Abnormal deviation of subjective visual horizontal in patients with vestibular schwannoma

OBJECTIVES: This study was aimed to examine the correlation between the results of subjective visual horizontal (SVH) and other vestibular function tests in patients with untreated unilateral vestibular schwannoma (VS). METHODS: The subjects comprised 40 consecutive patients (17 men, 23 women) with VS who underwent vestibular function tests before surgery and had surgically and histopathologically confirmed unilateral VS. The vestibular function tests included SVH, caloric, and vestibular evoked myogenic potential (VEMP) tests. RESULTS: Of the 40 patients, 31 (77.5%) showed deviation of the SVH toward the affected side down. Especially in 8 patients (20.0%), abnormal deviation (more than 2.2 degrees) toward the affected side down was seen. None of the patients showed abnormal deviation toward the unaffected side down. On the caloric test, the proportion of absent caloric responses and the percent canal paresis in patients with an abnormal SVH was significantly higher than those in patients with a normal SVH. The proportion of abnormal VEMP responses was higher and the percent VEMP asymmetry was smaller in patients with an abnormal SVH than in patients with a normal SVH; however, the differences were not significant. CONCLUSIONS: Abnormal results on the caloric test and/or VEMP test were more frequently seen in VS patients with abnormal deviation of the SVH.     

Idiosyncratic compensation of the subjective visual horizontal and vertical in 60 patients after unilateral vestibular deafferentation

OBJECTIVE: To investigate long-term compensation mechanisms of utricular function after translabyrinthine surgery for vestibular schwannoma. Correlations between the subjective visual horizontal (SVH) and subjective visual vertical (SVV) and other parameters of vestibular compensation were studied. The correlation between the SVH and SVV was also investigated to see whether these measurements are compatible for patients. MATERIAL AND METHODS: Sixty consecutive patients were investigated 3 months before and 6 months after surgery by means of electronystagmography and SVH and SVV tests. Tumor size was measured using MRI. RESULTS: The SVH and SVV increased significantly towards the ipsilesional side postoperatively. Preoperative tilt correlated with age. Postoperative tilt correlated weakly with preoperative caloric sensitivity and inversely with tumor size. The correlation between the SVH and SVV was high both before and after surgery (r(s) > 0.74; p < 0.001). CONCLUSIONS: The long-term compensation of static tilt perception was dependent on age and not on dynamic canal functions. We propose an idiosyncrasy in the SVH and SVV compensation after unilateral vestibular deafferentation, incongruous with the general course of vestibular compensation. The results suggest a probable dependence on non-vestibular information, i.e. proprioception, in facilitating compensation of static vestibular deficits. The similarity between the SVH and SVV measurements confirms that either test can be used clinically for patients with vestibular lesions.     

Clinical use of subjective visual horizontal and vertical in patients of unilateral vestibular neuritis.

OBJECTIVES: Subjective visual horizontal (SVH) and subjective visual vertical (SVV) used to assess otolith dysfunction and ipsilesional deviation of SVV and SVH in unilateral vestibular dysfunction is well known. The goal of this study was to investigate the clinical use of SVH/SVV and a dizziness scale in the clinical setting of acute unilateral vestibular neuritis. METHODS: Thirty-five patients with unilateral vestibular neuritis were investigated. Every patient was diagnosed by physical examination and electronystagmography. Subjective visual horizontal and SVV were assessed during the acute or subacute period; the Dizziness Handicap Inventory (DHI) and Vestibular Disorder Activities of Daily Living Scale (VADL) were used for a self-dizziness scale at the same time. All patients underwent rehabilitation therapy. Subjective visual horizontal/SVV and DHI/VADL were assessed again approximately 4 weeks later. Postrehabilitation SVH/SVV and DHI/VADL data were compared with initial data. RESULTS: Dizziness Handicap Inventory and VADL were improved after 4 weeks of rehabilitation, and the deviation toward ipsilesional side SVH and SVV was also improved. CONCLUSION: These results demonstrate that SVH and SVV correlated with clinical dizziness symptoms in patients with acute unilateral vestibular neuritis. Therefore, SVH and SVV would be useful tools for the evaluation of clinical manifestations of unilateral vestibular neuritis.     

