Hiroshi Aritomo

Measurement of the Ossicular Vibration Ratio in Human Temporal Bones by Use of a Video Measuring System

Vibration modes of the ossicles and the lever function were studied in human cadaver temporal bones with an intact cochlea. After placing tiny steel spheres on the ossicles, ossicular vibration to a sound stimulus was measured by observing the displacements of the spheres under a microscope with strobe illumination by means of a video measuring system. The lever ratio varied from 1.9 at 0.6 kHz (minimum) to a peak of 6 near 2 kHz. This relatively high lever ratio at higher frequencies was considered to be caused by a shift of the malleus-incus rotation axis secondary to the loading of the cochlear fluid on the ossicular system. Dependence of the lever ratio on frequency indicated that the rotation axis of the ossicles was not fixed, but variable according to frequency due to a relative increase in the translational movements of the rotation axis of the malleus and incus with frequency.

Effect of Changes in Mass on Middle Ear Function

Vibrating systems such as the middle ear are affected by changes in mass. After disease or ear surgery, significant changes in mass may contribute positively or negatively to the postoperative hearing threshold. This article describes experiments in 15 human temporal bones of the addition or reduction of mass on the middle ear transfer function. Measurement of stapes and umbo vibration was performed using a Laser Doppler Vibrometer before and after the addition of different masses at several sites on the tympanic membrane (TM) and ossicular chain. The input was 61 pure tones swept from 147 to 19433 Hz at 80 dB SPL. The addition of mass onto the TM produced varying detrimental effects on sound transmission, depending on the location and amount of mass. The insertion of ventilation tubes, weighing 12 to 17 mg each, produced losses at 1.5 to 5.0 kHz compared with tympanotomy alone. Addition of mass to the umbo and malleus head produced a loss at mid and high frequencies, whereas addition of mass on the incus long process and stapes also produced a high-frequency decrease in stapes displacement. Reduction of TM mass by removal of the epithelium produced an increase, especially at 2.0 to 4.0 kHz.

The Role of Pars Flaccida in Human Middle Ear Sound Transmission

The role of the pars flaccida in middle ear sound transmission was studied with the use of twelve otoscopically normal, fresh, human temporal bones. Peak-to-peak umbo displacement in response to a constant sound pressure level at the tympanic membrane was measured with a noncontacting video measuring system capable of repeatable measurements down to 0.2 micron. Measurements were made before and after pars flaccida modifications at 18 frequencies between 100 and 4000 Hz. Four pars flaccida modifications were studied: (1) acoustic insulation of the pars flaccida to the ear canal with a silicone rubber baffle, (2) stiffening the pars flaccida with cyanoacrylate cement, (3) decreasing the tension of the pars flaccida with a nonperforating incision, and (4) perforation of the pars flaccida. All of the modifications (except the perforation) had a minimal effect on umbo displacement; this seems to imply that the pars flaccida has a minor acoustic role in human beings.

Comments on ‘‘Acoustic transfer characteristics in human middle ears studied by a SQUID magnetometer method’’ [J. Acoust. Soc. Am. 82, 1646–1654 (1987)]

The study by Brenkman et al. [J. Acoust. Soc. Am. 82, 1646-1654 (1987)] of malleus umbo and anterior crus of stapes displacement in 14 human temporal bones shows a mean -7.3-dB/oct slope above 1.0 kHz for stapes displacement in response to a 80-dB SPL input at the eardrum. The slope they obtained for midfrequency (1.0-4.0 kHz) stapes displacement is significantly flatter than what was found previously [Gyo et al., Acta Otolaryngol. 103, 87-95 (1987); Gundersen, Prostheses in the Ossicular Chain (University Park, Baltimore, MD, 1971); Kringlebotn and Gundersen, J. Acoust. Soc. Am. 77, 159-164 (1985); Vlaming and Feenstra, Clin. Otolaryngol. 11, 353-363 (1986a)]; in these studies, stapes displacement rolled off at -12.0 to -14.9 dB/oct above 1.0 kHz. It appears that their mean midfrequency stapes displacement slope has been flattened by some unusual results in a small number of ears. Possible reasons for these results are discussed.

