Anatomical Study of the Facial Recess with Implications in Round Window Visibility for Cochlear Implantation: Personal Observations and Review of the Literature

Abstract Introduction Posterior tympanotomy through facial recess (FR) is the conventional and most preferred approach to facilitate cochlear implantation, especially when the electrode is inserted through the round window. The complications of the FR approach can be minimized by proper understanding of the anatomy of the FR. Objective The present study was undertaken to assess the various parameters of FR and round window visibility, which may be of relevance for cochlear implant surgery. Methods Thirty-five normal wet human cadaveric temporal bones were studied by dissection for anatomy of FR and posterior tympanum. Photographs were taken with an 18megapixels digital camera, which were then imported to a computer to determine various parameters. Results The mean distance from the take-off point/crotch of the chorda tympani nerve (CTN) to the stylomastoid foramen was 4.08 ± 0.8 mm(range of 2.06 - 5.5mm). The variations in the course of the CTN included origin at the level of the lateral semicircular canal. Themean chorda-facial angle in our study was 26.91° ± 1.19°, with a range of 25° to 28.69°. The mean FR length ranged between 9.4 mm and 18.56 mm (mean of 12.41 ± 2.91mm) and varied with the origin of the CTN and pneumatization of temporal bone. The average maximum width of the FR was 2.93 ± 0.4 mm (range 2.24-3.45 mm) and the mean width of the FR at the level of the round window was 2.65 ± 0.41 mm. Conclusion The FR approach provides good access to the round windowmembrane in all cases. In some cases, table adjustment is required.

Association between taste perception, nutrient intake, and mental health in young Japanese women

BACKGROUND/OBJECTIVES: Taste perception is influenced by both nutritional factors and psychological factors. This study was undertaken to measure the 4 basic taste perceptions, nutrient intake, and mental health, and to examine the factors that affect insensitive taste perception in young Japanese women. SUBJECTS/METHODS: Young women in their late teens and twenties were enrolled as subjects. Taste perception was measured by applying the filter-paper disc method over areas of the chorda tympani nerve. Nutritional status was evaluated using brief, self-administered diet history questionnaires. The index of nutritional status was based on the 2015 Japanese dietary reference intakes. Mental health was assessed using the Japanese translation of the Profile of Mood States short version. This study was approved by the ethical committee at Osaka University. RESULTS: The normal taste perception group (four basic tastes [sweet, salty, sour, and bitter] identified as normal taste perception) comprised 55.4% of the subjects, while the abnormal taste perception group (more than 1 abnormal taste perception was perceived, regardless of flavor) comprised 44.6% of the subjects. There were no significant differences in nutrient intake (except manganese) and mental health between the normal and abnormal taste perception groups. Subjects who took 5 mg to less than 7.1 mg zinc per day were at significantly decreased risk of insensitive taste perception compared to subjects who consumed less than 5 mg zinc per day [Regression coefficient 0.831, 95% confidence interval 0.694–0.996]. CONCLUSION: The present results suggest that insensitive taste perception could be associated with zinc deficiency in young women in their late teens and twenties.

The electrophysiological response of chorda tympani nerve to taste stimuli in rats with conditioned taste aversion to saltiness / 中国应用生理学杂志

OBJECTIVE@#To explore the characteristic changes of the peripheral chorda tympanic nerve (CT) electrophysiological responses to salty stimulus and other taste stimuli in rats with the conditioned taste aversion to saltiness.@*METHODS@#Fourteen adult SD male rats were divided into a conditioned taste aversion to salty group (CTA) and a control group (Ctrl) (n=7/group). On the first day of the experiment, rats were given a 0.1 mol/L NaCl intake for 30 min, then, the rats in CTA and Ctrl groups were injected intraperitoneally with 2 ml of 0.15 mol/L LiCl and the same amount of saline respectively. On day 2, 3 and 4, the 30 min consumption of NaCl and distilled water was measured for both groups of rats. On the 4th day after the behavioral test of that day, CT electrophysiological recording experiments were performed on CTA rats and control rats.@*RESULTS@#Compared with the rats in Ctrl group, the electrophysiological characteristics of CT in CTA group rats did not change significantly the responses to the series of NaCl and other four basic taste stimuli (P＞0.05). The amiloride, the epithelial sodium channel blocker, strongly inhibited the response of CT to NaCl in CTA and Ctrl group rats (P＜0.01).@*CONCLUSION@#The electrophysiological responses of CT to various gustatory stimuli do not significantly change in rats after the establishment of conditional taste aversion to the saltiness.