Idiosyncratic compensation of the subjective visual horizontal and vertical in 60 patients after unilateral vestibular deafferentation

Objective To investigate long-term compensation mechanisms of utricular function after translabyrinthine surgery for vestibular schwannoma. Correlations between the subjective visual horizontal (SVH) and subjective visual vertical (SVV) and other parameters of vestibular compensation were studied. The correlation between the SVH and SVV was also investigated to see whether these measurements are compatible for patients.

Material and Methods Sixty consecutive patients were investigated 3 months before and 6 months after surgery by means of electronystagmography and SVH and SVV tests. Tumor size was measured using MRI.

Results The SVH and SVV increased significantly towards the ipsilesional side postoperatively. Preoperative tilt correlated with age. Postoperative tilt correlated weakly with preoperative caloric sensitivity and inversely with tumor size. The correlation between the SVH and SVV was high both before and after surgery (r_s>0.74; p<0.001).

Conclusions The long-term compensation of static tilt perception was dependent on age and not on dynamic canal functions. We propose an idiosyncrasy in the SVH and SVV compensation after unilateral vestibular deafferentation, incongruous with the general course of vestibular compensation. The results suggest a probable dependence on non-vestibular information, i.e. proprioception, in facilitating compensation of static vestibular deficits. The similarity between the SVH and SVV measurements confirms that either test can be used clinically for patients with vestibular lesions.     

Does acute dysfunction of the saccular afferents affect the subjective visual horizontal in patients with vestibular neurolabyrinthitis?

CONCLUSIONS: The results of a series of studies including the present study suggest that acute dysfunction of the utricular afferents accompanied by acute dysfunction of the saccular afferents might require more time for the compensation of the otolith-ocular system than acute utricular dysfunction that was not accompanied by acute saccular dysfunction. Perhaps the inputs from the saccule also have some contribution to the subjective visual horizontal (SVH). OBJECTIVE: To clarify if acute dysfunction of the saccular afferents affects the SVH. PATIENTS AND METHODS: Twenty-six patients with vestibular neurolabyrinthitis (20 men and 6 women, 23-67 years of age) were enrolled in this study. They had undergone measurement of SVH at the early stage (within 1 month after the attack) and 3 months after the attack. For the measurement of SVH, we used a device that has a red bar of light-emitting diodes with a head fixing frame. They also underwent vestibular evoked myogenic potentials (VEMPs) testing. For the recording of VEMPs, 95 dBnHL clicks were presented. RESULTS: Patients with vestibular neurolabyrinthitis showed deviation of SVH toward the affected side-down at the early stage after the attack, irrespective of VEMP results. However, 3 months after the attack SVH was significantly more deviated toward the affected side-down in patients who showed absent VEMPs than those with VEMPs present (p<0.01 Mann-Whitney U test).     

Long-lasting deviation of the subjective visual horizontal after complete unilateral vestibular deafferentation by subtotal resection of the temporal bone.

OBJECTIVE: This study examined whether subjective visual horizontal (SVH) could be compensated in patients with complete loss of unilateral vestibular function. PATIENTS: Patients comprised two men and three women who underwent subtotal resection of the unilateral temporal bone due to squamous cell carcinoma of the middle or external ear. Mean patient age was 63.2 years (range, 59-69 yr). INTERVENTION: Diagnostic. MAIN OUTCOME MEASURES: Patients were tested postoperatively (mean, 4 yr 5 mo after the surgery; range, 2 yr 9 mo to 8 yr 6 mo). The task for patients involved adjusting a laser projection bar four times to SVH in darkness. RESULTS: All patients displayed marked deviation of SVH toward the operated side-down. Mean deviation from four trials for each subject was 4.5, 2.9, 3.7, 3.0, and 3.4 degrees. CONCLUSION: Deviation of SVH in patients with definite unilateral vestibular deafferentation can be long term, lasting more than 2 years at least.     

Vibration-induced shift of the subjective visual horizontal: a sign of unilateral vestibular deficit.

