The histaminergic neuronal system and three types of histamine receptors, H1, H2 and H3 receptors, have been identified in the brain and both histaminergic innerva-tion and the presence of all three histamine receptors have been demonstrated in the vestibular nucleus. Brain-penetrating H1 antagonists have been clinically used for the treatment of vertigo or motion sickness and recently, betahistine, a weak H1 agonist with a potent H3 antagonistic activity, was introduced in the treatment of vertigo, demonstrating the significance of brain histamine in the pathophysiology of vestibular function. In animal experiments, either unilateral vestibular caloric stimulation or hyper-gravity stimulation activates the histaminergic system, which may promote the symp-toms associated with vertigo or motion sickness such as nausea and vomiting. However, the direct effects of histamine on the neurons in the vestibular nucleus remain con-troversial. In vivo studies reported that the firing rates of most neurons in the vestibu-lar nucleus were decreased by histamine via H2 receptors. However, in vitro applications of histamine caused membrane depolarization and increased the firing rate via H2 receptors. In addition to these direct actions on vestibular neurons, histamine or betahistine increases the cerebral and inner ear blood flows, which may contribute to the therapeu-tic benefit for vertigo. H3 ligands including betahistine are expected to be a promising drug both in the clinical and the laboratory research of the vestibular pathophysiology.
The diagnosis, sex ratio and age-distribution were investigated in 1, 301 patients, who visited the Neuro-otological Clinic and the Laboratory of Equilibrium Function in Kitasato University Hospital, Sagamihara City, in a 3 year period from January 1996 to December 1998. The percentage of people aged over 60 years old was 14.8% of the total population in Sagamihara city, but patients aged over 60 years old represented 37.4% of the total patients in Kitasato University Hosipital and 33.6% of the total patients in the Neuro-otological Clinic. The patients in the Neuro-otological Clinic were classified into 4 groups by diagnosis; peripheral vestibular disorders (19.1%), diseases of the CNS (8.3%), generalized disorders (3.9%), and others (68.8%). However, the percentage of peripheral vestibular disorders decreased from 19.1 to 11.7% and the percentage of CNS diseases increased from 8.3 to 16.9% in patients aged over 60 years old. Peripheral vestibular disorders included Meniere's disease, benign paroxismal positional vertigo, vestibular neuritis, sudden deafness and delayed hydrops in the 4th and 5th decades. The increase in the percentage of diseases of the CNS in elderly patients was accompanied by increases in cerebrovascular disease and vertebrobasilar insufficiency in the 6th decade.
In order to evaluate the precise intervals for successive caloric irrigations of the bilateral ears, a total of 72 normal ears (36 persons) and eight ears with central perforated tympanic membrane were examined using a caloric stimulus with 20 ml water at 20 degrees centigrade for 20 s. Nystagmus was examined using infrared CCD Frenzel spectacles, and the parameters were recorded on an electro nystagumograph. For normal ears temperature changes of the ear canal following irrigation were examined using an infrared tympanic thermometor and changes in the promontory of the perforated ear were examined by microthermistor via the perforatin. For normal ears nystagmus on ENG ceased after 288 s (mean+2 s.d.), and using CCD spectacles it ceased after 336 s. For perforated ears ENG stopped after 258 s. Thus, the waiting time for successive caloric irrigations of the bilateral ears was 5.6 minutes. In addition, since it took 15 minutes for the temperatures of the normal ear canal to return to the original temperature, the waiting time for the same ear was 15 minutes.
In collaboration with otologists and psychotherapists, psychotherapy was performed together with the administration of drugs for patients with Meniere's disease in whom medical treatment, surgical treatment, or intratympanic streptomycin therapy had been ineffective and for a patient with intractable tinnitus. We report in detail 7 patients for whom psychotherapy was effective for vertigo, stabilization of hearing fluctuation, or the acceptance of tinnitus. It is important to consider psychosomatic aspects in the treatment of patients with Meniere's disease, and it was possible to avoid unnecessary surgery in some Meniere's disease patients using a combination of psychotherapy with medication.
The effects of surgical manipulation to the vestibular system have not fully been elucidated and this study was designed to investigate the effects of tympanoplasty and cochlear implant on positional nystagmus. Materials and methods: (1) Tympanoplasty: A total of 42 patients were included in this study and the etiological diagnosis of the patients were 26 cases of cholesteatoma and 22 cases of chronic otitis media. Types of tympanoplasty were type I, 12 cases; type III, 26 cases; type IV, 7 cases; and first-stage operation, 3 cases. The positional nystagmus was monitored and video-recorded using an infrared CCD camera before surgery, one day and every several days after surgery until it disappeared. (2) Cochlear implant: The etiological diagnoses of these patients were 5 cases of progressive hearing loss, 4 cases of meningitis, 2 cases of sudden deafness and 6 cases of unknown etiology. Vestibular function was evaluated before and after surgery using the caloric test and the positional nystagmus. Results: (1) Tympanoplasty: Postoperative positional nystagmus was observed in 19 out of the 42 cases (45.2%), all of which showed no nystagmus prior to surgery. The direction and type of the nystagmus varied and it was toward the surgical side in 13 cases, downbeat nystagmus in 4 and apogeotropic direction-changing positional nystagmus in 2. Postoperative nystagmus disappeared 4 to 68 days after surgery. (2) Cochlear implant: Postoperative positional nystagmus was observed in 6 out of 11 cases (54.5%), all of which showed no nystagmus prior to surgery. The type of nystagmus was toward the surgical side in all cases. Postoperative nystagmus disappeared 8 to 26 days after surgery. Reduced results of caloric testing after surgery were found in 3 of 14 cases with residual vestibular function. Conclusions: Tympanoplasty and cochlear implant have a significant effect on the vestibular system. However, vestibular changes after these surgeries were considered to be reversible.
There have been many reports of patients with Acoustic Neurinoma (AN) with an atypical course and clinically we have also encountered many cases of AN with sudden onset of sensorineural hearing loss (SNHL). However, cases of AN with sudden profound SNHL are very rare. In this report, we describe 3 cases of AN with sudden onset of profound SNHL and rotary vertigo. In all 3 cases the AN were small. One patient recovered nearly all of his normal hearing ability. Even with the use of magnetic resonance imaging (MRI), two cases could not be diagnosed the first time, and one of these two cases was diagnosed with permanent hearing loss at a previous hospital. In this patient radiological findings at 6 months from onset showed the existence of AN. The other case has been followed at our hospital and a diagnoses of AN was made 2 years and 5 months after onset. None of the three cases showed any characteristic findings of idiopathic sudden SNHL, which made diagnosis difficult, particularly since radiological examinations such as MRI suggested normal findings. In patients with SNHL, careful long-term follow we should be performed.