Bilateral Narrow Internal Auditory Canal With Duplication: High Resolution CT And MRI Findings

Inner ear malformations account for only 20 % of cases of congenital sensorineural hearing loss.A narrow internal auditory canal (IAC) with duplication is a very rare congenital anomaly that can be associated with other malformative ear abnormalities. Identification and characterization of these abnormalities will be crucial for the proper management of patients.We report two cases of bilateral duplicated internal auditory canal with other associated inner ear anomalies.

Estenosis congénita aislada del conducto auditivo interno como causa de hipoacusia neurosensorial unilateral y paresia del nervio facial / Congenital internal auditory canal stenosis presenting with unilateral sensorineural hearing loss and facial nerve dysfunction

RESUMEN La estenosis del conducto auditivo interno con aplasia/hipoplasia del nervio cocleovestibular es una patología muy infrecuente. Suele ser unilateral y puede acompañarse de aplasia/hipoplasia del nervio facial y otras malformaciones del oído interno. Se presentan aquí dos casos clínicos de pacientes pediátricos con estenosis del conducto auditivo interno unilateral con compromiso del séptimo y octavo par craneal ipsilateral. Se describen las historias y evaluaciones clínicas, hallazgos audiovestibulares, hallazgos imagenológicos, tratamientos indicados y sus resultados.

ABSTRACT Congenital internal auditory canal stenosis associated with aplasia/hypoplasia of the cochleovestibular nerve is a very infrequent pathology. It is usually unilateral and may be accompanied by aplasia/hypoplasia of the facial nerve and other malformations of the inner ear. We hereby present two clinical cases of pediatric patients with congenital internal auditory canal stenosis, with involvement of the seventh and eighth ipsilateral cranial nerve. The medical histories and clinical evaluations, audiovestibular findings, imaging findings, treatments and their results are described.

Duplicated Internal Auditory Canal: High-Resolution CT and MRI Findings

OBJECTIVE: To summarize the high-resolution computed tomography (HRCT) and magnetic resonance imaging (HRMRI) features of duplicated internal auditory canals (DIACs). MATERIALS AND METHODS: Ear HRCT data of 64813 patients with sensorineural hearing loss (SNHL), obtained between August 2009 and November 2017, were reviewed. Among these patients, 12 (13 ears) were found to have DIACs, 9 of whom underwent HRMRI. Their images were evaluated by two otoradiologists. RESULTS: The rate of occurrence of DIAC among SNHL patients was 0.019% (12/64813). The internal auditory canals of 13 ears were divided into double canals by complete (n = 6) and incomplete (n = 7) bony septa, with varied orientations ranging from horizontal to approximately vertical. All of the anterosuperior canals extended into the facial nerve (FN) canal, except for 1, which also extended to the vestibule. The posteroinferior canals ended in the cochlea and vestibule, except for 2, which also connected to the FN canals. Magnetic resonance images revealed that 77.8% (7/9) and 22.2% (2/9) of vestibulocochlear nerves (VCNs) were aplastic and hypoplastic, respectively. Furthermore, 88.9% (8/9) of FNs were normal, except for 1, which was hypoplastic. All of the affected ears also had other ear anomalies: a narrow, bony cochlear nerve canal was the most common other anomaly, accounting for 92.3% (12/13). Malformations of other systems were not found. CONCLUSION: Double-canal appearance is a characteristic finding of DIAC on HRCT, and it is usually accompanied by other ear anomalies. The VCN usually appears aplastic, with a normal FN, on HRMRI.