BACKGROUND: Vibration to the head or neck excites vestibular and neck muscle spindle afferents. Can such vibrations improve the sensitivity of the subjective visual horizontal (SVH) test to chronic unilateral deficit of the vestibular system? DESIGN: Controlled experimental study. SETTING: Tertiary referral center. PATIENTS AND CONTROLS: Thirteen healthy subjects and 23 patients with chronic unilateral vestibular deficits after vestibular neurectomy or neurolabyrinthitis. Results of head-impulse test showed unilateral loss of function of all 3 semicircular canals in 14 patients and loss of anterior and lateral semicircular canals in 9 patients. INTERVENTION: Unilateral vibration (92 Hz; 0.6-mm amplitude) applied to sternocleidomastoid muscle (SCM) or mastoid bone. MAIN OUTCOME MEASURE: Results of SVH test (in degrees). RESULTS: Without vibration, 13 of 23 patients and all healthy subjects had SVH of less than 3 degrees (sensitivity, 43%; specificity, 100%). During vibration to the ipsilesional SCM, SVH increased to greater than 3 degrees in 21 of 23 patients but in only 1 of 13 healthy subjects (sensitivity, 91%; specificity, 92%). The patient group had significantly greater SVH shifts to the ipsilesional side than did healthy subjects in response to SCM and mastoid bone vibration on either side. The SVH shift during vibration to the ipsilesional SCM was significantly greater than that during vibration to the contralesional muscle (P<.001) or to the mastoid bone on either side (P<.05). The vibration-induced SVH shift was significantly greater in those patients with loss of 3 semicircular canals than in those with loss of 2 (P<.01). CONCLUSIONS: The sensitivity of the SVH test to chronic unilateral vestibular deficits can be improved by applying vibration to the SCM. The magnitude of vibratory SVH shift is related to the extent of unilateral deficit of the otolithic organs, vertical canals, or both.     

主观视觉水平线在单侧前庭周围性病变中的应用研究

目的 探讨外周单侧前庭功能减退患者的主观视觉水平线特点及其对前庭功能评定的临床价值.方法 分别对85例外周单侧前庭功能减退患者及39名健康对照组人群行主观视觉水平线、主观视觉垂直线及冷热试验等前庭功能检测,以主观视觉水平线及主观视觉垂直线偏斜角度、冷热试验优势偏向(directional preponderance,DP)值、单侧半规管轻瘫(unilateral weakness,UW)值为参数,分析总结外周单侧前庭功能减退患者的主观视觉水平线特点,主观视觉水平线、主观视觉垂直线之间及其分别与DP、UW值、病程的相关性.以SPSS 16.0软件对数据进行统计学分析.结果 健康对照组主观视觉水平线、主观视觉垂直线的偏斜角度为-2,～2.以此为判定阳性与阴性的标准.外周单侧前庭功能减退患者的主观视觉水平线、主观视觉垂直线阳性者分别为46例(54.1%)、43例(50.6%),二者比较差异无统计学意义(χ2=12.5,P=0.481);DP阳性者55例(64.7%),与主观视觉水平线、主观视觉垂直线比较,差异均无统计学意义(χ2值分别为0.19、2.86,JP值分别为0.164、0.067).外周单侧前庭功能减退患者的主观视觉水平线与主观视觉垂直线偏斜角度呈正相关(r=0.939,P<0.01),且二者与DP值均呈正相关(r值分别为0.648、0.658,P值均<0.05),与UW值无相关性(r值分别为0.048、0.085,P值均>0.05).根据主观视觉水平线或主观视觉垂直线、DP、UW3个参数的阳性或阴性组合,可分别构成3种主要结果形式,即:主观视觉水平线(+)DP(+)UW(+),主观视觉水平线(-)DP(+)UW(+),主观视觉水平线(-)DP(-)UW(+);主观视觉垂直线(+)DP(+)UW(+),主观视觉垂直线(-)DP(+)UW(+),主观视觉垂直线(-)DP(-)UW(+).以上6种形式的病程中位数分别为5.0、10.0、15.0 d,5.0、9.5、14.5 d,分别行多样本秩和检验,差异均有统计学意义(χ2水平线:8.80,P=0.012;χ2垂直线=6.26,P=0.040).结论 主观视觉水平线可以评估耳石器(椭圆囊)功能.外周单侧前庭功能减退患者的主观视觉水平线、主观视觉垂直线偏斜角度随病程和前庭代偿进程呈动态变化,可用于前庭静态代偿评定.

