Equilibrium Dysfunction Research Articles

Investigation of Post-Earthquake Dizziness After 2023 Türkiye Earthquakes: An Observational Case-Control Study.

The primary objective of this study was to investigate the etiological causes and the underlying mechanism of post-earthquake dizziness in affected persons. The present study utilized an observational case-control design to recruit 69 participants (33 with self-reported dizziness complaints and 36 healthy persons) who were exposed to the 2023 earthquakes in Türkiye. The participants underwent assessments including the Dizziness Handicap Inventory for measuring dizziness-related disability, stress, and anxiety assessment using various scales, and equilibrium evaluation through the use of videonystagmography, video head impulse test, and vestibular evoked myogenic potential. The 2 groups were compared based on these assessments. The results indicate that the Dizziness Handicap Inventory score was significantly higher in the patient group compared to the control group (P < .001). The mean score of the Peritraumatic Distress Inventory, as well as the mean scores of the Hospital Anxiety and Depression Scale anxiety score and depression score, were found to be significantly higher in the patient group compared to the control group (P=.012, P < .001, and P < .001, respectively). Furthermore, it was observed that the mean vestibulo-ocular reflex gain of the left posterior semicircular canal exhibited a statistically significant decrease in the patient group (P=.02). The observed equilibrium dysfunction experienced by individuals following a significant earthquake is likely attributable to heightened stress and anxiety stemming from multiple sources, including the impact of recurrent vibrations on the inner ear. Therefore, it is essential to establish a holistic healthcare approach that addresses the psychological needs of individuals affected by earthquakes.

Novel morphological and molecular data for Nasitrema spp. (Digenea: Brachycladiidae) in the East Asian finless porpoise (Neophocaena asiaeorientalis sunameri)

The East Asian finless porpoise, Neophocaena asiaeorientalis sunameri, ranks among the most endangered species with rapidly decreasing population in the Northwest Pacific. Trematode parasites of the genus Nasitrema that inhabit the air sinuses, inner ear, and the central nervous system of cetaceans frequently cause equilibrium dysfunction, disorientation, interference with echolocation, incoordination, and nervous system degeneration. Due to their specific location and associated pathologies, they have been recognized as one of the causes of cetacean strandings. Stranding data provides crucial information on the species’ biology, population health, and on the status of entire marine ecosystem. However, published data on parasite-induced standings that include information on the causative parasite pathogens are scarce. As part of a wider survey on the causes of East Asian finless porpoise strandings along the west coast of Korea, herein, we provide novel morphological and molecular data on two sympatric species of Nasitrema, namely, Nasitrema spathulatum and Nasitrema sunameri based on newly collected specimens from a stranded alive East Asian finless porpoise at the West coast of Korea. Our study adds a new distribution record for important parasite pathogens in cetaceans and provides the first molecular data for the parasite species recovered, which enabled us to re-evaluate the species relationships within the family Brachycladiidae, a group of important parasite pathogens of marine mammals.

Quantitative Changes in Gait Parameters after Cycling among Multiple Sclerosis Patients withAtaxia:APilot Study

Introduction: Cerebellar ataxia is a common symptom of multiple sclerosis (MS), particularly in progressive forms, where gait and balance problems are the most debilitating symptoms. Exercise training is a critical component of rehabilitation in managing equilibrium dysfunction, and stationary bicycling is a safe, feasible, and effective method to reduce the symptom. Clinical walking performance tests are typically used to assess gait in these patients. However, gait analysis technologies are more sensitive and accurate at detecting subtle and subclinical changes. The purpose of this study was to determine the changes in gait parameters in MS patients with ataxic gait after using a stationary bicycle.&#x0D; Materials and Methods: Ten secondary progressive MS patients with ataxic gait and a mean expanded disability status scale (EDSS) of four were recruited. The participants cycled on a stationary bike. Gait analysis was performed before and after 12 sessions of cycling. It included spatiotemporal and balance parameter measurements.&#x0D; Results: Gait analysis showed statistically significant changes in spatiotemporal parameters, including speed (P=0.02, r=-0.51), and stride length (P=0.01, r=-0.63). Of balance-related indices, the mediolateral (ML) center of pressure (COP) displacement, anterior and posterior COP overshoot, and COP velocity changes were statistically remarkable after the intervention respectively. (P=0.01, r=-0.63), (P=0.02, r=-0.51), (P=0.03, r=-0.49), (P=0.01, r=-0.54).&#x0D; Conclusion: Gait analysis is applicable to track changes following rehabilitation in individuals with MS. The results indicate that using a stationary bicycle can improve some spatiotemporal and COP-related parameters.