Limitation of High Pitch Sound Perception in Nontumor Patients with Auditory Brainstem Implantation / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Auditory brainstem implantation (ABI) is another option for hearing rehabilitation in non-neurofibromatosis type 2 patients who cannot undergo cochlear implantation (CI). However, the average performance of ABI is worse than that of CI. We analyzed the psycho-electrical parameters of each electrode and psycho-acoustic response to different frequency sounds in nontumor patients with ABI. SUBJECTS AND METHOD: Sixteen patients with ABI from July 2008 to May 2013 were included in the study. They were followed up for 4 to 56 months. Among them, 12 were prelingual deaf with a narrow internal auditory canal or cochlear ossification. The remaining four were post-lingual deaf adults with severely ossified cochleae. We analyzed the electrical parameters [impedance, threshold level (T level), and dynamic range] of each of the 12 electrodes. We also evaluated the sound field pure-tone threshold, Ling 6 sound detection-identification test (Ling 6 test), and pitch ranking data of these patients. RESULTS: The impedance, T level, and dynamic range did not significantly differ among electrodes. However, the pure-tone threshold to sound field stimulation was elevated in the high tone area, where more variables were found than in the low frequency area. Patients could not identify /S/ and /Sh/ sounds in the Ling 6 test. The mean T level and the dynamic range of the three highest pitch-perceiving electrodes in each patient was higher and narrower, respectively, than those of the three lowest pitch-perceiving electrodes. CONCLUSION: The nontumor patients with ABI have difficulty perceiving high pitch sound. More sophisticated penetrating type electrodes and, if possible, bimodal stimulation with CI, could be considered.

MRI in Cerebellopontine angle and internal auditory canal lesions

Background: A large variety of inflammatory and neoplastic lesions are known to occur within internal auditory canal and cerebellopontine angle Imaging techniques are now available to guide the search for the underlying cause of most patient complaints The advent of MRI has revolutionized the medical diagnostic imaging because it allowed tissue characterization of many lesions High resolution MRI scan is highly sensitive in detecting lesions of internal auditory canal and cerebellopontine angle More recently, diffusion imaging is playing a substantial role in evaluation of CPA masses High ADC values of solid vestibular schwannomas were in conformity with increased diffusion rates, indicating the presence of increased amounts of extracellular water (a relatively loose tissue in tumor matrix) This study was undertaken with purpose to present MRI findings in cases of CPA and IAC lesions and to assess the impact of MRI on the diagnosis management and follow up, after treatment, of these lesions with an attempt to compare MRI findings with operative and H/P findings in the cases where surgery was done Materials and methods: The present study was conducted in Post Graduate Department of Radiodiagnosis, Government Medical College, Srinagar on patients presenting with otoneurological signs and symptoms suggestive of CP angle and IAC lesions referred for MR imaging by various departments of GMC Hospital Srinagar during the one year period of study Results: Majority of lesions found in this study were tumors (33 lesions), next common in our series were inflammatory lesions and vascular lesions (4 each case) Among all lesions and tumors most common MR diagnosis in our study was acoustic neuroma 20 of 41 lesions (4878%) and 20of 33 tumors (6060%) respectively Next common among tumors was meningiomas 3 out of 33 cases (909%) Conclusion: The results of the present study concluded that, MRI has particular advantages over CT for study of internal auditory canal and cerebellopontine lesions because it is non-ionizing Aijaz Ahmad Hakeem, Irshad Mohiuddin MRI in Cerebellopontine angle and internal auditory canal lesions IAIM, 2018; 5(12): 40-50 Page 41 investigation, better soft tissue contrast and resolution, multiplanar capability permits more reliable distinction of lesions, better identification of structures involved by lesions, tissue characterization of lesions and absence of beam hardening artifacts makes MR imaging superior ion evaluating the lesions in CP angle and IAC The radiological features of various lesions are often sufficiently distinctive to permit a specific diagnosis to be made MR imaging due to its multiplanar capability helps in knowing the exact site and extent of these lesions MRI shows inflammatory and vascular lesions with exquisite detail and is better for detection of such lesions as compared to CT MRI allows a confident perspective pathologic diagnosis to be made (Using FSE T2 weighted images, diffusion imaging, SE images, thin section post gadolinium scans) and this predictive value far exceeded the CT

Localization of internal auditory canal in the middle cranial fossa approach: a study in Chinese based on CT reconstruction technique / 上海交通大学学报（医学版）