A Case of Schwannoma of the Chorda Tympani Nerve / 대한이비인후과학회지

Schwannoma is a benign nerve sheath tumor composed of schwann cells. Most schwannoma arising in the middle ear are facial nerve schwannoma. In very rare occasions, schwannoma of the middle ear can arise from chorda tympani nerve. Hearing loss and tinnitus are the most common symptoms of patients with schwannoma of chorda tympani nerve and it can be treated by surgical excision. Recently, we treated a male patient with schwannoma of the chorda tympani nerve. This is the first case of schwannoma of the chorda tympani nerve reported in Korea. Herein, we present the case in detail with a review of the related literature.

Cochlear Implantation Using the Endomeatal Approach in a Child with a Extremely Hypoplastic Mastoid / 대한이비인후과학회지

The classic surgical technique for cochlear implantation was first introduced by House in 1961. This technique includes a mastoidectomy and a posterior tympanotomy, which has been most widely used for cochlear implantation. However, this approach may result in the injury of the chorda tympani nerve or the facial nerve. To avoid the risk of the neural injury, several alternative surgical methods have been developed. The endomeatal approach is one of the several alternative techniques. We present, along with a review of literatures, a case of cochlear implantation using the endomeatal approach performed in a child with an extremely hypoplastic mastoid.

Progress in the effects of injury and regeneration of gustatory nerves on the taste functions in animals / 生理学报

The sensor of the taste is the taste bud. The signals originated from the taste buds are transmitted to the central nervous system through the gustatory taste nerves. The chorda tympani nerve (innervating the taste buds of the anterior tongue) and glossopharyngeal nerve (innervating the taste buds of the posterior tongue) are the two primary gustatory nerves. The injuries of gustatory nerves cause their innervating taste buds atrophy, degenerate and disappear. The related taste function is also impaired. The impaired taste function can be restored after the gustatory nerves regeneration. The rat model of cross-regeneration of gustatory nerves is an important platform for research in the plasticity of the central nervous system. The animal behavioral responses and the electrophysiological properties of the gustatory nerves have changed a lot after the cross-regeneration of the gustatory nerves. The effects of the injury, regeneration and cross-regeneration of the gustatory nerves on the taste function in the animals will be discussed in this review. The prospective studies on the animal model of cross-regeneration of gustatory nerves are also discussed in this review. The study on the injury, regeneration and cross-regeneration of the gustatory nerves not only benefits the understanding of mechanism for neural plasticity in gustatory nervous system, but also will provide theoretical basis and new ideas for seeking methods and techniques to cure dysgeusia.

The effect of hyalinized chorda tympani nerve canal in protection of mastoid segment of facial nerve in middle ear surgery / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To investigate the effect of hyalinized chorda tympani nerve canal in mastoid segment to landmark facial nerve in middle ear surgery by means of observing the location relationship between hyalinized chorda tympani nerve canal and facial nerve.@*METHOD@#118 cases of cholesteatoma otitis media in our hospital undergoing tympanoplasty from 2008 to 2011 were retrospectively analyzed. In all the cases, the position of horizontal semicircular and fossa incus as well as the hyalinized chorda tympani nerve canal were used for landmark the height of facial ridge and vertical segment of facial nerve.@*RESULT@#The chorda tympani nerve of 99 patients were higher than the vertical segment of the facial nerve which were not exposed, and the vertical segment of the facial nerve in 9 patients, which were exposed, were 1-2 mm lower and 2-3 mm ahead or backward than the chorda tympani nerve. The horizontal semicircular and fossa incus were broken in 9 patients, of whom the vertical segments of the facial nerve were 1-2 mm lower and 2-3 mm ahead or backward than the chorda tympani nerve. The chorda tympani nerve of 1 patient were lower than the exposed vertical segment of facial nerve.@*CONCLUSION@#The hyalinized chorda tympani nerve canal in mastoid segment can landmark the positon of facial ridge, and it would be the complement to the traditional method of landmarking vertical segment of facial nerve, especially for those whose horizontal semicircular canal and fossa incus had been broken.

