Hiramori Sakamoto

Strial Circulation Impairment due to Acoustic Trauma

Blood circulation in the cochlear lateral wall after exposure to a non-physiological level of sound (120-125 dB SPL, 3 h) was investigated immunohistologically. Kanamycin (KM), which was expected to function as a tracer of blood flow, was administered to guinea pigs 5 min to 21 h after sound termination. At 5-30 min, KM was scarce in the capillaries of the stria vascularis (CSVs), whereas abundant KM was present in the spiral ligament vessels. These findings differed markedly from those in non-sound-exposed animals. After the initial period, KM gradually did enter into the CSVs, but its pattern of existence there differed from the normal pattern. These observations suggest that acoustic trauma causes blood stagnation in the strial capillaries, leading to strial dysfunction.

Blockage of reuniting duct in Meniere's disease

Conclusion: The bony saccular orifice to the bony groove of the ductus reuniens (reuniting duct) could not be visualized in the Menieres ear with significantly greater frequency compared with normal subjects, which suggests that the reuniting duct is affected by radio-opaque substances in CT findings. Objective: This study investigated a more specific, objective, and simpler strategy to diagnose Menieres disease by assessing the reuniting duct. Subjects and methods: We examined the ears of 12 patients with definitely diagnosed unilateral Menieres disease in stage 3 based on Menieres disease criteria proposed by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), and the ears of 12 normal control subjects using three-dimensional (3D) cone beam CT. Results: The bony groove of the reuniting duct between the saccule and cochlea was visualized in all control subjects. However, the bony saccular orifice to the bony groove could not be visualized in the lesional ear of Menieres patients with significantly greater frequency compared with those of the contralateral non-lesional ears and control ears (p < 0.01). This orifice was not patent in 66.7% (8 of 12 ears) on the lesional side but all contralateral non-lesional ears of the patients and normal control ears were patent.

Assessment of Meniere's disease from a radiological aspect – saccular otoconia as a cause of Meniere's disease?

Abstract Conclusion: Significant reduced visualization of the reuniting duct (ductus reuniens; RD), saccular duct (SD) and endolymphatic sinus (ES) in Menieres disease (MD) compared with normal control ears on three-dimensional (3D) CT imaging suggests the blockage of endolymphatic flow there with radiodense substances, which may be explained by dislodged otoconia from the saccule. These structures could be involved in the pathogenesis of MD. Objective: This study was designed to visualize and assess the RD, SD and ES in patients with MD using 3D CT. Methods: Sixty-two patients with a definite diagnose of unilateral MD, based on criteria proposed by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), were compared with contralateral ears and normal controls (26 ears) using 3D CT. The RD, SD and ES were scrutinized for patency on 3D CT images. Results: MD ears showed loss of continuity of the RD, SD and ES based on evaluation of 3D CT images, and differed significantly from normal healthy control ears (p < 0.01).

Visualization and assessment of saccular duct and endolymphatic sinus

Abstract Conclusion: The saccular duct and endolymphatic sinus run in the bony groove, before reaching the orifice of the vestibular aqueduct. We first clinically visualized this sulciform groove using three-dimensional (3D) cone beam CT images. This strategy can be useful to assess the condition of the saccular duct and endolymphatic sinus concerning the longitudinal flow system of endolymph. Objective: To assess the saccular duct and endolymphatic sinus in the endolymphatic system in order to advance clinical studies on inner ear dysfunction. Methods: The sulciform groove of the saccular duct and endolymphatic sinus of human subjects was analyzed by cone beam CT and compared with that of a cadaver. Results: We could obtain reconstructed 3D CT images of the sulciform groove of the saccular duct and endolymphatic sinus using several CT window levels.

Three-dimensional images of the reuniting duct using cone beam CT

Conclusion. There is a bony groove under the course of the reuniting duct of the inner ear. Cone beam CT could show three-dimensional (3D) reconstruction images of this groove in a cadaver and living human subjects. Objective. To obtain simple and universal images of the reuniting duct in humans for clinical use. Materials and methods. We investigated the reuniting duct macroscopically by observing the temporal bone in cadavers and living human subjects using cone beam CT. 3D reconstruction images of the duct were analyzed by the rendering software IVIEW. Results. The reuniting duct showed a bony groove between the saccule and cecum of the hook portion of the cochlea that could be three-dimensionally visualized by cone beam CT. A bony groove image in a living human subject could also be visualized by cone beam CT.

