选择性外周前庭器化学切除及临床意义

用微量硫酸链霉素灌注豚鼠半规管。结果显示，经半规管向前庭外淋巴系统注入适当剂量的ＳＭ可以选择性破坏外周前庭感受器而不影响耳蜗功能。     

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.     

基于Matlab精确测量半规管在颅底中的方位

目的:确定半规管在颅底的精确方位,并分析其在不同年龄组、侧别和性别中的差异.方法:将45例正常人(90侧耳)的CT序列图像导入Mimics软件,读取确定半规管平面的标志点以及为确定以法兰克福平面为基准的标准空间坐标系的关键结构标志点的三维坐标,基于Matlab软件编制计算程序Laby Calculation,确定标准空间坐标系的相关方程,计算半规管在标准坐标系中的空间方位和面面夹角,最后对数据进行统计分析.结果:半规管的方位在不同年龄组和性别中具有一定的差异,而左右侧无明显差异,不同年龄组同侧半规管间面面夹角比较差异均无统计学意义(p＞0.05),提示随年龄增长同侧三个半规管方位的旋转可能是作为一个整体一同发生的.结论:本研究可为半规管发育研究提供形态数据,并对相关前庭功能检查和平衡功能障碍治疗提供依据和帮助.     

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.     

重复检查对诊断良性阵发性位置性眩晕的意义

目的 探讨重复检查对诊断良性阵发性位置性眩晕(BPPV)的重要性和相关临床特点.方法 回顾性分析复旦大学附属眼耳鼻喉医院耳鼻喉科2009年1月至2010年12月288例BPPV患者病例资料,观察需要多次检查获得确诊的病例的临床特点.结果 39例(13.5％)需要2次以上的体位诱发试验或者需要再次就诊才能诱发出典型的眼震,其中25例初诊时重复检查获得确诊,14例在复诊时获得确诊.需要多次检查者在年龄、性别构成及复位次数和总体无差别.需要多次检查者中水平半规管型BPPV比例为46.15％,明显高于总体的22.22％.另外在18例患者中观察到在第二次检查时出现潜伏期变短的现象.结论 对疑诊BPPV的患者,建议多次检查或安排复诊以观察到眼震.     

良性阵发性位置性眩晕患者326例临床特征分析

目的 探讨良性阵发性位置性眩晕的临床特征.方法 回顾性分析2009年8月至2011年7月诊治的326例良性阵发性位置性眩晕患者的临床特征,并对不同类型的良性阵发性位置性眩晕作比较.结果 良性阵发性位置性眩晕女性多见,50 ～60岁为发病高峰段,潜伏期为(1.52±1.22)s,无明显潜伏期患者43例(13.2％),眩晕发作持续时间中位数为10 s,持续时间＜60s患者312例(95.7％),持续时间60 ～180 s患者13例(4.0％);后半规管良性阵发性位置性眩晕与水平半规管良性阵发性位置性眩晕相比,潜伏期较长,分别为(1.74±1.21)s、(0.96±1.06)s(t=5.546,P＜0.01),而在性别构成、病程、眩晕持续时间上均无明显差异;后半规管壶腹嵴顶耳石症患者年龄较后半规管耳石症患者更年轻,持续时间更长;与水平半规管耳石症相比,水平半规管壶腹嵴顶耳石症患者潜伏期、持续时间均较长,年龄更大.结论 良性阵发性位置性眩晕以后半规管受累常见,与水平半规管相比,后半规管良性阵发性位置性眩晕潜伏期更长;水平半规管壶腹嵴顶耳石症与水平半规管耳石症相比年龄更大,潜伏期、持续时间更长.     

The response of primary horizontal semicircular canal neurons in the rat and guinea pig to angular acceleration

Summary In rats and guinea pigs, primary afferent neurons from the horizontal semicircular canal were divided into two categories, regular and irregular, on the basis of the regularity of their resting activity. Regular neurons tend to have higher average resting rates than irregular neurons and in response to a constant angular acceleration stimulus of 16.7 deg/s² regular neurons tended to have lower sensitivity and longer time constants than irregular cells. Some irregular neurons are more sensitive to incremental accelerations than to decremental accelerations of the same magnitude, whereas regular neurons tend to show symmetrical sensitivity.In response to sinusoidal angular acceleration stimuli (fixed frequencies) in the range 0.01–1.5 Hz, cells which fired regularly at rest tended to have smaller gain and longer phase lag re acceleration at most frequencies than irregular cells. Transfer functions were obtained for averaged data for regular and irregular neurons separately in both species.In both species there is evidence of systematic variation between neurons within each category, and this systematic variation is obscured by averaging across neurons.     