Electronystagmography in 166 patients with acoustic neuroma before and after surgery

ObjectiveTo analyze the preoperative patterns of caloric test, eye tracking test (ETT), and optokinetic pattern (OKP) in patients with acoustic neuroma (AN) and compare them with the postoperative patterns of ETT and OKP results MethodsA total of 166 patients with AN (102 women; mean age: 41 years, range: 11–79 years) who were being treated at our hospital between 2013 and 2016 were enrolled. Preoperatively, a detailed history was taken regarding the presence of subjective symptoms of equilibrium dysfunction, and the patients underwent caloric test, ETT, and OKP. They were classified into three groups based on the preoperative ETT and OKP results as follows: Group A, normal ETT and OKP; Group B, either ETT or OKP was abnormal; and Group C, both ETT and OKP were abnormal. All patients were evaluated for subjective symptoms of vestibular dysfunction and were also grouped based on the tumor size on imaging. All surgeries were performed by a neurosurgeon using the lateral suboccipital retrosigmoid approach. About one month later after surgery, postoperatively ETT was performed on 150 patients and OKP was performed on 148 patients. The preoperative and postoperative ETT and OKP results were compared. The same two specialists analyzed the postoperative ETT and OKP findings as improved, unchanged, or worse. Student t-test was used for statistical analysis and a P-value of <0.05 was considered to indicate a statistically significant difference. ResultsThe average canal paresis(CP) % was 65.8%. No correlation was found between tumor size and CP%. The other side, the average tumor size in each group was 26.6 mm, 28.7 mm, and 37.8 mm in the Group A, B, and C, respectively. The average tumor size in Group C was significantly greater than those of Group A and B (P<0.01). The presence of gait disturbance in Group C was significantly higher than the other groups (P<0.01). The other side, abnormal ETT and OKP were seen in 32.5% and 31.9% of all patients, respectively. ETT and OKP results improved postoperatively in 67.4% and 68.9% of these patients. ConclusionsAbnormal ETT and OKP results showed positive correlations with the tumor size and presence of subjective symptoms. Further, dysfunction of cerebellum and brain stem owing to tumor compression was observed to recover in many cases after surgery.

Clinical characteristics with long-term follow-up of four Okinawan families with moderate hearing loss caused by an OTOG variant

We describe the clinical features of four Japanese families with moderate sensorineural hearing loss due to the OTOG gene variant. We analyzed 98 hearing loss-related genes in patients with hearing loss originally from the Okinawa Islands using next-generation sequencing. We identified a homozygous variant of the gene encoding otogelin NM_001277269(OTOG): c.330C>G, p.Tyr110* in four families. All patients had moderate hearing loss with a slightly downsloping audiogram, including low frequency hearing loss without equilibrium dysfunction. Progressive hearing loss was not observed over the long-term in any patient. Among the three patients who underwent newborn hearing screening, two patients passed the test. OTOG-associated hearing loss was considered to progress early after birth, leading to moderate hearing loss and the later stable phase of hearing loss. Therefore, there are patients whose hearing loss cannot be detected by NHS, making genetic diagnosis of OTOG variants highly useful for complementing NHS in the clinical setting. Based on the allele frequency results, hearing loss caused by the p.Tyr110* variant in OTOG might be more common than we identified. The p.Tyr110* variant was reported in South Korea, suggesting that this variant is a common cause of moderate hearing loss in Japanese and Korean populations.

