Hearing and balance constitute the essential senses in human beings as well as in animals. Cochlea and vestibule are the peripheral organs that mediate these senses. The acoustic energy from outside, when reached cochlear hair cells, i.e., the primary receptors, is transformed to electrical signals. From a couple of decades ago, the specialized signal transduction in hair cells has been explored mainly by using electrophysiological approaches. Recent molecular biological dissections have revealed that the network of many functional molecules establishes the unique physiology of hair cells. Furthermore, it has been identified that the mutations of several molecules expressed in hair cells may cause hearing impairments. In this review, the authors discussed relationships between dynamic physiology and its molecular basis in hair cell activities.
We studied the influence of sleep restriction on standing posture in 10 healthy volunteers (6 men and 4 women), aged 19 to 24 years (mean, 21.4 years), with normal hearing and vestibular function and no history of leg trauma. They were examined under three conditions: in the morning after sleeping well, in the morning after remaining awake all night, and in the afternoon after remaining awake all night. Each subject was asked to stand on a stabilimeter fixed on a platform attached to a rotating device. We examined the stability of each subject's stance while the platform was stationary and while it was rotating clockwise at a speed of 60 deg/s. At the same time, they underwent a test of mental arithmetic for 20 minutes (Uchida-Kraepelin test). The total length of traces of the center of pressure and its perturbation area, when they were measured while the platform was stationary, was significantly (p<0.05) increased under the condition of sleep restriction. We concluded that sleep restriction degrades the ability of body balance, even in normal young people.
Video-oculodraphy (VOG) has come into wide use recently. However, most systems on the market adopt commercialized video standards. When we record saccadic eye movement, this standard sampling time (0.016 ms) could limit the accuracy of recording. In order to evaluate the reliability of VOG-based examination of saccadic eye movement, horizontal saccade-recordings by VOG (SMI USA 3D-VOD/ver.5) were compared with those of electro-nystagmography (ENG). In ENG recordings, sampling time was modulated from 1 to 20 ms, and the data were obtained as digital figures through an analogue-digital converter. Simultaneous recordings of saccade ranging from 5 to 30 deg. at 5 deg. steps using VOG and ENG revealed relatively low maximum velocities (from 30% at 5 deg to 70% at 30 deg) in VOG. ENG recordings with a sampling time from 1 to 20 ms at 1 ms steps demonstrated that frequent samplings could improve the accuracy of recording maximum eye velocity. With a 16 ms sampling time, peak eye velocity was nearly consistent with that of VOG. This suggests that the low value of saccadic velocity with VOG depends on the long sampling time. In order to obtain appropriate numerical values of peak eye velocity, a sampling time of less than 6 ms would be required. In addition, the present study demonstrated a shorter latency at the onset of adduction rather than that of abduction, which could be caused by the different course of nerve conduction.
The relationship between Japanese traditional medical diagnosis and examination of equilibrium was studied. Spontaneous and positional nystagmus, and the results of sinusoidal rotatory test and Shellong test, which might be strongly related to the active stage in vertigo, were not relevant to Japanese traditional medical diagnosis. However, it is likely that the abnormal findings in caloric stimulation test or optokinetic nystagmus test which suggest the malfunction of the peripheral or central vestibular system are partly related to Japanese traditional medical diagnosis.
In this study, we reported the long term results of intratympanic gentamicin administration over 1 year after treatment for intractable Ménière's disease (MD) or delayed endolymphatic hydrops (DEH). Thirty-five patients (15 males and 20 females) were evaluated after 6.0 intratympanic gentamicin injections on average. The mean age was 44.5 years-old and the mean follow-up period was 68.2 months. The formula expressing the effect of treatment was based on AAOHNS criteria. Valid results of evaluation for more than twelve months in post-treatment were compared with those for six months in pre-treatment, expressed in percent. If the formula is 40% or less, the treatment is judged as effective. The efficacy rate of this treatment for definitive vertigo spells was 97%, and that for adjunct spells was 74%. The average hearing level of five frequencies before and after treatment was 68.5 dB and 74.0 dB, respectively. In eleven patients (31%), the hearing level deteriorated by 10 dB or more. Our results revealed that GM therapy was very effective in the long term for the treatment of vertigo. However, further refinement is needed to minimize adverse hearing deterioration. Methods to reduce adverse effects were discussed.
