nerve outcome in surgery for small-sized vestibular schwannoma (VS) is the adhesion between the tumor and the facial nerve. Objectives: To compare the facial nerve outcomes between middle cranial fossa (MCF) and translabyrinthine (TL) approaches, and to analyze the preoperative and intraoperative factors influencing facial nerve outcome after small VS surgery in our neurotologic department. Methods: A total of 29 patients were retrospectively analyzed, with 16 in the MCF group and 13 in the TL group. Facial function was serially evaluated according to the House-Brackmann classification at 7 days, 1 month, 3 months, 6 months, and 1 year postoperatively. The effects of variables such as the surgical approach, tumor size, nerve origin, extrameatal extension, intraoperative tumor adhesion to the facial nerve, and facial nerve displacement were determined. Results: Early and late facial nerve outcomes showed no significant correlation with surgical approach, tumor origin, tumor size, extrameatal extension, or facial nerve displacement pattern. However, a significant correlation was observed with tumor adhesion to the facial nerve and facial nerve outcomes.

Long-term facial nerve function following facial reanimation after translabyrinthine vestibular schwannoma surgery: A comparison between sural grafting and VII–XII anastomosis

The aim of this study was to compare the recovery of long-term facial nerve function between patients who received sural grafts and those who underwent hypoglossal-facial anastomosis techniques following translabyrinthine vestibular schwannoma surgery. This study included 25 patients with vestibular schwannomas treated with translabyrinthine tumor removal. All patients had large tumors with a mean tumor size of 3.12 cm. Of these patients, six had progressive tumor enlargement symptoms and had been treated previously with stereotactic irradiation. Preoperatively, all patients had normal facial functions, and total tumor removal with a translabyrinthine approach was achieved in all cases. During surgery, the facial nerve was interrupted in all 25 patients. Two types of facial reanimation were performed. Sural grafts were placed in 13 patients and hypoglossal-facial (VII–XII) anastomosis was performed in the other 12. Facial nerve function and surgical outcomes were observed upon discharge, in the short term (one year following surgery), and in the long term (three years following surgery). Total facial paresis was observed in all patients upon discharge. In the sural graft group, House-Brackmann grade III facial function was achieved in four patients upon short-term evaluation and in ten upon long-term evaluation, while House-Brackmann grade IV facial function was achieved in nine patients upon short-term evaluation and three in the long term. In the VII-XII anastomosis group, House-Brackmann grade III facial function was achieved in two patients in the short term and eight in the long term, and House-Brackmann grade IV facial function was achieved in ten patients in the short term and four in the long term. There was a statistically significant difference in the facial recovery results between the short- and long-term follow-up periods. The sural graft group exhibited a marked improvement in results compared with the VII–XII anastomosis group, but no statistically significant difference in facial function was observed between the two facial reanimation groups at either the short- or long-term follow-up. In the sural graft group, synkinesia, noted in three patients, was the most frequently observed complication. Claudication was common upon discharge (four patients), but diminished during follow-up. Disarticulation was the most common complication in the VII–XII anastomosis group (five patients); numbness of the tongue was the second most common complication (four patients). None of the patients developed dysphagia. Facial reanimation is an effective procedure for the surgical rehabilitation of static and dynamic facial nerve functions. Significant improvement in facial nerve function may occur more than three years after surgery. Despite morbidities such as synkinesia, the sural graft technique demonstrates greater improvements in facial nerve function than VII–XII anastomosis in the short and long term following surgery, but this conclusion requires confirmation by larger studies with a greater number of patients.

Delayed Otorrhea Following Translabyrinthine Craniotomy Approach to the Cerebellopontine Angle

Background: The translabyrinthine approach is most commonly used in the resection of internal auditory canal or cerebellopontine angle (CPA) tumors in patients with nonserviceable hearing preoperatively. Abdominal adipose tissue is typically used to obliterate the resulting dural defect. The risk of postoperative cerebrospinal fluid (CSF) leakage can be as low as 4%. Delayed leakage is rarely encountered, with the majority of CSF fistulae occurring within 5-7 days after surgery.

Facial Nerve Function after the Extended Translabyrinthine Approach

Facial Nerve Function after the Extended Translabyrinthine Approach

Outcome of translabyrinthine surgery for vestibular schwannoma in neurofibromatosis type 2