A Case of Image-Guided Posterior Tympanotomy in Chronic Otitis Media / 대한이비인후과학회지

Posterior tympanotomy is a procedure performed to access the posterior mesotympanum through a mastoid exposure while preserving the posterior external auditory canal wall. It is dangereous to drill the the site of procedure, as it is surrounded by incuidal fossa superiorly, facial nerve posteriomedially, and chorda tympani nerve anterolaterally, and forms a very narrow pathway. There is always a risk of surgical trauma involving important surgical structures, especially facial nerve and chorda tympani nerve. The development of image-guided surgery (IGS) has significantly improved the performance of many surgical procedures by aiding the identification of surgical landmarks, improving surgical outcomes, rendering the procedure safer and more efficient, especially for beginner otologic surgery, in revision operations, in cases of massive bleeding and tumor of complex anatomy. To see how IGS could help otologic surgeons to identify fine, important structures during posterior tympanotomy, we report a case of posterior tympanotomy in chronic otitis media, which was done using the image-guided surgical technique.

Timing of Sequential Bilateral Mastoidectomy and Functional Recovery with Respect to Taste / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: After bilateral mastoidectomy, taste change is common because of injury to chorda tympani nerve. We aimed to understand about the appropriate interval of sequential bilateral mastoidectomy. SUBJECTS AND METHOD: Retrospective review was carried out for 25 patients who underwent sequential bilateral mastoidectomy from March 2004 to November 2011. RESULTS: Among the 25 patients, there were 19 patients whose chorda tympani nerve was injured after bilateral mastoidectomy, and eight of those 19 patients complained of taste disturbance. The rates of dysfunction according to operation interval were within 6 month (55%, 5/9), between 6 and 12 months (33%, 2/6), and above 12 months (10%, 1/10). Compared to canal wall up mastoidectomy, for canal wall down mastoidectomy, taste disturbance was more common (p=0.001). CONCLUSION: The result supports that at least 6 months interoperative period for bilateral chronic otitis media may be needed to avoid taste disturbance. A further large study may validate this result.

Canal-wall-down mastoidectomy and tympanoplasty surgery preserving chorda tympani nerve integrality / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To report the way for searching the chorda tympani nerve and the significance for preserving the chorda tympani nerve during canal-wall-down mastoidectomy and tympanoplasty surgery.@*METHOD@#Sixty-six cases with chronic suppurative otitis media underwent canal-wall-down mastoidectomy and tympanoplasty surgery. According to the marker of the short crus of incus, the posterior wall of auditory canal was lowered and crista of the chorda tympani nerve was found through tracing the facial nerve contour. The chorda tympani nerve was preserved after clearing the surrounding tissue.@*RESULT@#Among the 66 cases, 24 cases had middle ear cholesteatoma, 42 cases had granulation in middle ear. The cholesteatoma and granulation on the surface of the chorda tympani nerve were cleared thoroughly. No neurotmesis or obvious change of taste occurred after operation.@*CONCLUSION@#Canal-wall-down mastoidectomy and tympanoplasty surgery preserving chorda tympani nerve integrality may preserve the structure and function of the chorda tympani nerve, reduce the risk of ossicle extrusion above the head of stapes and serve as a frame for transplanting fascia.