Assessment of the reuniting duct by three-dimensional CT rendering

Conclusion: The rendering strategy sometimes induces misunderstanding of the image. We demonstrated a more accurate image of the bony groove of the reuniting duct using three-dimensional (3D) cone beam CT image, which was less affected by artifacts created by the rendering effect. Objective: To obtain a suitable image of the groove of the reuniting duct for future morphological study. Materials and methods: The grooves of reuniting ducts in 10 healthy human subjects were analyzed by cone beam CT in comparison with a cadaver study. Results: We could obtain more accurate 3D CT images of the bony groove in human subjects by checking the landmarks of 3D CT images.

Cochlear strial blood circulation.

The present immunohistologic study demonstrates that cochlear strial blood circulation is markedly damaged in guinea pigs subjected to intense acoustic stimulation. In contrast, autonomic unbalance of the inner ear induced by resection or electric stimulation of the superior cervical ganglion has no appreciable effect on cochlear strial blood flow. In consequence, although strial blood circulation in the cochlea is susceptible to pathological change in some conditions, it does not appear to be affected by autonomic unbalance alone.

Probable Function of Boettcher Cells based on results of Morphological Study: Localization of Nitric Oxide Synthase

Boettcher cells lie on the basilar membrane beneath Claudius cells. The cells are considered supporting cells for the organ of Corti, and present only in the lower turn of the cochlea, which responds to high-frequency sound. Boettcher cells interdigitate with each other, and project microvilli into the intercellular space. Their structural specialization suggests that Boettcher cells may play a significant role in the function of the cochlea. Nitric oxide synthase (NOS) has previously been detected in substructures of the cochlea. In the cochlea, it is believed that nitric oxide plays an important role in neurotransmission, blood flow regulation, and induction of cytotoxicity under pathological conditions. Findings concerning detection of NOS on Boettcher cells are rare. We demonstrated here the localization of NOS on Boettcher cells of the rat by immunohistochemistry using polyclonal antibody to NOS. On observation with the light microscope using DAB staining, positive immunostaining to NOS was observed in Boettcher cells. In immunoelectron micrographs, NOS was detected abundantly in the cytoplasm of the interdigitations. This suggests that the interdigitations may play significant roles by using NOS. It follows from this that the nitric oxide (NO) on Boettcher cells may influences neighboring Boettcher cells. The ultrastructure of Boettcher cells suggests that they may be active cells, which perform both secretory and absorptive functions.

Electron Microscopic Observation of Communication between Inner Ear Stereocilia under Normal and Noise stimulated Conditions

The ultrastructure of communication between inner ear stereocilia under normal and noise stimulated conditions was studied in the guinea pig. With ruthenium red added to the pre- and post fixation solutions, the connections between the stereocilia could be observed in more detail than with ordinary fixation. After exposure to 1,000 Hz 110 dBSPL sound for 3 h, parts of the connections between the stereocilia had disappeared, and adherence between the adjoining stereocilia was observed. The results of our study lend support to the fact that the congregation of stereocilia after noise stimulation is due to the sticky adjoining stereocilia membrane.

Blockage pattern of longitudinal flow in Meniere's disease.

Abstract Conclusion: In the present study, classification of the patterns of 3D CT images of the ductus reuniens (reuniting duct) (RD), saccular duct (SD), and endolymphatic sinus (ES) gave more precise information for assessing the pathological condition of Menieres disease (MD) than our previous study. Objective: This study attempted to provide more detailed information on MD by classifying the patterns of 3D CT images of the RD, SD, and ES in patients with MD. Methods: We examined the ears of 62 patients with definitely diagnosed unilateral MD based on the criteria of the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) using 3D CT. The 3D CT images of bony grooves of RD, SD, and ES (BRD, BSD, and BES) were classified into patterns according to aspects of their patency. Results: BRD could be classified into six types by assessing their patency defined using the criteria in this study. In the ears on the affected side of patients with MD, the BRD, BSD, and BES lost continuity in 3D CT images along their bony routes and were significantly different from normal healthy ears (p < 0.01). There were no significant differences among each stage of MD in the distributions of BRD and BES except for BSD.