Sudden onset of static equilibrium dysfunction in patients receiving a cochlear implant.

Background:We investigated the sudden onset of static equilibrium dysfunction caused by cochlear implantation (CI) in congenital hearing loss patients.Method:Twenty-five patients were selected from a cohort of unilateral CI recipients to form the CI group. Static posturography was performed 1 to 3 days before and 3 to 5 days after CI. Each patient underwent the test with eyes open (EO) and eyes closed (EC) for 30 seconds, separately. Another group of age- and sex-matched patients with no history of hearing impairment undergoing unrelated surgeries formed the control group, and were examined with the same tests pre- and post-surgery. A third group of patients undergoing middle ear surgery formed the otitis media (OM) group. Postural sway parameters including sway velocity (SV) in the X-axis, SV in the Y-axis, length of sway locus length (LNG), and environmental area (ENV) were measured and recorded.Results:Comparison of pre-surgery posturographical parameters between the CI and control groups revealed no significant differences. Significant differences were found in most parameters in pre- and post-surgery comparisons in the CI group. Mean SV values in the X-axis pre- and post-surgery were 8.48 and 11.52 mm/s, respectively, in the EO condition (P < .05), and 14.94 and 20.16 mm/s, respectively, in the EC condition (P < .05). In the Y-axis, mean SV values were 15.36 and 20.24 mm/s pre- and post-surgery, respectively, in the EC condition (P < .05). The LNG values in the CI group pre- and post-surgery were 319.60 and 469.88 mm in the EO condition (P < .05), and 571.40 and 764.12 mm in the EC condition (P < .05). No significant functional equilibrium change was observed in the control group between pre- and post-surgery (P > .05) except SV in the X-axis and LNG in the EO condition (P < .05). No significant pre- and post-surgery differences were found in the OM group.Conclusion:CI appeared to influence static equilibrium function within 1 week post-surgery. This influence was greater when eyes were closed.

Neural Stem Cell Transplantation Is Associated with Inhibition of Apoptosis, Bcl-xL Upregulation, and Recovery of Neurological Function in a Rat Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is a common disease that usually causes severe neurological damage, and current treatment is far from satisfactory. The neuroprotective effects of neural stem cell (NSC) transplantation in the injured nervous system have largely been known, but the underlying mechanisms remain unclear, and their limited sources impede their clinical application. Here, we established a rat model of TBI by dropping a weight onto the cortical motor area of the brain and explored the effect of engrafted NSCs (passage 3, derived from the hippocampus of embryonic 12- to 14-d green fluorescent protein transgenic mice) on TBI rats. Moreover, RT-PCR and Western blotting were employed to investigate the possible mechanism associated with NSC grafts. We found rats with TBI exhibited a severe motor and equilibrium dysfunction, while NSC transplantation could partly improve the motor function and significantly reduce cell apoptosis and increase B-cell lymphoma–extra large (Bcl-xL) expression at 7 d postoperation. However, other genes including Bax, B-cell lymphoma 2, Fas ligand, and caspase3 did not exhibit significant differences in expression. Moreover, to test whether Bcl-xL could be used as a therapeutic target, herpes simplex virus (HSV) 1 carrying Bcl-xL recombinant was constructed and injected into the pericontusional cortices. Bcl-xL overexpression not only resulted in a significant improvement in neurological function but also inhibits cell apoptosis, as compared with the TBI rats, and exhibits the same effects as the administration of NSC. The present study therefore indicated that NSC transplantation could promote the recovery of TBI rats in a manner similar to that of Bcl-xL overexpression. Therefore, Bcl-xL overexpression, to some extent, could be considered as a useful strategy to replace NSC grafting in the treatment of TBI in future clinical practices.