Abstract：

Objective To analyze the characteristics of subjective visual horizontal ( SVH) and evaluate its clinical value for vestibular function in peripheral unilateral vestibular hypofunction ( UVH). Methods Eighty-five patients with UVH (study group) and 39 normal persons (control group) accepted vestibular function tests, including SVH, subjective visual vertical ( SVV ) and caloric test by video-nystagmography. The parameters of the angle of SVH and SVV, directional preponderance ( DP) and unilateral weakness(UW) of caloric test were observed. The correlation between SVH/SVV, DP, UW and the course of disease were investigated respectively. SPSS 16. 0 software was used to analyze the data. Results Reference range of SVH and SVV was from - 2° to 2° in the control group. Among the 85 patients, 46 cases(54. 1% ) and 43 cases(50. 6% ) had the abnormal values of SVH and SVV respectively, with no statistical significance( χ2 = 12. 5, P = 0. 481 ) by chi square test Fifty-five cases (64. 7% ) withabnormal DP had no statistical significance when compared with SVH and SVV respectively (χ2 values were 0. 19 and 2.86, respectively, P value were 0. 164, 0.067, respectively). In UVH, there were positive correlation between SVH, SVV and DP( r value was 0. 939, 0. 648, 0. 658, all P <0. 05) respectively, but no correlation between UW and SV H or SVV (r value was 0. 048, 0. 085, all P > 0. 05). According to the permutation and combination of the four parameters, positive or negative, three main groups could be defined [SVH(+)DP(+)UW( +), SVH( -)DP( +)UW( +), SVH( -)DP( -)UW( +); SVV( + ) DP ( +)UW( +), SVV( -)DP( +)UW( +), SVV( -)DP( -)UW( +)]. The course of disease in the three main groups was positively skewed distribution,with median of 5. 0, 10. 0, 15. 0 d and 5. 0, 9. 5, 14. 5 d respectively. By Kruskal-Wallis Test, χ2 value were 8. 80 and 6. 26, respectively( P value were 0.012, 0. 040, respectively), with statistical significance between the above three main groups. Conclusions The SVH value can evaluate the function of the otolithic. The angle of SVH and SVV are changing in the course of disease, SVH and SVV can be used as a guidance of the vestibular compensation evaluation.     

全聋型突发性耳聋患者的预后与前庭症状及前庭功能关系的回顾性分析

目的 探讨全聋型突发性耳聋患者的预后与前庭症状及前庭功能的关系。 方法 回顾性分析52例单侧全聋型突发性耳聋患者的前庭症状,以及眼肌前庭诱发肌源性电位(oVEMP)、颈肌前庭诱发肌源性电位(cVEMP)、视频头脉冲试验(vHIT)和冷热试验结果,观察这些患者的听力结果与前庭症状及前庭功能的关系。 结果 在52例单侧全聋型突发性耳聋患者中,有前庭症状、前庭功能异常的全聋型患者与无前庭症状者、功能正常者相比疗效差异有统计学意义。oVEMP、cVEMP、vHIT和冷热试验四项结果异常的全聋型患者显示出更低的治疗总有效率,oVEMP、cVEMP、vHIT和冷热试验正常的突发性耳聋患者有更高的听力恢复数值。 结论 有前庭症状、前庭功能异常的全聋型突发性耳聋患者疗效较差,oVEMP、cVEMP、vHIT和冷热试验正常的全聋型突发性耳聋患者有更好的听力恢复。前庭功能异常提示突发性聋患者的内耳病变范围较大、程度较重。     

Subjective Visual Horizontal During Follow-up After Unilateral Vestibular Deafferentation with Gentamicin