Objective • To study how to localize the internal auditory canal in the middle cranial fossa approach in Chinese using CT reconstruction technique. Methods • Forty-four cases (88 sides) of normal temporal bone CT data were selected, including 22 males and 22 females. The anatomical structures of the middle cranial fossa including the skull base, the internal auditory canal and the superior semicircular canal were reconstructed in 3D. The angle between great superficial petrosal nerve and internal auditory canal, the angle between superior semicircular canal and internal auditory canal and the osseous thickness above internal auditory canal were measured. The angle and distance were statistically analyzed in different sex and side groups. Results • On the reconstructed 3D middle cranial base, the arcuate eminence could only be identified in 43% cases. The angle between great superficial petrosal nerve and internal auditory canal was 51.46˚±9.28˚; the angle between superior semicircular canal and internal auditory canal was 49.22˚±7.32˚; the osseous thickness above internal auditory canal was (4.38±0.97) mm. No gender or side difference was noticed. Conclusion • There are significant individual differences in angulation and distance between the internal auditory canal and its related anatomical structures. CT reconstruction technique is helpful for accurate localization of the internal auditory canal.

Clinical analysis of non-acoustic lesions in internal auditory canal and cerebellopontine angle / 中国耳鼻咽喉头颈外科

OBJECTIVE To analyse the diagnosis of non-acoustic lesions in internal auditory canal(IAC) and cerebellopontine angle(CPA),and discuss the effects of imaging examinationon differential diagnosis.METHODS A retrospective study was carried out in 185 patients with non-acoustic lesions of IAC and CPA from January 2001 to December 2016,in which lower cranial schwannoma,facial nerve tumor,meningioma,cholesteatoma,malignant tumor,trigeminal schwannoma,cavernous hemangioma,arachnoid cyst,lipoma were diagnosed in 65,55,25,9,9,8,6,5 and 3 patients,respectively.All patients were performed surgeries,and preoperative diagnosis and surgical approach were decided according to clinical manifestation,CT and MRI findings.Postoperative diagnosis were confirmed by pathological examination.RESULTS Total removal of lesion was achieved in 185 patients [96 men and 89 women,11-77 years old,mean age (46.4±25.6) years] and mean follow-up time was (5.1 ±3.2) years.Postoperative complication was leakage of cerebrospinal (4 patients,2.2％).4 patients with malignancy were dead and 1 patient with cholesteatoma was found recurrent during the follow-up.All kinds of non-acoustic lesions in IAC and CPA had its characteristic imaging findings.Preoperative diagnostic accuracy rate was 93.5％(173/185).CONCLUSION Accurate preoperative diagnosis has great significance in developing treatment strategy for IAC and CPA lesions;Preoperative diagnosis should be achieved according to clinical manifestation,CT and MRI findings,which can significantly improve the accuracy rate of diagnosis.

Anatomical observation and measurement of bone labyrinth and internal auditory canal / 重庆医学

Objective To conduct the anatomical observation and measurement on adult temporal bone labyrinth and internal auditory canal structures to accumulate the anatomical data and provide anatomical basis for clinical internal ear surgery.Methods Thirty sides(left 16 and right 14)of adult dry temporal bone labyrinth and internal auditory canal structures were anatomically observed and the related structures were measured.Results (1) The specimen observation:the vestibule was egg conical cavity,and angle between long axis and sagittal plane was about 33°.The floor of internal auditory canal were divided into four districts,which angle between the inferior surface and vestibule was about 90°,the connection between tractus spiralis foraminosus bone crest of cochlea area and inguinal ring of cochlear spiral canal was the same rotated laps.(2)The data measurement:the comparison of means in various measurement items had no statistical differences between the left side and right side(P＞0.05);the comparison of mean length and crus distance had statistical differences among superior semicircular canal,posterior semicircular canal,lateral semicircular canal(P＜0.05);the comparison of means had statistical difference among posterior semicircular canal and superior semicircular canal,lateral semicircular canal(P＜0.05),but the comparison of means had no statistical difference between superior semicircular canal and lateral semicircular canal(P＞0.05).Conclusion The means of various measurement items in bone labyrinth and internal auditory canal have no difference between the left side and right side;the comparison of length means:posterior semicircular canal＞superior semicircular canal＞lateral semicircular canal;the comparison of crus distance means:superior semicircular canal＞ lateral semicircular canal＞posterior semicircular canal;the comparison of diameter means:posterior semicircular canal＞superior and lateral semicircular canal,but the diameter has no difference between superior semicircular canal and lateral semicircular canal.

