上半规管良性阵发性位置性眩晕诊断试验分析和物理引擎耳石运动观察

目的 对上半规管良性阵发性位置性眩晕（BPPV）诊断试验进行分析，了解其诊断机制。方法 建立标准空间坐标系的膜迷路模型，设定膜迷路不同位置结石，基于物理引擎三维物理仿真，分析Dix Hallpike试验和仰卧悬挂头位试验耳石运动情况，进而推断所诱发眼震表现。结果 Dix-Hallpike试验和仰卧悬挂头位试验所有位置的结石都有一定程度的运动，并能诱发椭圆囊的结石经总管进入半规管。出现下跳眼震的情况，包括结石从椭圆囊进入后半规管，对侧后半规管结石向壶腹运动，上半规管的结石从壶腹嵴帽底部滑动到顶部，后者重复诊断实验仍为下跳眼震。重复10次观察，试验结果一致。结论 对于上半规管BPPV的诊断标准，还需要重新评估，观察眼震动态变化是必要的，其诊断方法需要改良。     

良性阵发性位置性眩晕的诊断和治疗

目的：探讨良性阵发性位置性眩晕(BPPV)的诊治方法。方法：回顾性分析8例BPPV的临床资料。对所有患者全面采集病史及耳神经学检查，并施行Dixt-Hallpike试验及仰卧侧头位试验，按BPPV的不同类型分别采用Epley耳石复位法和Lempert翻滚法进行治疗。结果：8例BPPV中有5例属于后半规管性BPPV(PC—BPPV)，2例为水平半规管性BPPV(HC—BPPV)，1例为混合型。采用上述两种治疗方法后效果良好。8例患者经1～7次治疗后症状均缓解。结论：根据典型临床表现及体位试验可明确诊断，根据不同类型BPPV采用不同的复位治疗方法，Epley耳石复位法及Lempert翻滚法是治疗BPPV的首选治疗方法。     

半规管与动物敏捷度

正半规管是脊椎动物内耳的一个古老组成部分。在有颌动物(有颌骨的脊椎动物)的听泡中,骨性管道和其中的膜性管道组成了半规管,每侧听泡中各有上、外、后3个半规管,代表空间3个不同的平面,分别感受运动过程中头部在不同方向的旋转~([1])。大脑将半规管的传人冲动与耳石、视觉和本体感觉的信息进行整合分析,进而调整运动过程中躯体的姿势和动作~([2])。注视锁定是半规管最重要的功能之一,这一功能是通过前庭眼反射和前庭丘反射实现的,在运动中眼外肌和颈部肌肉需要配合躯体     

基于磁共振数据的三维半规管建模空间方向测量

目的测量半规管相互夹角和空间方向。方法对16例磁共振3D-CISS序列内耳检查影像,分割半规管结构建立三维模型,生成3D PDF文件,在各半规管取3点坐标,通过数学方法对同侧和双侧的半规管相互夹角以及各半规管和水平面的夹角进行计算。结果左右后半规管夹角为98.49°±12.07°,可以推测后半规管和矢状面的夹角为49.25°±6.04°。左右水平半规管夹角为171.58°±3.78°;左侧后半规管和右侧前半规管夹角为165.56°±5.78°,右侧后半规管和左侧前半规管夹角为164.74°±6.46°,左侧水平半规管和水平面夹角为19.43°±3.02°,右侧水平半规管和水平面夹角22.11°±4.12°。结论左右共同平面对半规管近乎平行,后半规管和矢状面的夹角大于45°,两侧半规管总脚分叉点和眼球下缘平面更加接近水平面。     