The subjective visual horizontal (SVH) was measured by means of a small, rotatable, luminous line in darkness in the upright head and body position and at 10, 20 and 30° of tilt to the right and left before, and repeatedly during a follow-up period of 1 year after intratympanic gentamicin instillations in 12 patients with recurrent vertigo attacks. This treatment caused a loss of the bithermal caloric responses on the diseased side. Shortly after treatment there was a significant tilt of SVH towards the treated side (group mean=10.6°). Repeated testing made it possible to characterize mathematically the changes with time for SVH. For the group of patients as a whole this otolithic component of vestibular compensation was best described by a power function, SVH=8.65t^-0.16 degrees, where t is time in days after maximum tilt of SVH. After 1 year, SVH was still significantly tilted towards the treated side (group mean=3.16°). Gentamicin treatment also caused a significant reduction in the perception of head and body tilt towards the deafferented side, while the perception of tilt towards the healthy side did not show any significant changes. During follow-up there was a gradual improvement in the perception of tilt towards the treated side. However, a significant asymmetry in roll-tilt perception was still present 1 year after deafferentation. There was no correlation between SVH in the upright position and roll-tilt perception, suggesting that these parameters are to some extent dependent on different afferent input from the vestibular organ. They were also found to be complementary for the detection of vestibular disturbance.     

前庭神经炎患者虚拟现实辅助主观垂直水平视觉研究

目的 通过观察前庭神经炎患者主观垂直、水平视觉测试结果,为临床诊断提供依据.方法 45名无眩晕的健康自愿者作为健康对照组,46名单侧前庭神经炎患者作为VN组,均佩戴VR眼镜,分别完成头正中位的主观垂直视觉和主观水平视觉试验.结果 健康对照组主观视觉水平线、主观视觉垂直线的偏斜角度为-2°～2°.以此为判定阳性与阴性的标...     

Relation of video-head-impulse test and caloric irrigation: a study on the recovery in unilateral vestibular neuritis

The head-impulse test (HIT) is an important test for examining unilateral vestibular hypofunction. The new video-head-impulse test (vHIT) is more sensitive and specific than the clinical bedside-head-impulse test. Alternatively, one can test for vestibular hypofunction with the caloric irrigation test. Various studies have shown that both tests may not always identify vestibular hypofunction; instead, the results of the tests might be contradictory. To further explore the question, of whether vHIT and caloric irrigation test the same part of the angular horizontal vestibulo-ocular reflex (VOR), we examined patients with unilateral vestibular neuritis at different points in time. The tonic vestibular imbalance (e.g., subjective-visual-vertical, ocular torsion and spontaneous nystagmus) and dynamic dysfunction of VOR (vHIT and bithermal caloric irrigation) were measured and quantified. While parameters of the tonic vestibular imbalance were well described by single exponential decay functions, dynamic parameters were less well defined. Therefore, to better compare the time course of pairs of two different parameters, we used a linear regression analysis. No linear correlation was found in the group and individually for the gain asymmetry and the ipsilesional gain of the vHIT with the unilateral weakness of the bithermal caloric irrigation tests. Linear correlation was found for most parameters of tonic vestibular imbalance. These findings are further evidence that vHIT and caloric irrigation test different parts of the angular VOR.     

Subjective visual horizontal in patients with posterior canal benign paroxysmal positional vertigo

CONCLUSION: Patients with posterior canal benign paroxysmal positional vertigo (p-BPPV) could have mild excitation in the vestibular system on the affected side. OBJECTIVE: p-BPPV is considered to be caused by small particles dislodged from the utricular macula. While subjective visual horizontal (SVH) mainly reflects utricular function, there is less documentation on SVH in patients with p-BPPV. The purpose of this study was to clarify whether p-BPPV could affect SVH. PATIENTS AND METHODS: Twenty-eight patients with unilateral idiopathic p-BPPV were enrolled. For comparison, 17 patients with vestibular neuritis and 45 patients with cerebello-pontine angle (CPA) tumor were also examined. For measurement of SVH, we used a device that has a red bar of light-emitting diodes (LEDs) in front of the patient. Subjects were asked to rotate the bar to the position that they felt was horizontal in a completely dark room. RESULTS: Deviation of SVH toward the unaffected side down was seen in 82.1% (23/28) of patients with p-BPPV. Mean+/-SD deviation of SVH from the true horizontal to the unaffected side down was 0.49+/-1.21 degrees. Conversely, deviation of SVH was toward the affected side down in 88.2% of patients with vestibular neuritis and in 75.6% of patients with CPA tumor.     