Disturbances in equilibrium function after major earthquake

Major earthquakes were followed by a large number of aftershocks and significant outbreaks of dizziness occurred over a large area. However it is unclear why major earthquake causes dizziness. We conducted an intergroup trial on equilibrium dysfunction and psychological states associated with equilibrium dysfunction in individuals exposed to repetitive aftershocks versus those who were rarely exposed. Greater equilibrium dysfunction was observed in the aftershock-exposed group under conditions without visual compensation. Equilibrium dysfunction in the aftershock-exposed group appears to have arisen from disturbance of the inner ear, as well as individual vulnerability to state anxiety enhanced by repetitive exposure to aftershocks. We indicate potential effects of autonomic stress on equilibrium function after major earthquake. Our findings may contribute to risk management of psychological and physical health after major earthquakes with aftershocks, and allow development of a new empirical approach to disaster care after such events.

Investigation of patients with presbyastasis using the cross test

To investigate the equilibrium function of elderly patients experiencing dizziness caused by age-dependent physiological vestibular dysfunction (presbyastasis) and to evaluate the effects of a vestibular rehabilitation program, the author conducted a new balance training program, referred to as the cross test. Nine patients over the age of 65 years who had presbyastasis and who had complained of equilibrium dysfunction for at least 6 months were enrolled in this study. A standing balance training system with a gravicorder was used to examine the patients' equilibrium. The cross test indicates the equilibrium function based on ankle mobility and the center of gravity when individuals successively move forward, backward, right, and left on the gravicorder. The cross test was performed every one or two months for a total of at least 5 times; the results were then analyzed statistically. After participating in the vestibular rehabilitation program, the range of ankle motion improved in all 9 patients, compared with the pretraining values (p<0.001). These findings suggested that the cross test is a reliable method for estimating equilibrium function and the effects of a balance training program in patients with presbyastasis. Furthermore, the test appears to be associated with a prompt improvement in equilibrium dysfunction and thus may be an effective therapeutic option, in conjunction with medication and conventional vestibular training programs.

Evidence for Improved Neuropharmacological Efficacy and Decreased Neurotoxicity in Mice with Traditional Processing ofRhizoma Arisaematis

Rhizoma Arisaematis (RA, the rhizome of Pinellia pedatisecta Schott) is a traditional Chinese medicine commonly used in the treatment of convulsions, inflammation, and cancer. Despite the fact that it has been used for more than 2000 years, the pharmacological and toxic effects of traditionally processed products of RA are still unclear. In this study, we attempted to investigate the effects exerted by untreated crude RA and different preparations of RA treated with alumen in combination with ginger juice (Zhinanxing) or bile juice (Dannanxing) in ICR mice. The results showed that both the Zhinanxing and Dannanxing water extracts exerted significantly increased sedative effects, as indicated by the inhibitory effects on ambulatory distances, jumps, vertical-plane entries, and prolonged pentobarbital-induced sleeping time. The extracts also exerted significantly increased analgesic effects (increase of tail flick latency in nociceptive testing) in mice than did the unprocessed crude RA after oral administration for one to three days, and effects persisted 18 days after the cessation of treatment. By contrast, the toxic effects, such as an increase in stereotype-1 episodes of locomotor activities and reduction of the retention time on a rotating rod (motor equilibrium dysfunction), were observed only in mice treated with the unprocessed crude RA for three consecutive days, and effects persisted for 18 days after the cessation of treatment. These neurotoxic effects were accompanied by an increase in plasma lipid peroxidation (LPO), decrease in whole blood nitric oxide (NO(x)) levels, and inhibition of Na(+)/K(+)-ATPase activities in membrane fractions of erythrocytes and in the cerebral cortex. In conclusion, these findings provide scientific evidence that the processed RA indeed possesses not only enhanced neuropharmacological efficacy but also reduced neurotoxic effects as compared to the unprocessed crude RA. The signaling of NO(x)/oxidative stress/Na(+)-K(+)- ATPase activities played a role, at least in part, in the underlying mechanisms of neurotoxic effects induced by the crude RA.

