Maximum Slow Phase Eye Velocity Research Articles

Difference in the immediate effect on positional nystagmus for head positions with interval time during Epley maneuver: a randomized trial.

The Epley maneuver (EM) shows immediate effect, wherein disappearance of positional nystagmus occurs soon after the EM. Our previous study showed that setting interval times during the EM reduced the immediate effect. The purpose of this study is to identify the head position for which interval time reduces the immediate effect. Fifty-one patients with posterior canal type of benign paroxysmal positional vertigo (BPPV) were randomly assigned to the following three groups: 10min interval time set at the first head position of the EM in group A, at the third head position in group B, and at the fourth head position in group C. The primary outcome measure (POＭ) was the ratio of maximum slow-phase eye velocity of positional nystagmus soon after the EM, compared with that measured before the EM. A large ratio value indicates a poor immediate effect of the EM. The POＭ in group A (0.07) was smallest (B: 0.36, C: 0.49) (p < 0.001). The interval times at the third and fourth head positions reduced the immediate effect of the EM. Our previous study showed that the effect of BPPV fatigue is continued by maintaining the first head position of the EM. BPPV fatigue constitutes fatigability of positional nystagmus with repeated performance of the Dix-Hallpike test. Our findings may be interpreted in accordance with the theory that the immediate effect of the EM is BPPV fatigue itself, because we observed that the effect of BPPV fatigue is strongest in group A.

Increased Monocyte Chemotactic Protein-1 Accompanying Pro-Inflammatory Processes are Associated with Progressive Hearing Impairment and Bilateral Disability of Meniere’s Disease

Background: The progression of hearing impairment and the bilateral involvement of Meniere’s disease (MD) may depend on the disease duration and aging. Recent studies reported that MD might involve dysfunction of the microvascular circulation damaged due to inflammatory changes. Objectives: The aim of this study was to determine that the progress of the MD’s hearing impairment and bilateral disability may be associated with the pathogenesis of several pro-inflammatory processes. Patients and Methods: We recruited 30 unilateral MD patients (56.8 ± 14.7 years old), 7 bilateral MD patients (65.3 ± 13.9 years old), and 17 age-matched control subjects (53.5 ± 14.4 years old, p > 0.05). We measured the plasma vascular endothelial growth factor (VEGF), plasma interleukin-6 (IL-6), plasma tumor-necrosis factor α (TNFα), and plasma monocyte chemotactic protein-1 (MCP-1). Results: The bilateral MD group and the unilateral MD group had higher plasma MCP-1 (204.7 ± 41.0 pg/mL and 169.5 ± 32.0 pg/mL) than the control group (149.2 ± 30.7 pg/mL) (p < 0.05). There was no significant difference in plasma TNFα, IL-6, and VEGF among 3 groups (p > 0.05). There was a strong correlation between the plasma MCP-1 and age in MD patients (r = 0.58, p < 0.01); however, no significant correlation between the plasma MCP-1 and age was found in control subjects (p > 0.05). The plasma MCP-1 significantly correlated with the average hearing level of 500, 1,000, 2,000, and 4,000 Hz, and the maximum slow phase eye velocity in caloric test in the better side (p < 0.05). Also, the plasma MCP-1 showed significant positive correlations with the plasma IL-6 (r = 0.49, p < 0.01) and plasma TNFα (r = 0.32, p < 0.05) in MD group. Conclusions: Our results suggest that the increased plasma MCP-1 accompanying pro-inflammatory processes are associated with the progression of the hearing impairment and the bilateral disability of MD.

Effect of Sitting Position vs. Supine Position With the Head Turned to the Affected Side on Benign Paroxysmal Positional Vertigo Fatigue.