Over the past 5 years, 34 cases of dizziness caused by head and neck injury were experienced at the Department of Otolaryngology, Kanto Rosai Hospital. For the causes of injury, 15 of them were from traffic accident, 10 were from falls, 4 involved violence, 3 were sports, and 2 involved accidents at work. Twenty five cases involved occipital or temporal bone (several cases involved the neck), 6 cases were cervical injury (so called whiplash injury), and 6 cases were facial bone injury. All cases of facial injury had disordered maxillary and zygomatic bone. 10 cases required laboratory studies only, and the other 24 cases required diagnosis and treatment. In laboratory tests, abnormal findings were observed in 33% of cases in the carolic test, and 33% in the optokinetic pattern and eye tracking test. Findings of nystagmus were observed in 60% of cases. For the diagnosis of dizziness, 15 cases involved middle ear disorder, 7 were benign proximal positional vertigo, and 8 were cervical vertigo. For these patients, treatment involved medicine, rehabilitation and counseling. Almost all patients recovered within 1 year, but 6 cases were unchanged and continued treatment. Four of these 6 cases had a complication of recurrent headache or ear pain. Another 2 cases had trouble in the office or with communication. Dizziness in several patients concerned cervical injury. We considered that dizziness was caused by the difference of flow between both vertebral arteries. The mechanism of the difference in flow was concerned with the sympathetic nerve and receptor in deep muscle in the neck.
We report horizontal canal BPPV (HC-BPPV) on targeting its pathophysiology, horizontal semicircular canal function and prognosis together with a review of the literature. Nineteen patients were classified into 9 with canalolithiasis and 10 cupulolithiasis. Average curative periods were a mean time of 81 days for CP positive patients, and 24 days for those with a normal caloric response. The prognosis of patients with a normal caloric response was significantly better than that of patients with positive CP results. Factor which affect the prognosis of HC-BPPV also involve the effectiveness of physical therapy and the cause of recurrent and prolonged cases.
To evaluate the effect of neuro-otological findings on hearing recovery, the authors studied 327 patients with sudden deafness treated over the past five year period. Firstly, all patients were classified to four groups (grades 1, 2, 3 and 4) according to the grading system for idiopathic sudden deafness. Vertigo was present in 123 (37.6%) of all 327 patients, in 5 (23.8%) of 21 grade 1 group patients with slight hearing loss, and in 71 (65.4%) of 108 grade 4 group patients with profound hearing loss. Similarly, neuro-otological abnormalities such as nystagmus, canal paresis (CP) in the caloric test, and abnormal vestibular evoked myogenic potentials (VEMP) were found more frequently in the grade 4 group than in the grade 1 group. Hearing recovery was better in the grade 1 group (cured or markedly improved in 15 of 21 patients, 71.4%) than in the grade 4 group (cured or markedly improved in 51 of 108 patients, 47.2%). Similarly, hearing recovery was better in patients without vetigo (cured or markedly improved in 138 of 204 patients, 67.6%) than in patients with vertigo (cured or markedly improved in 57 of 123 patients, 46.3%). Patients the with neuro-otological abnormalities above-mentioned also showed poorer hearing recovery than those without abnormalities. We conclude that vertigo and neuro-otological abnormalities negatively affect hearing recovery of idiopathic sudden deafness.
Treadmill exercise has the specific aftereffect that, in stepping down onto the floor after exercise, a person has the perception of self-motion and sways forward. It has been speculated that treadmill exercise is accompanied by an adaptation process in the postural control system because of a mismatch between the visual and somatosensory input, and thus the aftereffect occurs as re-adaptation to normal postural control. However, nobody has yet succeeded in showing whether the extent of the mismatch between the visual and somatosensory input during treadmill exercise influences the aftereffect. In the present study, we used a video image of sufficient reality to induce self-motion perception, and changed the visual input during treadmill exercise to vary the mismatch level. As a result, the aftereffect was significantly reduced by normally-directed visual stimuli and significantly increased by reverse-directed visual stimuli. In conclusion, a correlation was found between the level of the mismatch and the aftereffect, supporting the view that aftereffects are caused by a mismatch of the visual and somatosensory input during treadmill exercise.