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.

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.

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.

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.

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.

Topographic Anatomy of the Discomalleolar and Anterior Malleolar Ligaments in Human Adults and Fetuses / 체질인류학회지

During temporomandibular joint (TMJ) formation, discomalleolar ligament (DML) and anterior malleolar ligament (AML) are formed within the dorsal end of the 1st branchial arch. But, DML is known as a remnant or the degenerated tissue through the TMJ development. There is few reports said that damage of AML and DML cause the damage of middle ear during surgical procedures. Especially, in case of anterior disk displacement of TMJ, aural symptom can be made via DML due to hyperextension anteriorly. A few studies have been reported about DML and AML in embryological and histological points of view, morphology and clinical aspects of DML and AML are still unclear. Four fetuses and sixteen adult hemi -sectioned heads were dissected to clarify the topographical relationship of AML and DML and to find out the anatomico -clinical relevance related with temporomandibular disorder. In fetal specimens, DML was firmly attached from the disk of the TMJ to the malleus. Also, AML in which distinguished into the superior and inferior lamellae was running anteriorly and continuous with the sphenomandibular ligament (SML) through the future petrotympanic fissure (PTF). DML attached to the malleus was observed in all adult specimens and was expanded broadly to the disk and capsule of the TMJ as shown the V -shaped ligament structures. The average distance between the anterior aspects of the malleolar head to the anterior wall of the tympanic cavity was 1.13 mm(0.75 ~1.59), and the length of the DML from the anterior aspect of the malleolar head to the attached site to the TMJ capsule at the PTF was 5.37 mm (4.53 ~6.07). The average width of the DML at the PTF was 6.06 mm (4.72 ~7.46). Most of the posterior attachments of the DML were the cases in which DML was directly attached to the malleus (68.7%). In all specimens, DML was attached to the disk and capsule of TMJ and attached to the anteromedial border of the PTF concurrently. In this study, two morphological patterns of AML were observed according to the presence of the bony ridge on the Huguiers canal in the PTF. The bony ridge of the Huguiers canal showed DML and AML separately in 56.3%, and the fused pattern of DML and AML was observed in 43.7%. AML was not distinguished with two lamellae in most specimens, superior ligament fibers were attached to the anteromedial border of the PTF and most of the inferior lamella was entering the gap in PTF and continuous with the SML. Average length from the anterior aspect of the malleolar head to the exit point of the AML on the PTF was 8.40 mm(6.62 ~11.42), and the shortest distance between the AML and chorda tympani was 2.01 mm(1.25 ~3.02). Taken all together, DML and AML were not the rudimentary, but the distinguishable structures in adults. Through the various morphological findings, DML and AML were separated ligamentous structures in which might be given rise from the divergent origin. And the anterior hyperextension of the disk of TMJ did not lead the movement of the malleus in the tympanic cavity, whereas, the movement of the malleus followed by the traction of the AML and SML was observed in a few cases. So, this results can be explained the possibility of the clinical symptom on the middle ear in case of the over -traction of the AML and SML.

Morphology and topography of the lingual nerve in Koreans

Two major salivary glands, submandibular duct, lingual nerve, and vessels are situated beneath the mouth floor. Among these, passing through the pterygomandibular space, lingual nerve is innervated to the lingual gingiva and the mucosa of mouth floor, and is responsible for the general sensation of the anterior two thirds of the tongue. So, the injury of the lingual nerve during an anesthesia or surgery in the retromolar area may cause complications such as a numbness, a loss of taste of the tongue and the other dysfunctions. Therefore, to find out the morphology and the course of lingual nerve and to clarify the topographical relationships of lingual nerve at the infratemporal fossa and paralingual space area, 32 Korean hemi-sectioned heads were dissected macroscopically and microscopically with a viewpoint of clinical aspect in this study. This study demonstrated various anatomical characteristics with relation to the course and topography of the lingual nerve in Koreans. And clinical significances based on the anatomical variations through the topography of the courses and communications between the mandibular nerve branches were described in details.