Objective: In benign paroxysmal positional vertigo (BPPV), positional nystagmus becomes generally weaker when the Dix–Hallpike test is repeated. This phenomenon is termed BPPV fatigue. We previously reported that the effect of BPPV fatigue deteriorates over time (i.e., the positional nystagmus is observed again after maintaining a sitting head position). The aim of this study was to investigate whether the effect of BPPV fatigue attenuates after maintaining a supine position with the head turned to the affected side.Methods: Twenty patients with posterior-canal-type BPPV were assigned to two groups. Group A received Dix–Hallpike test, were returned to the sitting position (reverse Dix–Hallpike test) with a sitting head position for 10 min, and then received a second Dix–Hallpike test. Group B received Dix–Hallpike test, were kept in the supine position with the head turned to the affected side for 10 min, and then received reverse Dix–Hallpike test followed by the second Dix–Hallpike test. The maximum slow phase eye velocity (MSPEV) of positional nystagmus induced by the first, reverse, and second Dix–Hallpike test were analyzed.Results: The ratio of MSPEV of the positional nystagmus induced by the second Dix–Hallpike test relative to the first Dix–Hallpike test was significantly smaller in group B than that in group A. There was no difference in the MSPEV of the positional nystagmus induced by the reverse Dix–Hallpike test between group A and B.Conclusions: The effect of BPPV fatigue is continued by maintaining a supine position with the head turned to the affected side, while the effect is weakened by maintaining a sitting head position. On the basis of the most widely accepted theory of the pathophysiology of BPPV fatigue, in which the particles become dispersed along the canal during head movement in the Dix–Hallpike test, we found an inconsistency whereby the dispersed otoconial debris return to a mass during the sitting position but do not return to a mass in the supine position with the head turned to the affected side. Future studies are required to determine the exact pathophysiology of BPPV fatigue.Classification of Evidence: 2b.

The Clinical Significance of the Failure to Perceive Vertigo in the Postcaloric Period Despite a Robust Caloric Response.

Purpose The purpose of this project was to explore the association between the perception of motion during caloric testing and two tasks associated with central vestibular processing: postural stability and visuospatial memory. Method This was a prospective study of 25 patients who were found to have nonvestibular etiologies of their symptoms and normal vestibular function test results and who underwent caloric testing with a mean maximum slow phase eye velocity for each irrigation of 15° or greater. Following each caloric irrigation, patients were asked whether they had any sensation of movement. Patients were grouped based on the presence or absence of motion during the caloric exam (motion perception vs. absent perception). Postural stability was assessed using computerized dynamic posturography, and visuospatial memory was assessed using a memory match card game application. Results There were no significant differences between groups on any measures of peripheral vestibular function. However, the Absent Perception Group showed greater postural instability during Condition 5 of posturography and performed significantly worse on a task of visuospatial working memory. Both age and absence of motion perception predicted abnormal performance on measures of postural stability and visuospatial working memory. Conclusions There appears to be clinical implications to a lack of motion perception during the caloric exam in patients with an otherwise normal peripheral vestibular system. Based on the current findings, we are unable to determine whether differences in postural stability and visuospatial memory were due to age or a central vestibular processing deficit.

Effects of Interval Time of the Epley Maneuver on Immediate Reduction of Positional Nystagmus: A Randomized, Controlled, Non-blinded Clinical Trial.

Objective: The Epley maneuver (EM) has an immediate effect: rapid reduction of positional nystagmus. Benign paroxysmal positional vertigo (BPPV) causes BPPV fatigue, which constitutes fatigability of positional nystagmus and vertigo with repeated performance of the Dix-Hallpike test; notably, BPPV fatigability becomes ineffective over time. We hypothesized that the immediate effect of the EM is caused by BPPV fatigue. Therefore, we suspected that performance of the EM with intervals between head positions would worsen the immediate reduction of positional nystagmus in patients with BPPV, because BPPV fatigability would become ineffective during performance of this therapy.Methods: Forty patients with newly diagnosed BPPV were randomly assigned to the following two groups; one group performed the EM without intervals between positions (group A), and the other group performed the EM with 3 min intervals between positions (group B). The primary outcome measure was the ratio of maximum slow-phase eye velocity (MSPEV) of positional nystagmus soon after the EM, compared with that measured before the EM. Secondary outcome included whether a 30 min interval after the EM enabled recovery of MSPEV of positional nystagmus to the original value. This study followed the CONSORT 2010 reporting standards.Results: In both groups A and B, the immediate effect of the EM could be observed, because MSPEV during the second Dix-Hallpike test was significantly smaller than MSPEV during the first Dix-Hallpike test (p < 0.0001 in group A, p < 0.0001 in group B). The primary outcome measure was larger in group B than in group A (p = 0.0029). The immediate effect faded 30 min later (secondary outcome).Conclusions: This study showed that the EM had an immediate effect both with and without interval time in each head position of the EM. Because setting interval time in each head position of the EM reduced the immediate effect of the EM, interval time during the EM adds less benefit. This finding can reduce the effort exerted by doctors, as well as the discomfort experienced by patients with pc-BPPV, during EM. However, this immediate effect may be caused by BPPV fatigue, and may fade rapidly.Classification of Evidence: 1b