Width of the normal facial canal measured by high-resolution cone-beam computed tomography

Abstract Conclusions: In the facial canal, discrepancies between left and right side measurements at each point may be useful in the assessment and diagnosis of facial canal-related pathologies. Objectives: This study was performed to obtain accurate and high-resolution images of the normal facial canal and measure its widths on cross-sections of the canal at anatomically and clinically important sites using high-resolution cone-beam computed tomography (CBCT). Methods: CBCT volume data of bilateral temporal bones were obtained from 28 healthy adult volunteers. The widths of the bony facial canals were measured at the meatal foramen, the cochleariform process, the stapes, the pyramidal eminence, and the point of emergence of the chorda tympani in the vertical segment. Results: The widths of the facial canal at each point were similar bilaterally (r = 0.54–0.85, p < 0.01), but showed regional differences and site-specific variations. The narrowest of the five sites was the level of the meatal foramen (p < 0.05), as reported previously. The second narrowest site was the level of the stapes (p < 0.01) followed in order by the level of the cochleariform process, the pyramidal eminence, and the point of emergence of the chorda tympanis (p < 0.01).

Bilateral Gradenigo's Syndrome; A Case Report.

Gradenigos syndrome was diagnosed in a 5-year-old male with bilateral acute otitis media, paralysis of both abducens nerves and bilateral irritation of the trigeminal nerves. After myringotomy and administration of antibiotics, his tympanic membrance became normal, and the bilateral trigeminal nerve irritation disappeared, but residual mastoiditis was revealed by X-ray examination. Right extended mastoidectomy was performed including removal of the bony sinus plate on Mar. 2, 1990. Although bilateral abducens palsy improved immediately, serological findings and double vision deteriorated again 10 days after the operation. Reexploration was done on Mar. 16, 1990. Residual inflammatory changes in the petrous apex were eradicated, especially around the lateral sinus and anterior to the superior semicircular canal through the petrous apex. An extradural abscess was found at the petrous apex. The left trigeminal nerve irritation and the left abducens paralysis was attributed to the right petrositis because bilateral abducens nerve function recovered completely after the second operation on the right temporal bone. Since extradural abscess at the petrous apex is difficult to diagnose preoperatively and has been reported in many patients with Gradenigos syndrome, it must be kept in mind in the diagnosis and the treatment of Gradenigos syndrome. Twelve cases of Gradenigos syndrome reported in Japan from 1960 to 1992 were reviewed. Acute otitis media was the cause in five, all children. In three of them abducens paralysis appeared within one week after onset of the acute otitis media. Mortality of Gradenigos syndrome is still 10%, similar to that of brain abscess associated with otitis media.

Olfactory Neuroblastoma; A Case Report.

A 49-year-old female consulted our clinic with a complaint of righ trecurrent epistaxis on December 2, 1989. A tumor was found in the right nasal cavity. Radiographic study failed to disclose the extent of the tumor, because of associated paranasal sinusitis. MRI (magnetic resonance imaging) studies suggested that the tumor was limited to the right nasal cavity. Right lateral rhinotomy was performed and the tumor was totally removed on December 27, 1989. The tumor was confirmed to be neurogenic by the findings of intracytoplasmic neurosecretory granules and neuritic processes in the tumor cells examined by electron microscopy. It was diagnosed as olfactory neuroblastoma because of its location and the normal value of urine VMA (vanillyl mandelic acid). There was no evidencel of recurrence during 18 months of follow up. The authors confirmed the usefulness of MRI in the evaluation of the extent of the tumor and the necessity of electron microscopy to diagnose olfactory neuroblastoma.

Treatment of Tinnitus with Tizanidine Hydrochloride.

The clinical effects of tizanidine hydrochloride were evaluated in 58 patients with tinnitus. The subjective improvement rate was 60.0%. A better effect was obtained when the loudness of the tinnitus was more than 10 dB and when treatment was continued for over 4 weeks. Treatment with tizanidine hydrochloride alone was as effective as combined treatment with other drugs.Shoulder stiffness improved in 47.5% of the patients and in these patients tinnitus responded better. Side effects were observed in 15.5%, but none were serious.