Applied anatomy of facial recess and posterior tympanum related to cochlear implantation / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To investigate the related parameters of temporal bone structure in the surgery of cochlear implantation through facial recess approach so as to offer a theoretical reference for the avoidance of facial nerve injury and the accurate localization.@*METHOD@#In a surgical simulation experiment, twenty human temporal bones were studied. The correlation parameters were measured under surgical microscope.@*RESULT@#Distance between suprameatal spine and short process of incus was (12.44 +/- 0.51) mm. Width from crotch of chorda tympani nerve to stylomastoid foramen was (2.67 +/- 0.51) mm. Distance between short process of incus and crotch of chorda tympani nerve was (15.22 +/- 0.83) mm. The location of maximal width of the facial recess into short process of incus, crotch of chorda tympani nerve were (6.28 +/- 0.41) mm, (9.81 +/- 0.71) mm, respectively. The maximal width of the facial recess was (2.73 +/- 0.20) mm. The value at level of stapes and round window were (2.48 +/- 0.20 mm) and (2.24 +/- 0.18) mm, respectively. Distance between pyramidalis eminence and anterior round window was (2.22 +/- 0.21) mm. Width from stapes to underneath round window was (2.16 +/- 0.14) mm.@*CONCLUSION@#These parameters provide a reference value to determine the position of cochlear inserting the electrode array into the scale tympani and opening facial recess firstly to avoid potential damage to facial nerve in surgery.

c-Fos Expression in the Nucleus of the Solitary Tract in Response to Salt Stimulation in Rats

Salt signals in tongue are relayed to the nucleus of the solitary tract (NST). This signaling is very important to determine whether to swallow salt-related nutrition or not and suggests some implications in discrimination of salt concentration. Salt concentration-dependent electrical responses in the chorda tympani and the NST were well reported. But salt concentration-dependency and spatial distribution of c-Fos in the NST were not well established. In the present study, NaCl signaling in the NST was studied in urethane-anesthetized rats. The c-Fos immunoreactivity in the six different NST areas along the rostral-caudal axis and six subregions in each of bilateral NST were compared between applications of distilled water and different concentrations of NaCl to the tongue of experimental animals. From this study, salt stimulation with high concentration (1.0 M NaCl) induced significantly higher c-Fos expression in intermediate NST and dorsal-medial and dorsal-middle subregions of the NST compared to distilled water stimulation. The result represents the specific spatial distribution of salt taste perception in the NST.

Trastornos del gusto posestapedostomías / Post stapedectomy taste disorders

Introducción: En su trayecto por el oído medio el nervio cuerda del tímpano (CT), se ve expuesto a lesiones quirúrgicas. Los trastornos del gusto se presentan como posibles secuelas del daño sobre la CT, lo cual puede afectar la calidad de vida de los pacientes. En las estapedostomías, la CT debe ser movilizada frecuentemente, y a veces seccionada para accederá la platina del estribo. Objetivo: Evaluar la evolución temporal de los trastornos del gusto posestapedostomías y su correlación con la preservación de la CT. Material y método: Estudio retrospectivo entre los años 2002 y 2007. Se analizaron las fichas clínicas y protocolos operatorios en busca de preservación o sección de la CT durante la cirugía. Se aplicó un mini cuestionario para evaluar la función gustativa y su evolución en el tiempo. Resultados: La CT fue preservada en 131 pacientes (93 por ciento) y seccionada en 10 pacientes (7 por ciento). La incidencia de alteraciones del gusto fue 7,6 por ciento> (10 pacientes) en el grupo con preservación de la CT y 20 por ciento> (2 pacientes) en el grupo que se seccionó (p >0,05). Todos los pacientes tuvieron una recuperación completa en su función gustativa antes de 12 meses luego de la cirugía, siendo más rápida en el grupo con preservación que en el que se seccionó la CT(5 meses versus 11 meses respectivamente). Conclusiones: Las alteraciones del gusto están presentes en pacientes sometidos a estapedostomías incluso cuando la CT es preservada. Cuando es seccionada no siempre se presentan trastornos del gusto, pero cuando están son más severos y duraderos.

Introduction: In its course through middle ear, the chorda tympani nerve (CTN) is potentially exposed to surgical injury. Possible sequels of CTN injury are taste disorders, which can affect the life quality of patients. During stepedectomies, the CTN often must be displaced or even severed in order to gain access to the stapes footplate. Aim: To assess the temporal evolution of post stepedectomy taste disorders and their correlation with CTN preservation. Material and Method: A retrospective study was conducted between 2002 and 2007. Medical records of 141 patients subjected to stapedectomy were analyzed in search for CTN preservation or section during surgery. A questionnaire was applied to evaluate postoperative taste function and its evolution over time. Results: CTN was preserved in 131 patients (93 percent) and sectioned in 10 patients (7 percent). The incidence of taste disorders was 7.6 percent (10 patients) in the CTN preserved group and 20 percent> (2 patients) in the CTN severed group (p>0.05). All patients had fully recovered taste function by 12 months after surgery, recovery being faster in the CTN preserved group than in the CTN severed group (5 months vs. 11 months respectively). Conclusions: Taste disorders may be present in patients subjected to stapedectomy even when CTN is preserved; taste disorders are more severe and long lasting in cases where the CTN is sectioned.