脳幹部血流に対するプロスタグランディンＥ１の影響

Posterior circulation disturbance, commonly known as vertebrobasilar insufficiency (VBI), is often associated with symptoms such as vertigo and instability. These various symptoms are thought to be due to hemodynamic disorders of the vertebrobasilar circulation that temporarily damage the vestibular nucleus (VN) and/or the cochlear nucleus (CN) within the brainstem. In this study, using a Laser-Doppler approach, we investigated the brainstem blood flow (BBF) feeding the vertebrobasilar system in order to estimate the influence of continuous intravenous infusion of prostaglandinE1 (PGE1), which acts as a microvascular dilator, in normal rats in this study. The following results were obtained. 1. During continuous intravenous infusion of PGE1 (at doses of 5 and 10ng/min/kg), no significant fluctuations of physiological parameters (PaO2, PaCO2, pH, saturation, body temperature, mean arterial blood pressure) were observed. However, the mean arterial blood pressure showed a tendency to decline after 45 minutes of continuous infusion of the higher dose (10ng/min/kg). 2. The BBF in the rats increased significantly to about 120% of the initial level after 30 minutes of continuous infusion of PGE1, compared to control infusion of saline. 3. Dose-dependent increases in the BBF were apparent after 60 minutes' continuous infusion. Considering the particular construction of the perforating vessels within the brainstem in both the VN and CN, the BBF measured in this investigation sensibly reflects is considered to reliably reflect the blood flow in these two nuclei. Therefore, we conclude that continuous intravenous infusion of PGE1 might be efficacious in cases of vertigo, equilibrium dysfunction and hearing impairment which directly result from circulation disturbances of the brainstem, because PGE1 would increase the blood flow to the VN and CN via improvement of the microvascular circulation within the brainstem.

Photochemically induced equilibrium dysfunction in the hamster model with evaluation by means of a new globe rotatory test system.

Thrombosis in the inner ear is regarded as one of the causes of equilibrium dysfunction. We have established an experimental thrombosis model by producing a photochemical reaction between rose bengal and green light, and have evaluated the dysfunction with a new rotatory test system. Hamsters were treated with tissue-type plasminogen activator (tPA) in doses of 0, 0.13, 0.26, and 0.52 mg/kg. The equilibrium dysfunction of the hamsters was evaluated by scoring their behavior according to visual observation and by measuring their time on the rotatory test system. Treatment of animals with sufficient tPA (> or = 0.26 mg/kg) caused a significant amelioration of the behavior and a concomitant significant prolongation of time on the rotating globe. These findings suggest that the equilibrium dysfunction induced by the photochemical reaction was due to the thrombi formed, and that our test system may provide a useful tool for evaluating equilibrium dysfunction in hamsters.

P-401 - Effect of ATP on a model of equilibrium dysfunction due to hemilateral vestibular disorders in guinea pigs

P-401 - Effect of ATP on a model of equilibrium dysfunction due to hemilateral vestibular disorders in guinea pigs

P-378 - Evaluation of fibrinolytic system in microvasculation using an equilibrium dysfunction model of mice deficient in uPA, tPA and PAI-1

P-378 - Evaluation of fibrinolytic system in microvasculation using an equilibrium dysfunction model of mice deficient in uPA, tPA and PAI-1

Effect of lipo-pro-prostaglandin E 1, AS-013 on rat inner ear microcirculatory thrombosis