Direction-Changing and Direction-Fixed Positional Nystagmus in Patients With Vestibular Neuritis and Meniere Disease.

ObjectivesDirection-changing positional nystagmus (PN) was considered to indicate the presence of benign paroxysmal positional vertigo involving lateral semicircular canal in most cases. We investigated the incidence of PN on the supine head-roll test and compared the characteristics of nystagmus in patients with vestibular neuritis (VN) and Meniere disease (MD).MethodsA retrospective review of patients, who were diagnosed with unilateral VN or unilateral definite MD between September 2005 and November 2011, was conducted. Sixty-five VN patients and 65 MD patients were enrolled. Eye movements were recorded for 30–60 seconds at the positions of sitting, head roll to the right, and head roll to the left, and maximum slow-phase eye velocity was calculated. PN was classified as direction-fixed (paretic or recovery) and direction-changing (geotropic or apogeotropic).ResultsSpontaneous nystagmus was observed in 57 patients (87%, the slow-phase eye velocity of 7°/sec±5°/sec) with acute VN, 39 (60%, 2°/sec±1°/sec) with follow-up VN, and 32 (49%, 2°/sec±2°/sec) with MD. Direction-fixed PN was the most common type. Direction-fixed paretic type was most common in acute VN (80%) and follow-up VN (42%), and direction-fixed recovery type was most common in MD (31%). Paretic type was significantly more common in acute VN (80%) than in follow-up VN (42%) and MD (26%), and the recovery type was significantly more common in MD (31%) than in acute VN (3%) and follow-up VN (14%). Direction-changing PN was more common in MD (22%), followed by follow-up VN (14%) and acute VN (9%).ConclusionThough direction-fixed paretic PN was most common in VN and MD patients, direction-changing PN could be observed in a few patients (9%–20%) with peripheral vestibular disorders regardless of the duration from the onset of dizziness, suggesting the presence of otolith-related dizziness.

Recovery of positional nystagmus after benign paroxysmal positional vertigo fatigue.

In benign paroxysmal positional vertigo (BPPV), positional nystagmus is generally weaker when the Dix-Hallpike test is repeated. This phenomenon is known as BPPV fatigue. The positional nystagmus induced by the Dix-Hallpike test can be observed again when time has passed. There has been no study regarding the length of time required to recover the positional nystagmus. The purpose of this study was to examine whether positional nystagmus recovers within 30min after the disappearance of the nystagmus by BPPV fatigue. This was a prospective observational study. Twenty patients with posterior canal type of BPPV (canalolithiasis of the posterior canal) were included. Dix-Hallpike tests were performed three times for each patient. A second Dix-Hallpike test was performed immediately after the first Dix-Hallpike test. A third Dix-Hallpike test was performed 30min after the second Dix-Hallpike test. We recorded positional nystagmus induced by the Dix-Hallpike tests and analyzed maximum slow-phase eye velocity (SPEV) of the positional nystagmus. The average maximum SPEV of positional nystagmus induced by the second Dix-Hallpike test (4.8°/s) was statistically lower than that induced by the first Dix-Hallpike test (48.0°/s); this decrease was caused by BPPV fatigue. There was no statistical difference between average maximum SPEV of positional nystagmus induced by the first Dix-Hallpike test and that induced by the third Dix-Hallpike test (41.6°/s); this indicates that the effect of BPPV fatigue disappeared. The effect of BPPV fatigue disappears within 30min. A second Dix-Hallpike test should be performed at least 30min after the first.