A Case of the Schwanomma Originated in the Middle Ear Cavity / 대한이비인후과학회지

Schwannoma is benign tumor that is originated from the schwann cell. It rarely occurs in the middle ear. Schwannomas of the middle ear may originate from the nerves of the middle ear cavity or by extensions from its neighboring structures. Most schwannomas arising from the middle ear are facial nerve schwannomas. We present a case of a 16-year-old male patient with primary middle ear schwannoma believed to arise from Jacobson's nerves. The tumor was easily dissected from the facial nerve and the chorda tympani nerve. The mass was successfully removed by canal down mastoidectomy, while preserving the hearing and facial nerve functions of the patient.

Taste Change after Middle Ear Surgery / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: During middle ear surgery, surgeons manipulate the chorda tympani nerve (CTN) at various degrees and warn the post-operative taste changes to patients preoperatively. The purpose of this study is to assess how many patients suffer from taste disturbance after surgery and the characteristics of their disease factors and surgical factors in patients complaining of it. In addition, it was designed to evaluate the clinical availability of electrogustometry (EGM)compared with subjective taste symptoms. SUBJECTS AND METHOD: One hundred thirty-one patients underwent middle ear surgery. Patients were divided to three groups, only tympanoplasty, tympano-ossiculoplasty without mastoidectomy and tympanoplasty with mastoidectomy. They were analysed by operative findings of CTN preserved, stretched, cut. The CTN function was measured at one day before surgery and one month after surgery by EGM. Taste questionnaires were given to all patients before and after surgery for one year. The results of EGM and questionnaires were compared with each other. RESULTS: In pre-operative EGM results of unilateral surgery, the lesion side of tongue had more elevated threshold of EGM than the contralateral side. In the post-operative EGM, any statistical factor was not significant and EGM results was not correlated with subjective symptoms. The results of the test questionnaraires was that thirty-three patients (25%) reported taste change. In tympanoplasty-preserved CTN group, more patients suffered from taste change than mastoidedctomy-cut CTN group. Symptoms were decreased taste sensation, dysgeusia, and decreased general sensation of tongue. Subjective recovery time was on the average of 2.7 months (two weeks to one year) after surgery. CONCLUSION: EGM was not correlated with subjective symptoms after surgery. Iatrogenic CTN injury in advanced middle ear infection may not cause taste disturbance. Surgeons should have efforts to preserve CTN in even mild middle ear diseases.

Applied anatomy of operation through posterior tympanum approach / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To provide the anatomic data for operation on the middle ear through the observation and measurement of related anatomic structure.@*METHOD@#Forty human temporal bones of 20 voluntary bone donors were dissected, relative anatomical data of operation were observed and measured under operating microscope through posterior tympanum approach entering posterior tympanum.@*RESULT@#The average distances from suprameatal spine to short crus of incus, pyramid segment of facial canal were 19.14 mm, 16.30 mm, respectively. The average distances from pyramid segment of facial canal to the surface of mastoid, crotch of chorda tympani nerve, posterior wall of auditory meatus were 20.84 mm, 11.28 mm, 4.40 mm, respectively. The average length of facial nerve in the horizontal segment, the perpendicular paragraph was about 11.60 mm, 15.30 mm, respectively. The average distance from pyramidal eminence to the anterior lip of round window niche, from oval window to round window niche, from incudostapedial joint to round window niche was 4.46 mm, 3.74 mm, 3.80 mm, respectively. The included angle of facial nerve in the horizontal segment and chorda tympani nerve with facial nerve in the perpendicular paragraph was 110.4 degrees, 24.8 degrees, respectively. Horizontal semicircular canal and facial nerve in the level paragraph was 17.5 degrees, long process of incus and incus buttress was 46.0 degrees.@*CONCLUSION@#The position of anatomic structure in middle ear was constant and the relationship including distance and angle between anatomic structures changed in limited region. The anatomical parameters provide a reference value for avoiding the injury during the operation.