数值模拟前庭系统膜迷路的生物力学响应

目的研究平衡感受器嵴顶对旋转椅试验的生物力学响应,为前庭系统功能状态的评估提供定量分析的平台。方法基于健康志愿者右侧颞骨完整的组织切片数据进行三维几何重建。运用拉格朗日法数值模拟头前倾30毅、频率0.8Hz、幅度依40毅的正弦摆动旋转椅试验中受试者前庭系统膜迷路的生物力学响应。结果右耳水平半规管嵴顶峰值位移为54.2μm,后规管嵴顶峰值位移为15.9μm;右耳前半规管嵴顶峰值位移为43.7μm,但是左右耳响应相同,对眼球运动的作用相互抵消;向右旋转,右耳水平半规管壶腹嵴嵴顶法向位移从管侧偏向椭圆囊侧,左耳水平半规管壶腹嵴嵴顶法向位移从椭圆囊侧偏向管侧,向左旋转时则相反。结论数值模拟得到的嵴顶的生物力学响应符合Flourens定律和Ewald定律。     

成人颞骨骨迷路的解剖学研究及其临床意义

目的:对成人颞骨骨迷路进行解剖观察和测量,为临床提供解剖学基础。方法:制作26侧成人颞骨骨迷路标本进行观察和测量。结果:(1)半规管长度以后半规管最长,前半规管次之,外半规管最短。(2)半规管横断面呈椭圆形,其弓顶处管腔纵径大于横径。(3)壶腹端、单脚端、总脚端均近似圆形。后、前、外半规管壶腹端的纵径分别为:1.94mm,1.95mm,1.92mm。外半规管单脚端纵径为1.20mm,前、后半规管总脚端纵径为1.60mm。(4)三个半规管弓除外半规管弓在同一平面上外,前、后半规管弓均不在同一平面上,而呈不同程度的扭曲。(5)同侧三半规管之间并非相互垂直。(6)26侧中前半规管位于弓状隆突下的有16侧(61.54％),余10侧(38.46％)与弓状隆突不相重叠。结论:本研究结果为骨迷路结构研究增添了新的内容,为临床内耳手术的开展提供解削学基础和参考数据。     

耳石复位法治疗后半规管良性阵发性位置性眩晕分析

目的 对耳石复位法治疗后半规管良性阵发性位置性眩晕的疗效进行研究分析.方法 选取60例后半规管良性阵发性位置性眩晕患者,分为两组,实验组患者采用耳石复位法进行治疗,对照组患者采用常规药物治疗.结果 实验组患者治疗总有效率为86.7％,平均治疗时间为(7.3±2.5)d;对照组患者治疗总有效率为66.7％,治疗时间为(15.7±3.2)d.结论 采用耳石复位法治疗后半规管良性阵发性位置性眩晕,疗效确切,可将其作为临床治疗的首选方法.     

数值模拟人双耳感受体位变化的机制

目的探究双耳3对半规管在感受有角运动时力学行为表达的规律。方法采用有限元法数值模拟一例健康人头部水平正弦转动时左、右耳3对半规管的力学响应。结果各平衡感受器嵴顶局部位移响应随着嵴顶位置改变而变化,但是3对嵴顶的体积应变响应是规律的,每对嵴顶均以与激励相同的频率等幅度膨胀或收缩。水平、前、后半规管3个嵴顶的体积应变幅值绝对值的比值恒定,近似为1.00︰0.80︰1.72。此外,水平半规管和前半规管嵴顶体积应变响应的相位相同,且与头转动速度的相位约相差14.4°,与后半规管嵴顶体积应变响应的相位相差180°。结论嵴顶体积应变可以较好地表征3对半规管感受有角运动的规律,其幅值、频率和相位可以分别反映刺激角速度的幅值、频率和相位,这一规律为进一步建立前庭眼反射的数量依存关系奠定基础,同时为眼震检查定量评估前庭功能提供理论依据。     

正常人内耳MR成像观察及测量研究

目的 :为内耳疾病的定位诊断和显微手术提供正常人内耳的MRI图像及解剖学数据。方法 :选择 33例无任何耳部疾病的正常志愿者 ,采用MRI技术对两侧内耳同时进行三维重建成像 ,观察其形态结构 ,3个半规管和内听道进行测量。结果 :(1) 33例均能满意显示两侧内耳的解剖结构 ,前庭、耳蜗、半规管、内听道显示清晰。 (2 ) 3个半规管内周长、外周长、管腔面积均以后半规管最长 ,上半规管次之 ,外半规管最短。 (3) 3个半规管脚间距以上半规管最大 ,外半规管次之 ,后半规管最小。 (4 ) 3个半规管壶腹端直径均大于 2mm ,外半规管单脚端直径为 (1.37±0 .34)mm ,上、后半规管总脚端直径为 (1.73± 0 .15 )mm。 (5 )内听道四壁中以前壁最长 ,后壁最短。内耳门处上下径小于前后径 ;内听道面积为 35 .4 5mm2 。结论 :利用MRI技术能立体而直观地显示内耳的细微结构。     