Surgical exposure of the internal auditory canal through the retrosigmoid approach with semicircular canals anatomical preservation / Avaliação da exposição do fundo do conduto auditivo interno através do acesso retrosigmóide-transmeatal

Objective Evaluate the feasibility of an adequate exposure with anatomical preservation of labyrinth structures through retrosigmoid transmeatal approach (RSA) in surgeries for resection of acoustic neuromas/vestibular schwannomas (VS). Method Thirty patients underwent surgical resection and were preoperatively evaluated with fine slice high definition CT scans and 3D-MRI volumetric reconstructions. Extension of internal auditory canal (IAC) opening during surgery was measured using 3 mm right-angle calibrated hook and neuronavigation parameters. Postoperatively, the extension of IAC opening and integrity of the labyrinth were confirmed through preoperatively images procedures. Results The preoperative length of IACs varied between 7.8 and 12.0 mm (mean 9.3 mm, SD 0.98, 95%CI 8.9 to 9.6, and median 9.0 mm). Postoperative images demonstrated adequate opening of the IAC and semicircular channels integrity. Conclusion A complete drilling of the posterior wall of IAC through the RSA is feasible and allows direct visualization of the IAC-fundus without damaging the semicircular canals. .

Objetivo Avaliar a possibilidade de exposição adequada preservando anatomia das estruturas labirínticas pelo acesso retrosigmóide-transmeatal (RSA) nas ressecções de schwannomas do vestibular (VS). Método Trinta pacientes foram submetidos à ressecção cirúrgica e avaliados no pré-operatório com tomografias de alta definição e reconstruções de ressonância magnética 3D. A extensão da abertura do conduto auditivo interno (CAI) foi medida e confirmada com parâmetros de neuronavegação. No pós-operatório, a extensão da abertura e a integridade do labirinto foram confirmadas por imagens de tomografia computadorizada. Resultados A extensão do CAI no pré-operatório apresentou variação de 7,8-12 mm (média 9,3 mm, DP 0,98, IC95% de 8,9-9,6 e mediana 9 mm). Imagens pós-operatórias demonstraram abertura adequada do IAC e integridade dos canais semicirculares. Conclusão A abertura completa da parede posterior do CAI pelo RSA é possível e permite a visualização direta do fundo do conduto sem prejudicar os canais semicirculares. .

Bilateral Internal Auditory Canal Metastasis of Non-small Cell Lung Cancer / Journal of the Korean Cancer Association, 대한암학회지

We report on a patient with brain metastasis involving bilateral internal auditory canal from non-small cell lung cancer (NSCLC). A 49-year-old woman who had been diagnosed with NSCLC (T2aN1M0) complained of persistent vertigo and bilateral tinnitus for three months. The patient had refused all treatments, including surgery and chemotherapy; however, she sought alternative medicine. The patient's hearing loss showed rapid progression bilaterally, and rotatory vertigo with peripheral-type nystagmus developed. Magnetic resonance imaging of the brain showed irregular nodular enhancement within both internal auditory canals with leptomeningeal enhancement and multiple intracranial metastasis. The patient was treated with epidermal growth factor receptor-tyrosine kinase inhibitor, and the tumor showed partial response. This was a rare case of multiple brain metastases involving bilateral internal auditory canal from known NSCLC presenting with vertigo and hearing loss.