Surgical approaches and related microsurgical anatomy about suprameatal approach: new surgical approach for cochlear implantation / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To study a new surgical approach for cochlear implantation.@*METHOD@#We operated on 8 cadaver heads (16 side) use Suprameatal approach for cochlear implantation, describe related anatomic mark.@*RESULT@#The electrode is passed through the suprameatal tunnel, the EAC groove, the space underneath the chorda tympani between the malleal and the long process of the incus, and the cochleostomy. Angle between tunnel and temporal imaginary line is 28.0 degrees +/- 1.3 degrees in adult, 29.0 degrees +/- 1.7 degrees in children, the location of inserting electrode into cochleostomy is (1.31 +/- 0.13) mm to round window in adult, (1.19 +/- 0.12) mm in child.@*CONCLUSION@#The SMA approach is a safe technique, maintaining a safe distance to facial nerve and chorda tympani. So We should make right decision in clinic.

Effect of preganglionic parasympathetic denervation on Nitric Oxide synthase in submandibular gland of adult albino rat

Adult albino rats were subjected to chorda tympani neurectomy on the right side and the left side served as the control. After different survival periods, the control and experimental submandibular glands were discected out and processed for histological and histochemical examinations. Chorda tympani neurectomy resulted in atrophic changes in about 90% of both seromucous acini and granular convoluted tubules of the submandibular gland. They showed statistically significant reduction in their mean diameters after denevation. The reduction in the diameter of the acini was more marked than that of the tubules. The atrophic acini became separated by wide spaces and their cells showed cytoplasmic vacuolation two weeks after chorda tympani neurectomy. At the third and the fourth weeks, an insignificant increase in the diameter was noticed in the tubules and acini. The interlobular striated ducts showed cytoplasmic vacuolation two weeks after denervation which became more prominent during the third and fourth week after chorda tympani neurectomy. After denervation, NADPH-d positive nerve terminals were absent around the majority of acini and the granular convoluted tubules and were seen around the remaining 7-10% of the acini and 10-23% of the tubules. Throughout the period of denervation, NADPH-d positive nerve terminals were found around the striated ducts, the interlobular ducts and the blood vessels. The majority of the NADPH-d positive nerve terminals around the acini and granular convoluted tubules are parasympathetic in origin derived from the chorda tympani. The origin of NADPH-d positive nerve fibers around some acini and granular convoluted tubules and in relation to the remaining duct system and blood vessels needs further investigation

Postoperative Results of Canal Wall Up Mastoidectomy Only Performing Anterior Tympanotomy / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Retrospective reflect of canal wall up (CWU) mastoidectomy with posterior tympanotomy revealed some problems such as ineffectiveness against the recurrence of cholesteatoma, reclosure of ventilation route and that a posterior tympanotomy might be harmful to inner ear. Objectives of this study is to evaluate the effect of mastoidectomy with anterior tympanotomy on postoperative hearing results and complications. SUBJECTS AND METHOD: From January 1998 through July 2001, 29 cases of CWU mastoidectomy with anterior tympanotomy were reviewed retrospectively. All of the cases were difficult to perform posterior tympanotomy due to anatomical variations and had lesions restricted to anterior epitympanum. The hearing results were assessed by postoperative 1-year pure tone average and postoperative 1-year air-bone gap (ABG), and we checked complications. RESULTS: Of the 29 cases, 21 cases (72.4%) had ABG <20 dB in the postoperative 1-year, with the postoperative 1-year ABG of 14.9+/-9.2 dB. The postoperative hearing gain was 10.1+/-10.6 dB. There were 3 cases of chorda tympani nerve cutting, 1 case of accidental malleoincudal joint dislocation and 1 case of recurrence. CONCLUSION: Anterior tympanotomy could be a good approach for ventilation in selected CWU mastoidectomy approach, and further long term follow-up is needed to study about recurrence.