We investigated effects of lipo-pro-prostaglandin E 1 (lipo-[11α, 13E, 15S]-11,15-dihydroxy-9-[1-oxobutoxy]-prosta-8, 13-dien-1-oic acid butyl ester), AS-013 in two models of hearing disturbance and equilibrium dysfunction induced by rat inner ear microcirculatory thrombosis. Inner ear microcirculatory thrombosis was induced by photochemical reaction between systemic injection of Rose Bengal and irradiation of green light to the cochlea and vestibule. Photochemical reaction causes endothelial injury followed by platelet adhesion, aggregation and formation of a platelet- and fibrin-rich thrombus. In the hearing disturbance model, a compound cochlear nerve action potential was recorded by electrocochleography every minute. Photochemical reaction induced inner ear microcirculatory thrombosis, followed by disappearance of the action potential. AS-013 significantly ( P<0.05) prolonged time to disappearance of the action potential compared with control group. In the equilibrium dysfunction model, the irradiation to the vestibule was applied for 10 min after Rose Bengal injection. The behavior of rats in the swimming test and nystagmus were observed 24 h after the completion of irradiation. In the swimming test, two of 12 animals treated with AS-013 showed no rotating about their longitudinal axes, which indicates equilibrium dysfunction and the duration of well-balanced swimming prolonged. AS-013 suppressed the appearance of nystagmus. These results suggest that lipo-pro-prostaglandin E 1, AS-013 may prevent hearing disturbance and equilibrium dysfunction due to inner ear microcirculatory disorders.

難聴・めまいで初発した結節性動脈周囲炎例

A 67-year-old female visited our hospital with a complaint of progressive bilateral hearing loss and recurrent attackes of vertigo. An audiogram showed bilateral sensory neural hearing loss with positive recuruitment phenomenon. The caloric test showed bilateral canal paresis. The galvanic body sway test showed a normal response. From these results, we concluded that the hearing loss, dizziness and equilibrium dysfunction were due to a disorder of the inner ear. The results of a glycerol test and furosemide VOR test suggested endolymphatic hydrops in the inner ear. The patient was treated with steroid and prostaglandin I2. Her dizziness subsequently disappeared, but her hearing loss was not improved. After discharge from our hospital, she entered another hospital because of a high grade fever and muscular pain. Laboratory data suggested an autoimmune disease and renal failure. She was diagnosed with periarteritis nodosa on the basis of clinical findings and pathological findings following a kidney biopsy.

Effect of prostaglandin E 1 on the rat inner ear microvascular thrombosis

1. 1. The effect of prostaglandin E 1 was investigated with a two-rat model of hearing disturbance and equilibrium dysfunction associated with inner ear microvascular thrombosis. 2. 2. The inner ear microvascular thrombosis was induced by photochemical reaction between Rose Bengal and transmural green light (540 nm). Photochemical reaction causes endothelial injury followed by platelet adhesion, aggregation, and formation of a platelet- and fibrin-rich thrombus. 3. 3. Under anesthesia, the cochlea or the vestibule was irradiated with green light to induce hearing disturbance or equilibrium dysfunction. 4. 4. In the hearing disturbance model, a compound cochlear nerve action potential was recorded by electrocochleography every minute after the beginning of photoirradiation in the presence of Rose Bengal. 5. 5. In the equilibrium dysfunction model, the photoirradiation was applied for 10 min after Rose Bengal administration. The behavior of rats was observed in the swimming test, and nystagmus was observed 24 hr after the end of photoirradiation. 6. 6. Prostaglandin E 1 significantly ( P<0.05) prolonged the time required to suppress the action potential. In the swimming test, 3 of the 6 animals treated with prostaglandin E 1 did not rotate about their longitudinal axes (equilibrium dysfunction) and the duration of well-balanced swimming was significantly prolonged ( P< .001). Prostaglandin E 1 significantly ( P<0.05) suppressed the appearance of nystagmus. 7. 7. In conclusion, prostaglandin E 1 potentially prevents hearing disturbance and equilibrium dysfunction due to inner ear microvascular disorders.