A Case of Arachnoid Cyst in the Internal Auditory Canal / 대한이비인후과학회지

Arachnoid cysts are intra-arachnoid collections of cerebrospinal fluid; congenital in origin, they account for about 1% of all atraumatic intracranial mass lesions. Arachnoid cysts confined to the internal auditory canal are extremely rare. In most patients who has arachnoid cysts in the internal auditory canal, no direct intervention is necessary, but if the neurologic symptoms are progressive, the arachnoid cyst could be drained surgically to relieve the symptoms caused by compression of structures adjacent to the cyst. We present one case of a arachnoid cyst in the left internal auditory canal which was diagnosed by a temporal bone magnetic resonance imaging.

Morphologic measurement of entry points and landmarks of retrosigmoid approach using volume rendering with thin-section computed tomography and its significance / 吉林大学学报(医学版)

Objective To research the jugular foramen,internal auditory pore (IAP)and the turning point between its components by imageological methods and to provide theoretical basis for retrosigmoid approach in the operation of acoustic neurinoma.Methods The skulls of 100 volunteers were scanned to get the final result with thin-section computed tomographic image. High-resolution spiral CT multiplane reformation was used to reform images that were parallel to the Frankfort horizontal plane to measure the distance between the turning point of retrosigmoid (A),the edge of jugular foramen(B)and the lower edge of the internal auditory canal(C)(denoted AC,AB,BC) and the shortest distance from the jugular foramen to AC.The angles between AC,AB and sagittal axis(α,β) were measured.Results The distance of AC was (44.94 ± 3.84)mm,the distance of AB was (43.68 ± 4.56)mm.The distance of BC was (6.15 ±2.04)mm,and the shortest distance between jugular foramen and AC was (5.21±0.23)mm.The angleαwas measured as (39.50±4.74)°,and the angleβwas measured as (46.35± 5.51)°.Conclusion The research measure the distance and angle between entry points and landmarks of retrosigmoid approach and the safe distance.

Evaluation of Internal Auditory Canal Structures in Tinnitus of Unknown Origin

OBJECTIVES: The aim of the present study was to evaluate the internal auditory canal (IAC) and the nerves inside it to define possible structural differences in cases with subjective tinnitus of unknown origin. METHODS: Cases applying to the ear, nose and throat department with the complaint of tinnitus with unknown origin and having normal physical examination and test results were included in the study (n=78). Patients admitted to the radiology clinic for routine cranial magnetic resonance imaging (MRI) and whose MRI findings revealed no pathologies were enrolled as the control group (n=79). Data for the control group were obtained from the radiology department and informed consent was obtained from all the patients. Diameters of the IAC and the nerves inside it were measured through enhanced images obtained by routine temporal bone MRIs in all cases. Statistical evaluations were performed using Student t-test and statistical significance was defined as P<0.05. RESULTS: Measurements of IAC diameters revealed statistically significant differences between the controls and the tinnitus group (P<0.05). Regarding the diameters of the cochlear nerve, facial nerve, inferior vestibular nerve, superior vestibular nerve, and total vestibular nerve, no statistically significant difference was found between the controls and the tinnitus group. CONCLUSION: Narrowed IAC has to be assessed as an etiological factor in cases with subjective tinnitus of unknown origin.

Cochlear Implant Failure due to Cochlear Nerve Deficiency in a Child with Normal Internal Auditory Canal / 대한이비인후과학회지

The cochlear nerve, which propagates electrical signals to the auditory cortex, must function well for successful cochlear implantation. A narrow internal auditory canal (IAC) increases the risk of hypoplasia or aplasia of cochlear nerve, which may result in the failure of cochlear implantation. Therefore, a functioning cochlear nerve must be verified before deciding to do cochlear implantation by means of behavioral audiometry, electrophysiologic tests, or imaging studies in cases with narrow IAC. On the other hand, a candidate with a normal IAC can be overlooked in investigating the presence of functioning cochlear nerve. Because normal IAC does not always guarantee the presence of normal cochlear nerve, the functioning cochlear nerve should be proved prior to cochlear implantation in those cases. We report on a child, who had normal IAC and cochlea but failed auditory stimulation after cochlear implantation, and who was diagnosed as having cochlear nerve deficiency through retrospective review.