Velocity storage mechanism in zebrafish larvae

The optokinetic reflex (OKR) and the angular vestibulo-ocular reflex (aVOR) complement each other to stabilize images on the retina despite self- or world motion, a joint mechanism that is critical for effective vision. It is currently hypothesized that signals from both systems integrate, in a mathematical sense, in a network of neurons operating as a velocity storage mechanism (VSM). When exposed to a rotating visual surround, subjects display the OKR, slow following eye movements frequently interrupted by fast resetting eye movements. Subsequent to light-off during optokinetic stimulation, eye movements do not stop abruptly, but decay slowly, a phenomenon referred to as the optokinetic after-response (OKAR). The OKAR is most likely generated by the VSM. In this study, we observed the OKAR in developing larval zebrafish before the horizontal aVOR emerged. Our results suggest that the VSM develops prior to and without the need for a functional aVOR. It may be critical to ocular motor control in early development as it increases the efficiency of the OKR.

Effects of endolymphatic sac decompression surgery on endolymphatic hydrops

Conclusions: The present findings suggest that complete control of vertigo after endolymphatic sac decompression surgery (ESDS) does not always depend on improved vestibular function or reduced endolymphatic hydrops. Vertigo control is, however, associated with hearing stability.Objective: Among surgical treatments for intractable Meniere’s disease, ESDS is performed to preserve and improve inner ear function. We examined the correlation between changes in vertigo frequency and neuro-otologic function to understand the condition of the inner ear in patients whose vertigo was completely controlled after undergoing ESDS.Methods: This was a retrospective cross-tabulation study. Between 1997 and 2001, we treated 52 patients with intractable vertigo using ESDS and followed the patients regularly for 2 years. Postoperatively we evaluated and recorded changes in vertigo attack frequency, maximum slow phase eye velocity, worst hearing level, and glycerol test results according to modified American Academy of Otolaryngology–Head and Neck Surgery 1995 criteria.Results: We found no correlation between vertigo control and vestibular function. There was also no correlation between vertigo control and negative conversion of the glycerol test. There was a significant correlation between vertigo control and hearing control .

Hyperventilation-Induced Nystagmus in Patients with Vestibular Neuritis in the Acute and Follow-Up Stages

Objective: Our purposes were to characterize hyperventilation-induced nystagmus (HVIN) in patients with unilateral vestibular neuritis (VN) through follow-up examinations and to determine the effects of hyperventilation on vestibular imbalance in patients with VN. Materials and Methods: The horizontal eye movements in 35 patients with acute VN were recorded. The eye movements were analyzed and the maximum value of slow-phase eye velocity (SPV) was obtained during and after hyperventilation. Nineteen of 35 patients underwent follow-up examinations around 7 weeks later. When spontaneous nystagmus was present, the SPV of spontaneous nystagmus was subtracted from that of HVIN. A maximum SPV of HVIN of ≧4°/s was considered abnormal. The direction and SPV of HVIN were analyzed. Results: The incidence of HVIN in patients with VN was significantly higher in the acute stage (18 of 35; 51%) than the follow-up stage (4 of 19; 21%). The direction of HVIN present in the follow-up stage was entirely towards the contralesional side (contralesional HVIN). However, the direction of HVIN in the acute stage was mixed, towards the contralesional side (10 of 35; 28%) and towards the ipsilesional side (8 of 35; 23%). The SPVs (49 ± 56°/s) of ipsilesional HVIN were significantly greater than the contralesional HVIN in the acute stage (8 ± 3°/s). Robust nystagmus (SPV ≧25°/s) was entirely ipsilesional HVIN, which was observed only in the acute stage. Conclusions: Our findings indicate that hyperventilation can result in aggravation of vestibular imbalance in the acute and follow-up stages in different ways. Hyperventilation resulted in contralesional HVIN in both the acute and follow-up stages, each in approximately a fourth of the patients, which suggests a disruption of central static compensatory mechanisms. However, ipsilesional HVIN was elicited only in the acute stage (in approximately a fourth of the patients). About half of the patients with ipsilesional HVIN showed robust responses, which is a characteristic finding, suggesting a transient intense increase in vestibular activity on the lesional side.