Effect of a Ca 2+ entry blocker, nilvadipine, on hearing disturbances and equilibrium dysfunction caused by microcirculatory disorders of the rat inner ear

We evaluated the effects of Ca 2+ entry blockers, nilvadipine and flunarizine, on microcirculatory disorders of the inner ear and on blood flow in the inner ear of rats. Under sodium pentobarbital anesthesia, the middle ear was opened by a ventrolateral approach. A green light (wave length 540 nm) was applied to the cochlea or the vestibule to induce a hearing disturbance or equilibrium dysfunction as a result of of inner ear microcirculatory disorders, while rose bengal solution was infused intravenously. In a hearing disturbance model, a compound cochlear nerve action potential was recorded by electrocochleography every minute after the beginning of illumination. The sound stimulus was an 8 kHz sine wave 100 dB normal hearing level. The action potential was calculated 128 times. The action potential disappeared about 12 min after the beginning of illumination. In another model of equilibrium dysfunction, the photoillumination was applied for 40 min under the infusion of rose bengal. The behavior of rats was observed in the swimming test and nystagmus was recorded 24 h after the completion of photoillumination. In a separate experiment, blood flow in the inner ear was measured with a laser Doppler flowmeter under sodium pentobarbital anesthesia. In this study, both nilvadipine and flunarize prolonged the time required for complete suppression of the action potential, prevented equilibrium dysfunction in the swimming test and reduced the occurrence of nystagmus. Flunarizine significantly increased inner ear blood flow and nilvadipine failed to decrease blood flow in the inner ear, despite a reduced systematic blood pressure. In conclusion, Ca 2+ entry blockers may prevent microcirculatory disorders of the inner ear in rats.

Functional and pathohistologic changes in an ischemic model of rat inner ear

We investigated functional and histopathological changes in the inner ear circulatory disorder caused by thrombosis of the anterior inferior cerebellar artery (AICA) in rats. The thrombosis was induced by a photochemical reaction between green light and systemic injection of Rose Bengal. During this experiment, auditory brainstem responses (ABR) were recorded and cochlear blood flow (CBF) was measured by a laser doppler flowmeter. Within 5 weeks after the procedure, histopathological changes were studied by light microscopy following the observation of equilibrium dysfunction and ABR recording. CBF was reduced from the baseline in 30.8 +/- 3.4% (mean +/- SE, n = 25) by occlusion of the AICA, ABR was altered in 96% of animals, and equilibrium dysfunction was observed in 77%. When the AICA was not reopened within a short time, severe histopathological changes were frequently observed. There was no significant correlation between equilibrium dysfunction and histopathological changes in the vestibule. It is concluded that this experimental model may be useful for investigating functional and histopathological changes in the ischemic inner ear.

Effect of Ibudilast on Microcirculation Thrombosis in Rat Inner Ear

The effect of ibudilast (0.1, 0.3mg/kg), which has cerebral vasodilating and antiplatelet effects, was evaluated in two models of rat inner ear microcirculation thrombosis by using the photochemical reaction between green light (wave length: 540 nm) and intravenous injection of rose bengal. Furthermore, the inner ear blood flow was measured by a laser-Doppler flowmeter. In the hearing disturbance model, under anesthesia, the compound action potential of the cochlear nerve (AP) was measured by an electrocochleogram. The sound stimulus was an 8-kHz sine wave at 80 dB SPL. The AP was calculated 128 times. In the controls, the AP disappeared about 4 min after the intravenous injection of rose bengal (20mg/kg). The time required to completely suppress the AP in the animals treated with ibudilast (0.1, 0.3 mg/kg) was significantly prolonged as compared with that in the controls. In the equilibrium dysfunction model, ibudilast (0.1, 0.3 mg/kg) reduced the time of abnormal swimming in the swimming test 24 hr after the completion of photo-illumination. Ibudilast (0.3 mg/kg) increased the inner ear blood flow during the 10-min observation period as compared with the controls, while it did not affect the mean blood pressure. In conclusion, ibudilast increased the inner ear blood flow and was effective in two models of rat inner ear microcirculation thrombosis.