Unilateral Vestibulotoxicity Due to Systemic Gentamicin Therapy

Systemic gentamicin can cause acute bilateral, simultaneous, symmetrical loss of vestibular function manifested by symptoms and signs of chronic vestibular insufficiency (ataxia and oscillopsia). We report 6 patients presenting with ataxia and oscillopsia, but without a history of vertigo, who had severe unilateral loss of vestibular function on caloric testing. The absence of vertigo in these patients could be explained by two possible mechanisms: either, the unilateral loss of vestibular function was subacute, occurring over several days so that compensation could occur, or bilateral vestibular loss occurred which was then followed by asymmetrical recovery of vestibular function. The second hypothesis is supported by the observation that vestibular hair cells can regenerate after aminoglycoside damage.     

Recovery of subjective visual horizontal after unilateral vestibular deafferentation by intratympanic instillation of gentamicin

The time course of the recovery of subjective visual horizontal (SVH) after unilateral vestibular deafferentation by intratympanic instillation of gentamicin was studied. Six patients who underwent intratympanic gentamicin instillation therapy for Meniere's disease (1 man and 5 women, 32 to 69 years of age) were enrolled in this study. For comparison, SVH in 23 healthy subjects (12 men and 11 woman, 23 to 48 years of age) was also measured. The mean +/- SD of SVH in healthy subjects was 0.0 +/- 1.1 deg. All of the 6 patients showed significantly deviated SVH toward the injected side-down at the early stage after the therapy. Although one patient showed recovery of SVH to the normal range 25 days after the injection, the other patients required more time for recovery. Three patients did not show recovery to the normal range after 1 year. On the other hand, spontaneous nystagmus observed using an infrared CCD camera in total dark disappeared after 35 days (median). Patients who had normal vestibular evoked myogenic potentials before the therapy showed a tendency of delay of recovery of SVH. The reasons why the recovery of SVH took longer than the disappearance of spontaneous nystagmus are discussed in this report.     

Outcomes of uvulopalatopharyngoplasty with harmonic scalpel after failure of continuous positive airway pressure in sleep apnea syndrome

The subjective visual horizontal (SVH) was measured by means of a small rotatable luminous line in darkness in the upright body position and at 10, 20 and 30° of body tilt to the right and left prior to, and during a follow-up period after, stapedotomy in 12 patients with otosclerosis. In the acute stage after surgery, SVH in the upright body position was significantly tilted away from the operated side. In addition, the perception of roll tilt towards the operated side (K_op) was significantly increased after stapedotomy, while the perception of roll tilt towards the healthy side (K_he) showed a slight but not significant reduction. After exclusion of two outliers, a statistically significant correlation was found between changes in K_op and in K_he. The slope of the regression line was 1.8 : 1, probably corresponding to a preference of the utricle for ipsilateral as opposed to contralateral head tilt. In four patients there was a weak (&;lt;1°/s) spontaneous nystagmus, not systematically related to the side of surgery, while in most cases there were no nystagmus or subjective vertigo symptoms. These specific changes in the subjective horizontal show that the otolithic effects on perception can be dissociated from canal effects. Further, the results are opposite to those for patients with unilateral loss of vestibular function. The tilt of SVH after stapedotomy indicates an increase in resting activity of utricular afferents. In addition, based on recent theories on otolith function, we suggest that an increased activity in saccular afferents is of major importance for the changes in roll-tilt perception because of its interaction with the utricle on the central nervous level.     

Vestibular-evoked myogenic potential in patients with unilateral vestibular neuritis: abnormal VEMP and its recovery

The incidence of inferior vestibular nerve disorders in patients suffering from unilateral vestibular neuritis and the recovery of these disorders were evaluated by monitoring the vestibular-evoked myogenic potential (VEMP). Eight patients ranged from 21 to 73 years that suffered from unilateral vestibular neuritis underwent VEMP and caloric testing. Abnormal VEMP was observed in two of the eight patients with unilateral vestibular neuritis. Two patients were diagnosed as having an inferior vestibular nerve disorder. One of these patients showed recovery of the inferior vestibular nerve function as assessed by the VEMP. Disorders of the inferior vestibular nerve function and their recovery was confirmed by our current results. The time course of recoveries of the superior and inferior vestibular nerve systems were similar in the two patients.     