Objectives. To analyse the long-term outcome of translabyrinthine surgery for vestibular schwannoma (VS) in neurofibromatosis type 2 (NF2). Research type. Retrospective cohort study. Setting. Two tertiary referral NF2 units. Patients. One hundred and forty eight translabyrinthine operations for patients with VS were performed. Preoperative stereotactic radiotherapy had been performed on 12(9.4%) patients. Results. Mean tumour size was 3.1 cm. Total tumour excision was achieved in 66% of cases, capsular remnants were left in 24% of cases, and subtotal excision was achieved in 5% and partial removal was achieved in 5%. The radiological residual/recurrence rate was 13.9%. The perioperative mortality was 1.6%. At 2 years postoperatively, facial function was expressed in terms of House–Brackmann score (HB): HB 1 in 53.4%, HB 1/2 in 61.3%, HB 1–3 in 83.2% and HB 4–6 in 16.8%. All nine patients who underwent surgery following failed stereotactic radiotherapy had HB 3 function or better. Among 9.5% of the cases, 14 facial nerves were lost during surgery and repaired using direct anastomosis or grafting. There was no tinnitus present preoperatively in 27% of the cases, and 22% of patients developed tinnitus postoperatively. In patients with preoperative tinnitus, 61% remained the same, 17% got it resolved and only in 21% it worsened. The preoperative hydrocephalus rate was 26%, and among 15% of the cases five ventriculo-peritoneal (VP) shunts were performed. The cerebrospinal fluid leak rate was 2.5%. Fifty-six patients underwent auditory brainstem implantation (ABI) and two patients had cochlear implant (CI) sleepers inserted. Conclusions. The management of patients with NF2 presents the clinician with a formidable challenge with many patients still presenting themselves late with the neurological compromise and a large tumour load. There is still an argument for the management by observation until the neurological compromise dictates interventional treatment particularly with the option of hearing rehabilitation with ABI or CI. The translabyrinthine approach provides a very satisfactory means of reducing the overall tumour volume.

Oxygenated fixation demonstrates novel and improved ultrastructural features of the human endolymphatic sac

The purpose of the present study is to describe in detail the ultrastructure of the human endolymphatic sac using a new and improved method of fixation as well as a refined surgical approach in obtaining specimens. Transmission electron microscopy of the human endolymphatic sac, employing an oxygenated fixative. Eighteen tissue samples of the human endolymphatic sac were obtained during surgery for vestibular schwannoma using the translabyrinthine approach. The specimens were fixed in 2% glutaraldehyde in an oxygenated fluorocarbon blood substitute vehicle before preparation by routine methods for transmission electron microscopy. We focused on the epithelial cell layer, subepithelial tissue, intraluminal content, and vascular tissue in both the intra- and extraosseous part of the endolymphatic sac. We observed well-defined endolymphatic sac epithelial cell lining in all 18 specimens. In general, we found very well-preserved specimens with well-defined intracellular structures. In contrast to the results in former studies, a minimum of fixation artifacts was observed in the present study. Three different cell types were observed in the intraosseous part of the sac: mitochondria-rich cells, ribosome-rich cells, and nonclassifiable cells. A fourth cell type was found in the extraosseous part. Novel ultrastructural features of the epithelial lining and the subepithelial layer are described and discussed. The results in the present study indicate an improvement in obtaining human tissue with optimal fixation for ultrastructural analysis and provide several novel morphologic observations. The potential functions of the endolymphatic sac are discussed with reference to former studies.

Editorial

Figure: William F. House, DDS, MDFigure: Mr. WilsonFigure: Dr. BrackmannFigure: Dr. ZengIt is with great sadness that we note the death of William F. House, DDS, MD. Dr. House died at his home in Aurora, OR, on Dec. 7, 2012, six days after he turned 89. “Dr. Bill” is widely known and admired as the father of neurotology for his key role in the development of safe and effective treatments for hearing and balance disorders. He was the first to use a microscope in neurosurgery, and he developed the middle fossa approach and then the translabyrinthine approach for the removal of acoustic neuromas. As a result, the mortality rate for acoustic neuroma operations dropped from 40 percent to less than 1 percent, where it now stands. Prior to Dr. Bill's innovations, preservation of hearing or facial nerve function was not even a goal in acoustic neuroma treatment. Now, virtually all patients have facial nerve function preserved, and many maintain their hearing as well. Dr. Bill's crowning achievement is the development of the first practical cochlear implant (CI). Three large steps led to the development and success of present-day CIs: (1) the pioneering step to implant the first patients with a safe and reliable device that had a life span of many years, (2) the development of devices that provided multiple sites of stimulation in the cochlea to take advantage of the tonotopic organization of the auditory system, and (3) the development of processing strategies that utilized the multiple sites and supported high levels of speech recognition for most users of cochlear implants. More than anyone else, Dr. Bill was responsible for that critical first step. At the outset, many experts opposed cochlear implants, arguing that any useful restoration of hearing with electrical stimulation was a fool's dream. As a result, implantation in humans, particularly children, was considered unethical, as the surgical risks could not be outweighed by any conceivable benefit from the CI. The criticism was vociferous, but Dr. Bill persevered, determined to help deaf people. “The thing that kept me going was that patients could hear, and they told me how much they appreciated it,” he said on Oct. 18, 2012, during his last published interview. (See HJ 2012;65[12]:32 or http://bit.ly/DrBillArticle for the print article, and http://bit.ly/DrBillVideo for the video.) “We implanted a number of children who were 2 or 3 years of age, and one of them even became a linguist.” Without Dr. Bill's determination and pioneering contributions, the development of the cochlear implant would have been greatly delayed, if started at all. We as a field and the hundreds of thousands of deaf and severely hearing-impaired people who have benefitted from CIs owe him the greatest debt of gratitude. His work should serve as a constant reminder: We all stand on the shoulders of giants. CORRECTION In the January issue, in the article “Task Force Finding Underscores Knowledge Gap about Benefits of Hearing Screening,” the title for Jaynee A. Handelsman, PhD, was incorrect. She is director of pediatric audiology at the University of Michigan C.S. Mott Children's Hospital.