Solitary Metastasis of Bronchogenic Adenocarcinoma to the Internal Auditory Canal: A Case Report

We report a patient with an isolated metastasis to the internal auditory canal (IAC) of bronchogenic adenocarcinoma. A 58-yr-old man who had received 6-cycle of chemotherapy under diagnosis of non-small cell lung carcinoma (T4N2M0) two years ago was referred to our department with vertigo, right-sided facial paralysis and right-sided hearing loss. A provisional diagnosis of vestibular schwannoma or meningioma involving right IAC was made from magnetic resonance imaging. The patient underwent a translabyrinthine removal of the tumor. Histopathological study of the resected lesion showed a poorly differentiated adenocarcinoma compatible with bronchogenic origin. The patient died 9 months after surgery from extensive brain metastasis despite postoperative radiation therapy. In patients with a previous history of treatment of malignancy elsewhere in the body, the possibility of IAC metastasis must be considered when an IAC lesion is detected.

A Case of Cholesteatoma Extended Both into the Cochlea and IAC / 대한이비인후과학회지

Labyrinthine fistula caused by cholesteatoma can make various complications according to the site of the lesion. The lateral canal, superior canal ampulla, posterior canal and promontory of the cochlea are the common areas of fistulization. However, invasion into the cochlea or internal auditory canal (IAC) is very rare. We have experienced a case of cholesteatoma extending into the cochlea and IAC, which was successfully treated via the transotic approach. Herein we report this case with a review of literature

A case report of narrow internal auditory canal: Parasagittal reconstruction / 대한이비인후과학회지

A narrow internal auditory canal(IAC) is a malformation of the temporal bone, which is defined as IAC diameter of only 1-2mm in high resolution computed tomography(HRCT). This syndrome is known to be caused by aplasia or hypoplasia of the vestibulocochlear nerve. We present a case of unilateral narrow IAC which was diagnosed by HRCT. The aplasia of vestibulocochlear nerve was confirmed using MRI with parasagittal reconstruction images. The IAC was composed of two separate canals, one of which had facial nerve and the other an empty space by aplasia of the vestibulocochlear nerve.

16-slice Spiral CT Investigation of Bony Canals of the Internal Auditory Canal Fundus with Multiplanar Reformation / 实用放射学杂志

Objective To investigate 16-slice spiral CT findings of bony canals of the internal auditory canal ( IAC ) fundus withmultiplanar reformation (MPR) and provide evidence for dignosis of lesions in the IAC fundus and surgery.Methods CT scan of thetemporal bone was performed in 30 volunteers. Bony canals of the IAC fundus were measured in images acquired with MPR.Results The mean?SD measurements (in mm) of the anteroposterior diameter and superoinferior diameter of fundus of the IAC was (4.07?0.97) mm and (3.24?0.88) mm respectively. The mean?SD measurements (in mm) of the length and width of bony canal for the labyrinthinesegment of the facial nerve was (3.04?0.52) mm and (0.96?0.31) mm, respectively. The mean?SD measurements (in mm) of the length and width of bony canal of the superior vestibular nerve was (2.52?0.48) mm and (0.83?0.30) mm respectively. The mean?SD measurements (in mm) of the length and width of bony canal of the cochlear nerve was (0.89?0.19) mm and (2.05?0.39) mm respectively. The mean?SD measurements ( in mm ) of the length and width of bony canal of the inferior vertibular nerve was ( 1.07?0.23 ) mm and (0.73?0.21) mm respectively. The mean?SD measurements ( in mm ) of the length and width of singular canal was (3.56?0.68) mm and (0.56?0.11) mm respectively . Conclusion MPR with 16-slice spiral CT can demonstrate the shape and measurements of the IAC fundus,which would contribute in dignosis of lesions in the IAC fundus and surgery.