Taizo Takeda

Experimental Study on Meniere's Disease

Experimental hydrops caused by underabsorption of endolymphatic fluid is a model of remissional stage of Menieres disease. In this study, another type of model, ie, hydrops caused by overproduction of endolymphatic fluid, was accomplished by applying various pressures into scala media through a micropipette via stria vascularis. This type of hydrops could be a model of attacks of Menieres disease. By using two types of the model, effects of glycerol administration and of opening the endolymphatic sac were discussed.

Treatment of Ménière’s Disease with Isosorbide

The effects of isosorbide – a dehydric alcohol formed by the abstraction of two molecules of water from one of sorbitol – on Meniere’s disease were examined, first using a model and then clinically. (

Facial nerve to facial canal cross-sectional area ratio in children

The incidence of facial palsy among children is lower than that among adults, and the recovery rate after facial palsy among children is higher than that of adults. To investigate these differences, we compared the cross‐sectional area ratio of the facial nerve to that of the facial canal in 26 pediatric temporal bone specimens with that of 10 adult temporal bone specimens. The ratios were 0.31 ±0.08,0.35 ±0.10, and 0.18 ± 0.12, respectively, in the labyrinthine, horizontal, and mastoid segments of pediatric specimens. The ratios for adult specimens were 0.46 ±0.07, 0.52 ± 0.17, and 0.37 ± 0.04, respectively, in the labyrinthine, horizontal, and mastoid segments. These ratios were all significantly smaller than those for the corresponding segments of the adult specimens (P<.01). The results indicate that in children there is less possibility for entrapment of the facial nerve in the facial canal, and that children require facial nerve decompression less often than adults.

Pathogenesis of widened AP-SP complex in cases of cerebellopontine angle tumors

Pathogenesis of widened AP-SP complexes often noted in electrocochleograms (ECochGs) in cases of cerebellopontine angle tumors remains unclear. As acoustic neuromas usually originate from the vestibular nerve, some changes in this nerve might be involved in producing the broadened waveform. Effects of lidocaine on the AP-SP complex were investigated in guinea pigs by injecting this compound into the root exit zone of the vestibular nerve, where the cochlear efferent fibers run together. The AP-SP complex in response to clicks and tone bursts was recorded at the bony wall of the scala vestibuli in the basal turn of the cochlea. Inactivation of the efferent cochlear fibers resulted in a marked widening of the waveform, independent of the interstimulus intervals (ISIs). This broad wave was composed of a DC shift which was quite similar to the envelope curve of the acoustic stimuli. Although the effect of activity of the efferent cochlear fibers on negative summating potential (SP) has not been reported in detail, the authors concluded that the broad waveform observed in ECochGs in cases with cerebellopontine angle tumors was caused by enhanced negative SP due to inactivation of efferent cochlear fibers.

Antidromically evoked facial nerve responses in guinea pigs: a basis for clinical applications in patients with facial palsy.

SummaryWe investigated the differences in wave form in antidromically evoked facial nerve responses in guinea pigs with and without facial nerve dysfunction. The antidromic facial nerve responses were evoked with alternative stimulation of positive and negative square-wave pulses of 0.1 ms duration and recorded at the bony fallopian canal near the geniculate ganglion. One hundred responses were summed by a signal processor. The application of alternative stimulations made it possible to eliminate stimulus artifacts and to analyze precisely the waves with latencies shorter than 0.5 ms in the test animals. Normal antidromic facial nerve responses showed a triphasic wave form with two positive and one negative peaks. A blockade of the nerve between the recording and stimulating sites resulted in transformation of the wave into a monophasic one. A proximal blockade to the recording site changed the wave form to a biphasic shape. These findings suggest that the site of an intratemporal facial nerve lesion can be predicted from the wave forms evoked by antidromic facial nerve responses.