Endolymphatic sac tumors: experience of three cases

To describe the clinical features, radiological findings, treatment and outcomes of three cases of endolymphatic sac tumors (ELST). Retrospective analysis of three cases of ELST. The first patient had a large ELST invading the labyrinth after a long history of vertigo. He was recurrence-free 1 year after retrolabyrinthine surgical removal. In the second case, an acute peripheral facial nerve paralysis associated with ipsilateral sensorineural hearing loss led to the diagnosis. A translabyrinthine approach was used to remove the tumor, which recurred three times over 10 years. The third patient was a young woman suffering from von Hippel-Lindau (VHL) disease and referred for a sudden sensorineural hearing loss due to an intralabyrinthine hemorrhage secondary to a 2 mm-large endolymphatic sac-confined ELST. Her hearing was totally lost after the deafness recurred 1 month after this first episode. MRI demonstrated a small bilateral ELST. The patient refused surgery on the deaf side. ELST are difficult to diagnose due to the wide variety of their presentations. Patients with ELST should be screened for VHL disease. Dural invasion and tumor hypervascularization increase the risk of local recurrences after surgery. Early surgical resection may lead to complete tumor removal and inner ear preservation.

Expression of Anion Exchangers in Cultured Human Endolymphatic Sac Epithelia

Pendrin acts as a Cl-/HCO3- exchanger and is responsible for endolymphatic fluid volume and pH homeostasis in human endolymphatic sac epithelial cells. The endolymphatic sac (ES) is part of the membranous labyrinth in the inner ear that plays an important role in maintaining homeostasis of the endolymphatic fluid system. However, the exact mechanism of fluid volume and pH regulation is not fully understood yet. We aimed to demonstrate the expression of various anion exchangers (AEs), including pendrin, in cultured human endolymphatic sac epithelial (HESE) cells. Endolymphatic sac specimens were harvested during acoustic neuroma surgery (n = 24) using the translabyrinthine approach and then subcultured with high epidermal growth factor (EGF) (25 ng/ml) media and differentiated using low-EGF (0.5 ng/ml) media. The cultured cells were classified according to the morphology on TEM. The Cl-/HCO3- exchanger activity was assessed by pHi measurement using pH sensitive dye 2', 7'-bis (2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF/AM). We performed reverse transcriptase-polymerase chain reaction and immunohistochemical staining for AEs. We determined that 7.3 ± 6.7% of cells differentiated into mitochodria-rich cells and 50.2 ± 15.1 of cells differentiated into ribosome-rich cells. bAE3, AE4, SLC26A4, SLC26A6, and SLC26A11 were also expressed in cultured HESE cells. The cultured cells had Cl-/HCO3- and Cl-/formate exchange activity on the luminal membrane, which is sensitive to anion channel inhibitors (DIDS 500 μM). Furthermore, we showed that pendrin (SLC26A4) was expressed in cultured HESE cell membranes. Our results suggest that AEs, including pendrin, are expressed in epithelia of ES and may have role in maintaining ionic homeostasis, and the HESE culture system are useful for uncovering the functional role of ES epithelial cells.

Unilateral internal auditory canal stenosis with progressive facial weakness

Internal auditory canal (IAC) stenosis is a rare cause of sensorineural hearing loss. Patient may present with symptoms of progressive facial nerve palsy, hearing loss, tinnitus and giddiness. High resolution temporal bone CT-scan and magnetic resonance imaging (MRI) are the important tools for diagnosis. No specific management has been devised. Here is presentation of a case of unilateral (left) IAC stenosis with profound hearing loss and progressive House Brackmann Grade III-IV facial weakness. The diameter of the IAC was less than 2 mm on high resolution temporal bone computed tomography (HRCT) scan. It was managed by facial nerve decompression by translabyrinthine approach in an attempt to prevent further deterioration of facial palsy. DOI: http://dx.doi.org/10.3329/bjo.v18i2.12014 Bangladesh J Otorhinolaryngol 2012; 18(2): 179-182