人内耳半规管嵴顶时间常数的定量分析

目的 通过数值仿真和实验定量探究人内耳前庭半规管中的嵴顶时间常数,明确半规管编码角运动的时间过程。方法 建立人双耳半规管数值模型,通过流固耦合数值模拟嵴顶的生物力学响应,进而计算嵴顶的力学松弛时间常数。同时,对志愿者进行前庭眼反射实验,根据志愿者的眼震慢相角速度计算嵴顶的时间常数。结果 通过人内耳半规管数值模型计算得出的嵴顶力学松弛时间常数为3.75 s。通过实验测量得出平均嵴顶时间常数约为4.86 s。数值模型和实验中的结果近似保持一致。结论 人内耳前庭半规管中的嵴顶时间常数大约为4.86 s,反映了嵴顶力学松弛和半规管传入神经适应性的联合作用效果,体现了半规管编码角运动的时间过程。     

Clinical characteristics of benign paroxysmal positional vertigo in Korea: a multicenter study

Benign paroxysmal positional vertigo (BPPV) is characterized by episodic vertigo and nystagmus provoked by head motions. To study the characteristics of BPPV in a large group of patients in Korea, we retrospectively analyzed clinical features of 1,692 patients (women: 1,146, 67.7%; men: 54.6, 32.3%; mean age: 54.8+/-14.0 yr), who had been diagnosed as BPPV by trained neuro-otologists Dizziness Clinics. The diagnosis of BPPV was based on typical nystagmus elicited by positioning maneuvers. Posterior semicircular canal was involved in 60.9% of the patients, horizontal canal in 31.9%, anterior canal in 2.2%, and mixed canals in 5.0%. The horizontal canal type of BPPV (HC-BPPV) comprised 49.5% of geotropic and 50.5% of apogeotropic types. We could observe significant negative correlation between the proportion of HC-BPPV of each clinic and the mean time interval between the symptom onset and the first visit to the clinics (r=-0.841, p<0.05). Most patients were successfully treated with canalith repositioning maneuvers (86.9%). The high incidence of HC-BPPV in this study may be explained by relatively shorter time interval between the symptom onset and visit to the Dizziness Clinics in Korea, compared with previous studies in other countries.     

Spatial orientation of caloric nystagmus in semicircular canal-plugged monkeys

We studied caloric nystagmus before and after plugging all six semicircular canals to determine whether velocity storage contributed to the spatial orientation of caloric nystagmus. Monkeys were stimulated unilaterally with cold ( approximately 20 degrees C) water while upright, supine, prone, right-side down, and left-side down. The decline in the slow phase velocity vector was determined over the last 37% of the nystagmus, at a time when the response was largely due to activation of velocity storage. Before plugging, yaw components varied with the convective flow of endolymph in the lateral canals in all head orientations. Plugging blocked endolymph flow, eliminating convection currents. Despite this, caloric nystagmus was readily elicited, but the horizontal component was always toward the stimulated (ipsilateral) side, regardless of head position relative to gravity. When upright, the slow phase velocity vector was close to the yaw and spatial vertical axes. Roll components became stronger in supine and prone positions, and vertical components were enhanced in side down positions. In each case, this brought the velocity vectors toward alignment with the spatial vertical. Consistent with principles governing the orientation of velocity storage, when the yaw component of the velocity vector was positive, the cross-coupled pitch or roll components brought the vector upward in space. Conversely, when yaw eye velocity vector was downward in the head coordinate frame, i.e., negative, pitch and roll were downward in space. The data could not be modeled simply by a reduction in activity in the ipsilateral vestibular nerve, which would direct the velocity vector along the roll direction. Since there is no cross coupling from roll to yaw, velocity storage alone could not rotate the vector to fit the data. We postulated, therefore, that cooling had caused contraction of the endolymph in the plugged canals. This contraction would deflect the cupula toward the plug, simulating ampullofugal flow of endolymph. Inhibition and excitation induced by such cupula deflection fit the data well in the upright position but not in lateral or prone/supine conditions. Data fits in these positions required the addition of a spatially orientated, velocity storage component. We conclude, therefore, that three factors produce cold caloric nystagmus after canal plugging: inhibition of activity in ampullary nerves, contraction of endolymph in the stimulated canals, and orientation of eye velocity to gravity through velocity storage. Although the response to convection currents dominates the normal response to caloric stimulation, velocity storage probably also contributes to the orientation of eye velocity.     