Changes in caloric responses after temporal bone surgery with posterior tympanotomy

Objective To elucidate the role of facial recess bony plate in the thermal transmission route from external auditory canal to lateral semicircular canal during caloric stimulation test, we performed the test on patients before and after removal of the plate, i.e. posterior tympanotomy. In the present study, we adopted facial nerve decompression (FND) as posterior tympanotomy without surgery-induced inner ear damages and cochlear implantation (CI) as posterior tympanotomy with surgery-induced inner ear damages. Methods Between 1999 and 2003, we performed FND on 19 patients with unilateral facial nerve paresis due to Bell’s palsy ( n = 7), Ramsay-Hunt syndrome ( n = 7) or facial nerve trauma ( n = 5) at Osaka Rosai Hospital. We also performed CI on 34 patients with bilateral deafness at Osaka University Hospital. To examine effects of FND or CI on caloric responses in vestibular periphery, caloric stimulation (30 °C cold water and 44 °C hot water) with ENG was performed twice, just before and 6 months after surgery in each subject. The caloric-induced nystagmus was recorded by using ENG under dark and open-eyes situation to calculate the maximum slow phase eye velocity. Results In cases of FND ( n = 19), there were significant decreases between pre- and post-operative 30 °C responses ( t-test: p = 0.049 < 0.05). There were no significant differences between pre- and post-operative 44 °C responses ( t-test: p = 0.467 > 0.05). In cases of CI ( n = 34), there were significant changes between pre and post-operative responses in both temperatures ( t-test: p < 0.0001 in 30 °C; p = 0.011 < 0.05 in 44 °C). Conclusion The insertion of electrodes during CI did some damages to vestibular peripheral function and reduced both hot and cold caloric responses according to the results of CI. However, the procedure during posterior tympanotomy could also decrease caloric responses especially in cold stimulation according to the results of FND. Therefore, we should consider the effect of structural change in temporal bone on the thermal transmission in case of evaluation of vestibular peripheral function by using caloric stimulation test.

前庭神経炎症例における健側耳の温度眼振反応の検討

We studied caloric responses of the unaffected side of patients with vestibular neuritis (VN). Six patients with VN, who underwent sequential caloric tests, were enrolled in this study. In all 6 subjects, the maximum slow phase eye velocity of caloric nystagmus on the unaffected side to ice water was smaller at the earlier stage after the vertigo attack (within one month after the attack) than that at the later stage. This phenomenon might be associated with the suppression of contralateral vestibular nuclei, which would be a part of vestibular compensation. We should take into consideration that caloric responses on the unaffected side could be altered according to the stage of the disease.

Functional significance of peripheral head-shaking nystagmus.

The objective was to determine the characteristics of horizontal head-shaking nystagmus of peripheral origin and its relationship to vestibular dysfunction. Retrospective case series. Eighty-three patients met the inclusion criteria of having peripheral and unilateral vestibular disease. Patients were tested with video nystagmography. Head-shaking nystagmus was performed in the horizontal plane during 30 cycles at a frequency of approximately 3 Hz. Head-shaking nystagmus was classified as monophasic or biphasic and, based on the pathological ear, as ipsilateral or contralateral related to nystagmus fast phases. The two-tailed t test, ANOVA, Mann-Whitney and chi2 tests, and lineal and polynomial regression tests were used for statistical analysis. Twenty-three patients showed a positive head-shaking nystagmus. All cases of head-shaking nystagmus observed were horizontal. There were four biphasic and 19 monophasic cases of head-shaking nystagmus. First phases of biphasic head-shaking nystagmus beat toward the normal ear. Eleven of the monophasic cases of head-shaking nystagmus were ipsilateral, and nine were contralateral. There was a statistically significant correlation between caloric weakness and head-shaking nystagmus. Ipsilateral head-shaking nystagmus corresponded to lower caloric asymmetries, and contralateral and biphasic head-shaking nystagmus corresponded to greater caloric weakness (P <.001). As the caloric asymmetry increased, the maximal slow-phase eye velocity of head-shaking nystagmus was greater (P =.01) and its duration shortened (P =.008). Ipsilateral responses could be distinguished from contralateral responses based on their latency (P =.03), maximal slow-phase eye velocity (P <.05), and duration (P =.02). The frequency of head-shaking nystagmus was significantly higher among older patients. There was no correlation between head-shaking nystagmus and clinical patterns. Head-shaking nystagmus of peripheral vestibular origin is a response both qualitatively and quantitatively associated with the degree of the vestibular loss.