VOR gain and phase in active head rotation tests of normal subjects and patients with peripheral labyrinthine lesions

The gain and phase of the vestibulo-ocular reflex (VOR) were studied by active head rotation tests in normal subjects and in patients with unilateral or bilateral lesions of vestibular function. The examination was performed under two conditions: alert-in-dark and with spatially-fixed target. The results were evaluated using a simplified model of vestibular response. Under alert-in-dark condition, the VOR grain and phase deficits were observed on rotation to the affected side in patients with unilateral lesions and bilaterally in patients with bilateral lesions. Under spatially-fixed-target condition, these patients showed a decrease in gain at higher frequencies but no phase lag was observed. The principally new advantage was that not only VOR gain but also VOR phase could be quantified using this active head rotation test. Therefore, for diagnosing VOR dysfunction, this active head rotation test is more useful than the active head rotation tests previously reported.     

Search-coil head-thrust and caloric tests in Ménière's disease

CONCLUSIONS: Our findings suggest that canal function is substantially preserved in subjects with active vertigo attacks as a result of Ménière's disease (MD). In these subjects, the head-thrust test (HTT) may not be as sensitive to canal dysfunction as traditional caloric testing. MD may differentially affect the low-frequency sensitivity of the canals. OBJECTIVE: Caloric tests have traditionally been used to characterize semicircular canal function in vestibular disorders, including MD. The quantitative HTT provides an objective measurement of semicircular canal function in the frequency and velocity ranges of normal head movements. The aim of this study was to compare the findings of caloric and HTTs in subjects with unilateral MD. MATERIAL AND METHODS: The study population consisted of 38 candidates for gentamicin treatment due to a high frequency of vertiginous attacks (25 males, 13 females; mean age 52.9 years; range 30-70 years). The duration of symptoms was 1-30 years (mean 5.3 years). Horizontal canal function was characterized with bithermal aqueous caloric tests and recordings of the angular vestibulo-ocular reflexes (aVORs) using the scleral search-coil technique during HTTs. The main outcomes were unilateral weakness (UW) on caloric testing and aVOR gain asymmetry (GA) during HTTs. A caloric response asymmetry of >20% was considered to be indicative of pathologic UW. A difference in GA during HTTs of >5.8% was considered significant. RESULTS: Twenty subjects (52.6%) showed abnormal results on one or both tests. Pathologic UW was present in 16 subjects (42.1%). During HTTs, 11 subjects (28.9%) showed pathologic GA. Seven subjects (18.4%) showed abnormal results on both tests. A significant correlation was found between UW and GA. However, pathologic GA during HTTs in subjects with unilateral MD was less frequent and the values smaller than those published for vestibular neuritis patients. Two subjects with unilateral MD had 100% UW, but none had >30% asymmetry on HTTs.     

Caloric and Search-Coil Head-Impulse Testing in Patients after Vestibular Neuritis

The objective of this study was to compare results of quantitative head-impulse testing using search coils with eye-movement responses to caloric irrigation in patients with unilateral vestibular hypofunction after vestibular neuritis. The study population consisted of an acute group (<3 days; N = 10; 5 male, 5 female; 26-89 years old) and a chronic group (>2 months; N = 14; 8 male, 6 female; 26-78 years old) of patients with unilateral vestibular hypofunction after vestibular neuritis. The testing battery included: (1) simultaneous measurement of eye and head rotations with search coils in a magnetic coil frame during passive Halmagyi-Curthoys head-impulse testing and (2) electronystagmography during bilateral monaural 44 degrees C-warm and 30 degrees C-cold caloric irrigation. The main outcome measures were (1) the gain of the horizontal vestibulo-ocular reflex during search-coil head-impulse testing and (2) the amount of canal paresis during caloric irrigation. All acute and chronic patients had a unilateral gain reduction during search-coil head-impulse testing. A pathological canal paresis factor was present in 100% of the acute patients but in only 64% of the chronic patients. The clinically suspected unilateral vestibular hypofunction resulting from vestibular neuritis was validated in all acute patients by both search-coil head-impulse and caloric testing. Hence, either of these tests is sufficient for diagnosis in the acute phase of vestibular neuritis. Chronic patients, however, were reliably identified only by search-coil head-impulse testing, which suggests that the low-frequency function of the labyrinths often becomes symmetrical, leading to a normal canal paresis factor.