Static roll and the vestibulo-ocular reflex (VOR)

Summary We measured the effect of static lateral tilt (roll) on the gain and time constant of the vestibulo-ocular reflex (VOR) in five normal subjects by recording both the horizontal and vertical components of eye velocity in space for rotation about an earth vertical axis with the head either upright or rolled to either side. The time constant of the VOR in the upright position was 19.6 ±3.2s (mean ± standard deviation). The time constant of the horizontal component with respect to the head decreased to 15.7±4.0s for 30° roll and to 12.7±2.7s for 60° roll. The time constant of the vertical component with respect to the head was 11.0±1.4 s for 30° roll and 7.5±1.6 s for 60° roll. The gain of the horizontal VOR with respect to space did not vary significantly with roll angle but a small space-vertical component to the VOR appeared during all rotations when the head was rolled away from upright. This non-compensatory nystagmus built up to a maximum of 2–3°/s at 17.0±4.7s after the onset of rotation and then decayed. These data suggest that static otolith input modulates the central storage of semicircular canal signals, and that head-horizontal and head-vertical components of the VOR can decay at different rates.     

Otolith-semicircular canal interaction during postrotatory nystagmus in humans

The otolith-semicircular canal interaction during postrotatory nystagmus was studied in ten normal human subjects by applying fast, short-lasting, passive head and body tilts (15, 30, 45, or 90° in the roll or pitch plane) 2 s after sudden stop from a constant-velocity rotation (100°/s) about the earth-vertical axis in yaw. Eye movements were measured with three-dimensional magnetic search coils. Following the head tilt, activity in the semicircular canal primary afferents continues to reflect the postrotatory angular velocity vector in head-centered coordinates, whereas otolith primary afferents signal a different orientation of the head relative to gravity. Despite the change in head orientation relative to gravity, postrotatory eye velocity decayed closely along the axis of semicircular canal stimulation (horizontal in head coordinates) for large head tilts (90°) and also for small head tilts (15–45°) for reorientations in the pitch plane. Only for small head tilts (15–45°) in the roll plane was there a reorientation of the eye rotation axis toward the gravitational vector. This reorientation was approximately compensatory for 15° head tilts. For 30° and 45° head tilts the eye rotation axis tilted toward the gravitational vector by about the same amount as for 15° head tilts. These results suggest that, with the exception of small head tilts in the roll plane, there was no compelling data showing a relationship between the eye rotation axis and head tilt and that postrotatory nystagmus is largely organized in head-centered rather than gravity-centered coordinates in humans. This indicates a rudimentary, nonlinear, and direction-specific interaction of semicircular canal and otolith signals in the central vestibular system in humans.     

Three-dimensional spatial characteristics of caloric nystagmus

We investigated the three-dimensional spatial characteristics of caloric nystagmus during excitation and inhibition of the lateral semicircular canal in five normal human subjects. Each subject was repositioned in 45 degrees steps at 1-min intervals such that the right lateral semicircular canal plane was reoriented in pitch, from 135 degrees backwards from the upright position to 135 degrees forwards, while the right ear was continuously stimulated with air at 44 degrees C. In orientations in which caloric stimulus resulted in excitation of the right lateral semicircular canal, the eye velocity axis was orthogonal to the average orientation of the right lateral semicircular canal plane. However, in orientations in which caloric stimulus resulted in inhibition of the right lateral semicircular canal, the eye velocity axis was orthogonal to the average orientation of the left and not the right lateral semicircular canal plane. These findings suggest that velocity and direction of caloric nystagmus depend not only on the absolute magnitude of vestibular activity on the stimulated side but also on the differences in activity between the left and right vestibular nuclei, most probably mediated centrally via brainstem commissural pathways.     