Vestibulo-collic reflex (VCR) in mice

The vestibulo-collic reflex (VCR) attempts to stabilize head position in space during motion of the body. Similar to the better-studied vestibulo-ocular reflex, the VCR is subserved by relatively direct, as well as indirect pathways linking vestibular nerve activity to cervical motor neurons. We measured the VCR using an electromagnetic technique often employed to measure eye movements; we attached a loop of wire (head coil) to an animal’s head using an adhesive; then the animal was gently restrained with its head free to move within an electromagnetic field, and was subjected to sinusoidal (0.5–3 Hz) or abrupt angular acceleration (peak velocity approximately 200°/s). Head rotation opposite in direction to body rotation was assumed to be driven by the VCR. To confirm that the compensatory head movements were in fact vestibular in origin, we plugged the horizontal canal unilaterally and then retested the animals 2, 8 and 15 days after the lesion. Two days after surgery, the putative VCR was almost absent in response to abrupt or sinusoidal rotations. Recovery commenced by day 8 and was nearly complete by day 15. We conclude that the compensatory head movements are vestibular in origin produced by the VCR. Similar to other species, there are robust compensatory mechanisms that restore the VCR following peripheral lesions.     

Initial vestibulo-ocular reflex during transient angular and linear acceleration in human cerebellar dysfunction

During transient, high-acceleration rotation, performance of the normal vestibulo-ocular reflex (VOR) depends on viewing distance. With near targets, gain (eye velocity/head velocity) enhancement is manifest almost immediately after ocular rotation begins. Later in the response, VOR gain depends on both head rotation and translation; gain for near targets is decreased for rotation about axes anterior to the otoliths and augmented for rotation about axes posterior to the otoliths. We sought to determine whether subjects with cerebellar dysfunction have impaired modification of the VOR with target distance. Eleven subjects of average age 48 +/- 16 years (mean +/- standard deviation, SD) with cerebellar dysfunction underwent transients of directionally unpredictable whole-body yaw rotation to a peak angular acceleration of 1000 or 2800 degrees/s2 while viewing a target either 15 cm or 500 cm distant. Immediately before onset of head rotation, the lights were extinguished and were relit only after the rotation was completed. The axis of head rotation was varied so that it was located 20 cm behind the eyes, 7 cm behind the eyes (centered between the otoliths), centered between the eyes, or 10 cm anterior to the eyes. Angular eye and head positions were measured with magnetic search coils. The VOR in subjects with cerebellar dysfunction was compared with the response from 12 normal subjects of mean age 25 +/- 4 years. In the period 35-45 ms after onset of 2800 degrees/s2 head rotation, gain was independent of rotational axis. In this period, subjects with cerebellar dysfunction had a mean VOR gain of 0.5 +/- 0.2, significantly lower than the normal range of 1.0 +/- 0.2. During a later period, 125-135 ms after head rotation about an otolith-centered axis, subjects with cerebellar dysfunction had a mean VOR gain of 0.67 +/- 0.46, significantly lower than the value of 1.06 +/- 0.14 in controls. Unlike normal subjects, those with cerebellar dysfunction did not show modification of VOR gain with target distance in the early response and only one subject showed a correct effect of target distance in the later response. The effect of target distance was quantitatively assessed by subtracting gain for a target 500 cm distant from gain for a target 15 cm distant. During the period 35-45 ms after the onset of 2800 degrees/s2 head motion, only two subjects with cerebellar loss demonstrated significant VOR gain enhancement with a near target, and both of these exhibited less than half of the mean enhancement for control subjects. During the later period 125-135 ms after the onset of head rotation, when VOR gain normally depended on both target location and otolith translation, only one subject with cerebellar dysfunction consistently demonstrated gain changes in the normal direction. These findings support a role for the cerebellum in gain modulation of both the canal and otolith VOR in response to changes in distance. The short latency of gain modification suggests that the cerebellum may normally participate in target distance-related modulation of direct VOR pathways in a manner similar to that found in plasticity induced by visual-vestibular mismatch.     

The influence of head position and head reorientation on the axis of eye rotation and the vestibular time constant during postrotatory nystagmus

Summary Reorienting the head with respect to gravity during the postrotatory period alters the time course of postrotatory nystagmus (PRN), hastening its decline and thereby reducing the calculated vestibular time constant. One explanation for this phenomenon is that the head reorientation results in a corresponding reorientation of the axis of eye rotation with respect to head coordinates. This possibility was investigated in 10 human subjects whose eye movements were monitored with a three-dimensional magnetic field — search — coil technique using a variety of head reorientation paradigms in a randomized order during PRN following the termination of a 90°/s rotation about earth vertical. Average eye velocities were calculated over two time intervals: from 1 s to 2 s and from 7 s to 8 s after cessation of head rotation. The time constant was estimated as one third of the duration of PRN. For most conditions, a reorientation of the head with respect to gravity 2 s after the rotation had stopped did not significantly alter the direction of the eye velocity vector of PRN with respect to head coordinates. This strongly indicates that, in humans, PRN is mainly stabilized in head coordinates and not in space coordinates, even if the otolith input changes. This finding invalidates the notion that the shortening of PRN due to reorientation of the head could be due to a change of the eye velocity vector towards a direction (torsion), which is not detectable with the eye recording methods (electrooculography) used in earlier studies. The results regarding the vestibular time constant basically confirm earlier findings, showing a strong dependence on static head position, with the time constant being lowest if mainly the vertical canals are stimulated (60° nose up and 90° left ear down). In addition, the time constant was drastically shortened for tilts away from upright. The reduction in vestibular time constant with head reorientation cannot be explained solely on the basis of the dependence of the time constant on static head position. A clear example is provided by head reorientations back towards the upright position, which results in a decrease in the time constant, rather than an increase that would be expected on the basis of static head position.