A new rotational test for vertical semicircular canal function

Objective: We developed a new rotating chair in order to assess the function of the vertical semicircular canal (VSCC) by analyzing VSCC-induced post-rotatory nystagmus (PRN). Methods: We examined 14 healthy subjects, wearing goggles equipped with an infrared CCD camera, and sitting on a chair which was designed to stimulate a pair of the VSCCs by tilting the head 60° backward with a 45° rotation to the left or right side from the sagital plane. The time constant (TC) or maximal slow phase eye velocity (MSPEV) of the vertical component of four kinds of PRN were analyzed in four corresponding rotatory conditions, and used as functional index of the corresponding VSCC. Results: The mean values of MSPEV in both anterior semicircular canal (ASCC) and posterior semicircular canal (PSCC)-induced PRN tended to be lower ( P<0.10) than those induced by the lateral semicircular canal (LSCC). The result suggests that the threshold to the angular velocity in the VSCC is lower than that in the LSCC. The mean values of TC in both ASCC and PSCC-induced PRN were significantly lower ( P<0.05) than those induced by the LSCC. Conclusion: The significant reduction of TC in VSCC-induced PRN compared with LSCC-induced PRN indicates that VSCC function is less affected by velocity storage mechanisms than LSCC function. The rotational test with respect to the VSCC can be used as a tool for assessing vertical canal function.

Vertical Semicircular Canal Function: A Study in Patients with Benign Paroxysmal Positional Vertigo

A pendular rotation test in a head-tilted position (60° backwards and rotated 45° to either the right or left) was performed in 7 patients with benign paroxysmal positional vertigo (BPPV). Patients were rotated 360° at a frequency of 0.1 Hz (maximum speed 114°/s). The excitability of vertical semicircular canals was evaluated using this test procedure. Using an infrared CCD camera and a PC, evoked nystagmus was analyzed in order to determine the morbidity of BPPV. A statistically significant difference ( p <0.05) was found in the maximal slow-phase eye velocity between nystagmus from the anterior semicircular canal and nystagmus from the posterior semicircular canal. The excitability of the posterior semicircular canal in the affected ear was lower than that of the anterior semicircular canal. However, when vertigo and nystagmus disappeared, the difference in excitability was improved. The present results indicate some functional deterioration of the posterior semicircular canal in BPPV cases, suggesting the participation of both mechanical (dumping by mass) and organic (peripheral end organ) factors in causing morbidity.

Self-Perceived Balance Disability/Handicap in the Presence of Bilateral Peripheral Vestibular System Impairment

The purpose of this report was to characterize the self-perceived balance disability/handicap of patients with bilateral reductions and bilateral complete losses of peripheral vestibular system function. Data from 72 patients whose electronystagmography and rotational examinations suggested normal, unilateral, or bilateral reductions in peripheral vestibular system function were used in the first investigation. Patients also completed a Dizziness Handicap Inventory (DHI). Results demonstrated significant group differences for DHI total and physical subscale scores. There were significant differences between normal and bilateral weakness groups for the total DHI score and between normal and unilateral and normal and bilateral weakness groups for the physical subscale score. In a second investigation, an item analysis of the DHI is presented for five patients with bilateral complete losses of peripheral vestibular system function. Results show that, predictably, these patients have difficulty engaging in activities requiring an intact vestibulocular reflex (e.g., physical activities such as sports, household chores).

簡易温度刺激検査の再検討 Ａｉｒ ｃａｌｏｒｉｃ刺激装置を用いて

The simple cold caloric test (20°C, 5 ml water irrigation for 10 sec. and stimulation for 20 sec.) is an established method of investigating right and left vestibular function separately. In addition, this test should decrease examination time and patient's discomfort.The caloric response in this test is considered to be normal when the maximal slow phase eye velocity (MSV) is not less than 20°/sec.. We have used the simple caloric test as one of the routine vestibular function tests.As stimulation, air irrigation (15°C, 61/min., 60 sec.) is used instead of water irrigation.We have experienced that the MSV in both ears equally showed less than 20°/sec., or a large difference although each ear revealed normal caloric response.Therefore, we reexamined the simple cold caloric test for 24 normal volunteers. The purpose of the study was to investigate in normal subjects whether the MSV of both ears was equal or a normal caloric response was obtained. The results were follows, 1) MSV not less than 20°/sec. was demonstrated in 83% of normal volunteers. 2) The MSV in these subjects ranged from 9°/sec. (minimum) to 50°/sec. (maximum). 3) There was good correlation between the right and left MSV (mean±2SD). It is concluded that, in the response to simple cold caloric test, there are individual differences but not very much difference between the right and left ear of the same individual.