Interstitial fluid pressure in the facial nerve: Relationship between facial nerve pressure and cerebrospinal fluid pressure☆

The possibility of measuring interstitial pressure in the facial nerve using a servo-nulling system was investigated. As a pilot study, interstitial fluid pressure in the extirpated medulla oblongata was measured using this system, and was found to be proportional to the pressure applied to the surrounding tissue block. Interstitial fluid pressure of the facial nerve in guinea pigs was also measurable with this system. The pressure in the facial nerve fluctuated with respiration and/or heart beat, as did CSF pressure. Respiratory fluctuations in facial nerve and CSF pressures ceased when the respirator was stopped. Facial nerve pressure appeared to be closely related to CSF pressure; the injection of saline into the CSF space resulted in an increase in facial nerve pressure. Measurement of facial nerve pressure by a servo-nulling system should be useful in evaluating the pathogenesis underlying facial palsy.

An Animal Model of Ischemic Facial Palsy

We investigated facial palsy which was induced by the interruption of the petrosal artery in guinea pigs. Forty animals were observed for 2 months regarding their behavioral facial nerve function and assessed by the blink reflex. Morphological changes in the intratemporal portion were observed with transmission electron microscopy in 20 animals with an interrupted petrosal artery. Facial palsy developed in 85.0% within 3 days after the interruption. The degree of palsy varied from mild to severe. Remission of palsy required 2–3 months in severe cases, 3 weeks or less in mild/moderate cases. Histological studies revealed a striking difference in the degree of degenerative changes between severe cases and mild/moderate cases. Animals with severe palsy showed extensive axonal atrophy and myelin disruption from the early stage. Meanwhile, degenerative changes were slight in cases with mild/moderate palsy. Regenerating unmyelinated fibers appeared 1 week after the interruption, but diminished in number 4 weeks later. Thereafter, new myelin was reformed on fibers. In cases of severe nerve damage, however, this regeneration process did not always seem to work well. A decrease in number and an irregular shape of the fibers were noted in animals with incomplete recovery. This animal model may be helpful for understanding the pathophysiology of ischemic facial palsy.

Testing of otolith function.

In order to investigate otolith function, horizontal eye displacement in total darkness during tilting laterally about body axis was examined in 23 normal subjects and 29 patients with vestibular lesions. The mean and standard deviation of this eye displacement in normal subjects were 18.9 + 6.1 degrees at 15 degrees of body-tilt. Thus, eye displacement below the lower tolerance limit of normal eye displacement at 15 degrees of body-tilt, that is, 8.8 degrees, was judged to be abnormal. Meanwhile, 12 cases or 41.4% of 29 patients with vestibular lesions showed abnormal eye displacement in this test. Especially in cases with positional vertigo and/or dizziness, the occurrence of abnormal results in this test (69%) was far higher compared with that of cases where vertigo and/or dizziness was not associated with postural changing (19%). Therefore, these abnormal results seem to be closely related to the disorder of otolith system.

Antidromically evoked facial nerve responses in human subjects: modification of recording techniques.

Antidromically evoked facial nerve response was first introduced by Bumm and his coworkers in 1974 [1] as the only method to evaluate function of the facial nerve in the temporal bone. This response allow us to diagnose the degenerating process of the facial nerve earlier than the neurophysiological tests wich are currently in use, such as electroneurography [2, 3]. However, this small response with short latency is easily interfered with by initial stimulus artifacts and compound muscle action potentials in clinical cases. In this study, we tried various kinds of recording techniques and we show our method of recording the nerve response in human subjects.

Vulnerability of the Facial Nerve in Entrapment Palsy: Comparative Study in Guinea Pigs and Humans

The rationale for facial nerve decompression is to release the facial nerve and its vessels from entrapped compression. We have been investigating the possibility and timing of facial nerve entrapment in the facial canal in the early stages of its damage. We also studied differences between cross-sectional area ratios — facial nerve to facial canal (FN/FC) — of human adult and child temporal bones [1]. We revealed that the FN/FC ratio of children is significantly smaller than that of the adults. We report results of our experiments on the swelling changes of damaged facial nerves with time in guinea pigs [2]. We wanted to find out whether the experimental data of guinea pigs are applicable to human pathology. The aim of this paper is to measure the FN/FC ratios in guinea pigs and to show that the facial nerve of the guinea pigs is useful for an experimental model of entrapped facial palsy in humans.