Mamoru Suzuki

Conclusion: Various changes were observed in the cupula, including shrinkage and enlarged volume, following the disruption of the membranous labyrinth. Cupular change after membranous labyrinth disruption may be a pathology of vestibular disorders. Objectives: To observe the morphological changes of the cupula after disruption of the membranous labyrinth and to compare the cupular changes with changes in the compound action potential (CAP) of the ampullary nerve. Methods: A labyrinthine injury model was created by puncturing the membranous labyrinth of bullfrogs. The cupula was observed from 3 to 17 days after the membrane puncture. The CAP in response to mechanical endolymphatic flow was recorded from the ampullary nerve. The correlation between cupular change and CAP positivity was evaluated using the authors' scale. Results: Various kinds of cupular changes including shrinkage were observed. Cupular change was more severe after a longer survival period. Large or elongated volume of the cupula was also observed, which was not observed in our previous study using gentamicin. The CAP could be recorded even when the cupular change was severe.

Conclusion. The outcome of surgery depends on complexities of middle ear anomalies and definite diagnosis can only be achieved during exploratory tympanotomy. We must be aware that the pathology of the congenital ossicular anomalies is variable and careful surgery is needed for hearing improvement. Objective. This study aimed to investigate congenital ossicular malformation. Subjects and methods. Fifteen cases of ossicular anomalies without external ear malformation were studied. The anomaly of the incus-stapes complex was the most frequent. There were two cases of fused incudostapedial (IS) joint, which is an extremely rare occurrence. Case 1 was a 33-year-old man, in whom otosclerosis was suspected and exploratory tympanotomy was performed. The IS joint was fused, and the stapes was immobile. Small fenestra stapedectomy was performed. In case 2, a 52-year-old woman, otosclerosis was also suspected and exploratory tympanotomy was performed. The IS joint was fused and the incus was fixed. After the long process of the incus was cut, the stapes became mobile. However, since the incus remained immobile, it was removed and was placed on the stapes. In both cases, the hearing improved after surgery. The averaged hearing gain of 15 cases was 28.8 dB.

Purpose: This study aimed to investigate the validity of adjusting computed tomography thresholds in order to replicate a temporal bone model suitable for dissection training and education.Materials and methods: A simulated three-dimensional model of a human temporal bone was prototyped using selective laser sintering. The powder layers were laser-fused, based on detailed computed tomography data, and accumulated to create a three-dimensional structure. The computed tomography threshold value of the stapes was modified on standard triangular language file in order to replicate the stapes. The intensity value was determined to select the fluid lumen of the inner ear and the bone surface, in order to replicate the inner ear.Results: The model could be shaved, using surgical instruments, in the same manner as during real surgery. The stapes could be reproduced, making this model even more realistic than a previous version. The inner ear was recreated, along with the surrounding bony wall and the ossicles.Conclusion: This model facilitates dissection training and easy understanding of the relation between the labyrinth and the surrounding structures.

Conclusion This 3D prototyped model constructed using a selective laser sintering method serves as a good material for surgical simulation of a malformed ear. Objective In order to perform surgery of the malformed ear, a thorough understanding of the anatomy of the ear is required, together with sufficient experience. The aim of this study was to investigate the validity of a prototyped temporal bone model for surgical simulation. Material and methods Simulated 3D models of two cases of congenital aural atresia were prototyped using a selective laser sintering method. Conventional surgical instruments were used to dissect the models. Results Abnormal structures of the middle ear, such as the ossicles, labyrinth and facial nerve, were identified by dissecting the model. Presurgical dissection informed the surgeon of the optimum orientation for surgery. The model was disinfected and could be handled by the surgeon in the operating room. Surgery could be carried out safely although in one case it was canceled because of the highly abnormal location of the middle ear cleft and facial nerve.

Objective The skills of ear surgery are best developed by dissecting a temporal bone. However, only a limited number of trainees can be afforded this opportunity because of the scarcity of available bones. The aim of this study was to investigate the validity of a prototype temporal bone model for surgical training and education. Material and Methods A simulated 3D model of a human temporal bone was made using a selective laser sintering method. The powder layers were laser-fused based on detailed CT data and accumulated to create a 3D structure. Conventional surgical instruments were used to dissect the model under a microscope. Results The model was as hard as real bone and surface structures were accurately reproduced. The model could be shaved using a surgical drill, burr and suction irrigator in the same way as a real bone. The malleus and incus were reproduced. The semicircular canals and the oval and round window niches were identified. Cavity structures, such as the semicircular canal, vestibule, antrum and air cells, were filled with powder which had to be removed using a pick and suction irrigator during dissection. A magnified model was useful for educating medical students. Conclusion This prototype 3D model made using selective laser sintering serves as a good educational tool for middle ear surgery.

The anatomy of the temporal bone is extremely complicated. If a three-dimensional model could be simulated, it would greatly contribute to the stereoscopic understanding of anatomy and surgery. A simulated three-dimensional model of a human temporal bone was prototyped using the selective laser sintering method. The model could be shaved using a surgical drill in the same way as in real surgery. A magnified model was particularly useful for the instruction of anatomy and surgery. When a translucent area was selected, a bony labyrinth could be created together with an internal auditory meatus and facial nerve, which also contributed to the easy understanding of the inner ear structure. The three-dimensional prototyped model using selective laser sintering serves as a good educational material for middle ear anatomy and surgery.

Physiology of the semicircular canal (sc) was studied by applying different manipulations to the isolated frog sc. Function of the cupula was investigated by mapping out the mechanical sensitivity on the cupular surface and by removing and replacing the cupula. The cupula was found to be most essential for effective activation of sc receptors. Responses of sc receptors to direct temperature change were studied. The sc nerve discharge increased and decreased due to cool and warm temperature change respectively. This suggests a possibility of direct temperature effect as one of the mechanisms of caloric response.

Benign paroxysmal positional vertigo (BPPV) is one of the common vestibular disorders. Canalolithiasis is thought to be a likely lesion. A canalith repositioning procedure (CRP by Epley) generally yields good resolution of vertigo and nystagmus. The authors confirmed the efficacy of this procedure on typical BPPV of the posterior semicircular canal type. We designed a new procedure for BPPV of the lateral canal type, which also yielded satisfactory results. BPPV sometimes presents a nystagmus pattern, which suggests multiple lesions. We have seen eight cases of BPPV showing nystagmus that combines both the posterior and the lateral canal types. Combined CRP was performed on these cases, which again gave good clinical results. Other BPPV cases were associated with central lesions. We must be aware that BPPV may involve multiple canals and may be associated with central lesions.