Role of irregular otolith afferents in the steady-state nystagmus during off-vertical axis rotation.

1. During constant velocity off-vertical axis rotations (OVAR) in the dark a compensatory ocular nystagmus is present throughout rotation despite the lack of a maintained signal from the semicircular canals. Lesion experiments and canal plugging have attributed the steady-state ocular nystagmus during OVAR to inputs from the otolith organs and have demonstrated that it depends on an intact velocity storage mechanism. 2. To test whether irregularly discharging otolith afferents play a crucial role in the generation of the steady-state eye nystagmus during OVAR, we have used anodal (inhibitory) currents bilaterally to selectively and reversibly block irregular vestibular afferent discharge. During delivery of DC anodal currents (100 microA) bilaterally to both ears, the slow phase eye velocity of the steady-state nystagmus during OVAR was reduced or completely abolished. The disruption of the steady-state nystagmus was transient and lasted only during the period of galvanic stimulation. 3. To distinguish a possible effect of ablation of the background discharge rates of irregular vestibular afferents on the velocity storage mechanism from specific contributions of the dynamic responses from irregular otolith afferents to the circuit responsible for the generation of the steady-state nystagmus, bilateral DC anodal galvanic stimulation was applied during optokinetic nystagmus (OKN) and optokinetic afternystagmus (OKAN). No change in OKN and OKAN was observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Epley and Semont maneuvers in the treatment of bening paroxymal postural vertigo

To compare the effectiveness of the 'repositioning' Epley maneuver and the 'liberatory' Semont maneuver in the treatment of benign paroxysmal positional vertigo (BPPV) of the posterior semicircular canal, a prospective study was performed, with 3 months of followup. A consecutive sample of 100 patients was included in two groups (age-and-sex matched) with a similar number of patients with idiopathic BPPV in each group. Group I was treated using the 'repositioning' maneuver and group II, the 'liberatory' maneuver. At weeks 1, 4, and 12 during the study, the proportion of patients without positional nistagmus was identified, and patients gave an evaluation of their subjective improvement (as a percentage). When positional nystagmus was evident, the corresponding maneuver was used again. Sixty percent of the patients were without nystagmus after the single use of any of the maneuvers. At the end of the study, more than 90% of patients were without nystagmus, with a 90% median value of subjective improvement. Patients with idiopathic BPPV showed a similar response to treatment as patients with BPPV associated to other disorders. We conclude that both maneuvers are effective for the treatment of BPPV of the posterior semicircular canal.     

Axon collaterals to the extraocular motoneuron pools of inhibitory vestibuloocular neurons activated from the anterior, posterior and horizontal semicircular canals in the cat

The branching pattern of inhibitory vestibuloocular neurons and their synaptic contacts with extraocular motoneurons were studied by means of spike-triggered averaging and local stimulation techniques. Individual vestibuloocular neurons activated by stimulation of the ampullary nerve of the anterior semicircular canal (ACN) inhibited motoneurons in both the ipsilateral (i-) trochlear nucleus and i-inferior rectus motoneuron pools. Individual vestibuloocular neurons receiving input from the ampullary nerve of the posterior semicircular canal (PCN) inhibited motoneurons in both the i-inferior oblique and i-superior rectus motoneuron pools. Probably, these axonal trajectories underlie conjugate eye movement during vertical head rotation. No conclusive evidence was found to indicate that single inhibitory vestibular neurons receiving input from the horizontal semicircular canal (HCN) give off axon collaterals to the i-abducens and the contralateral medial rectus motoneurons. A separate projection of HCN-related neurons to motoneurons supplying the lateral and medial rectus muscles might be useful for convergence during horizontal head movement.