Study of optokinetic nystagmus and spino-motor functions with cyclo-rotatory optokinetic stimulus

It has been shown that the neural channels from the otolith organs and the vertical semicircular canals connect to the cyclo-rotatory oculomotor system. However, only a few studies have been conducted to examine the relationship between the cyclo-rotatory optokinetic (COK) and the vestibular inputs. Accordingly, we have analyzed the cyclo-rotatory oculomotor output evoked by a COK stimulus, in 30 subjects; 21 normal adults, 4 elderly persons, and 5 persons with unilateral vestibular dysfunction. In addition, the spinal motor output was simultaneously recorded and comparatively analyzed. The increase in COK nystagmus (COKN) was less than that in horizontal and vertical OKN. There was a significant decline in the maximum slow phase eye velocity in the elderly subjects as well as in the subjects with unilateral vestibular dysfunction, compared to that in the normal adult subjects. Regarding the spinal motor output, in the subjects with unilateral vestibular dysfunction, a pronouned increase in the sway distance from the center of gravity was found with COK stimulus forward the lesioned side. However, with the COK stimulus, there was no significant correlation between the output functions of the cyclorotatory oculomotor system and those of the spinal motor system.

垂直半規管の回転検査 頭位別の眼球運動解析

Benign Paroxysmal positioning vertigo and acoustic tumors are thought to be related to the function of the vertical semicircular canal (VSCC). Therefore, we developed a new test to assess VSCC function by analyzing VSCC-induced nystagmus. We examined 11 healthy subjects, wearing goggles equipped with an infrared CCD camera and sitting on a chair designed to bilaterally stimulate the VSCCs by tilting the head backward during 45° rotation to the right on the sagital plane. The stimuli used were sinusoidal rotation with a maximal angular velocity of 100°/sec at a frequency of 0.033 Hz. The result was that the maximum slow phase eye velocity (MSPEV) of horizontal nystagmus decreased parallel to the head-tilted angle and the MSPEV of the vertical nystagmus was maximal when the head was tilted 60° or 70° backward. From the perspective of VSCC anatomy, the direction of horizontal nystagmus is reversed when head is tilted 60° backward. However, we could not observe the reverse of the direction of horizontal nystagmus even when head tilted 80° backward. We considered that vertical nystagmus was maximal when the head was tilted 60-70° backward because this position applied the optimal stimulation to the VSCC. This finding is in agreement with the position of the vertical VSCC in skull. We concluded that rotational test with respect to the VSCC can be used to analyze VSCC function.

Correlation between the age-dependent changes in caloric response and in pure tone hearing

Previous reports have examined the age-dependent changes of the auditory system or the caloric response, but results have been inconsistent. No study to date has correlated the age-dependent changes in caloric response with those in pure tone hearing in the same subjects. In this study a caloric test and a pure tone audiometry test were performed in 86 subjects (172 ears), age range 24 to 84 years of age, including 12 otoneurologically healthy volunteers (24 ears), and 74 tinnitus patients without subjective hearing loss (148 ears). The maximal slow phase eye velocity (SPEV) of caloric nystagmus response and the mean hearing level at high frequencies were measured and the age-dependent changes in these scores were compared. The following results were obtained. 1) The SPEV of caloric nystagmus, which remained unchanged until markedly advanced age, decreased significantly from 65 years of age in men and from 75 years in women; the change occurring earlier in men than in women. 2) The hearing level at high frequencies decreased abruptly from 50 years of age with a more gradual change from 75 years was significantly lower in men than in women over 65 years of age. 3) There was a weak but significant correlation between the age-dependent changes in SPEV and those in hearing level at high frequencies.