A 55-year-old woman presented to the emergency department complaining of dizziness. Several hours earlier she abruptly felt “the room spinning and moving back and forth.” Simultaneously, she experienced nausea, vomiting, and gait unsteadiness. The dizziness exacerbated with head movement. She denied head or neck pain, photophobia, phonophobia, auditory symptoms, weakness, numbness, diplopia, dysarthria, dysphonia, dysphagia, history of recent illness, prior dizziness, or headache. Medical history included hyperlipidemia and hypertension.
一位55岁的患者因突发眩晕来到急诊。几个小时前，她突然感到“房子旋转和前后摇晃”。同时她感到恶心、呕吐和步态不稳。随着头的活动眩晕加重。她否认头痛、颈部疼痛、畏光、畏声、听觉症状，无肢体麻木无力、复视、构音障碍、发音困难、吞咽困难等症状，无近期患病史，先前无头晕或头痛史。既往有高脂血症和高血压病史。
Question for consideration：
1. What is the differential diagnosis for acute vertigo?
思考问题：
1. 急性眩晕的鉴别诊断有那些？
To determine the cause of acute vertigo, it is important to know whether it is transient (seconds to minutes) or prolonged (hours to days); a single episode of vertigo or a recurrence; if it is positionally provoked (e.g., benign paroxysmal positional vertigo); and if there are any accompanying symptoms or signs.
判断急性眩晕的病因，了解以下这些是重要的：眩晕是短暂的（几秒到几分钟）还是长时的（几个小时到几天）；单次发作性眩晕还是反复发作性眩晕；是否是位置诱发的眩晕（比如，良性阵发性位置性眩晕）；是否有伴随症状或者体征。
The most common causes of acute prolonged vertigo include a peripheral vestibulopathy, Me´nie `re syndrome, migrainous vertigo, or brainstem or cerebellar ischemia. 1 This discussion is limited to the distinction between a peripheral vestibulopathy and ischemia. The acute vestibular syndrome (AVS) develops over seconds to hours and is characterized by vertigo, nausea, vomiting, gait instability, head motion intolerance, and nystagmus. 2–4
急性持续性眩晕的最常见的病因包括前庭外周性疾病，梅尼埃病，偏头痛型眩晕，脑干或小脑缺血。这个讨论限于前庭外周性疾病和脑缺血之间的鉴别。急性前庭综合征持续时间从几秒到几小时，特点为眩晕、恶心、呕吐、步态不稳、不敢活动头部和眼震。
It is caused by either an acute peripheral vestibulopathy (APV) or brainstem/cerebellar ischemia, and similarities in presentation often make the distinction a diagnostic challenge.
急性周围性前庭疾病（APV）或者脑干/小脑缺血都可引起这些症状，症状相同常常使得鉴别诊断困难。
Transient ischemic attacks can cause acute vertigo with rapid resolution but vertigo resulting from a stroke, like an APV, may last days to weeks. Vertigo caused by ischemia is almost always accompanied by other neurologic symptoms and signs but may occur in isolation. 2–5
短暂性脑缺血发作可能导致快速缓解的急性眩晕，但眩晕源自卒中，类似急性周围性前庭疾病，可以持续几天到几周。由缺血导致的眩晕大多数常常伴随有其他的神经系统症状和体征，但是也可能孤立发生。
An APV is characterized by acute prolonged vertigo, oscillopsia (the visual illusion of movement of a stationary object due to spontaneous nystagmus), unilateral canal paresis with a positive head impulse test (HIT), nausea, vomiting, exacerbation of vertigo with head movement, and imbalance. 2–4
APV的特点是急性长时性眩晕、振动幻视（由于自发性眼震而出现对固定物体的运动视错觉）、单侧半规管轻瘫伴头脉冲试验（HIT）阳性、恶心、呕吐、头部活动会加重眩晕、以及不平衡感。
Depending on the presence or absence of auditory symptoms, an APV is further classified as either labyrinthitis or vestibular neuritis, respectively. Vertigo is maximal within minutes to hours and can persist for days to weeks. There may be a viral prodrome or a history of brief vertiginous attacks in the days prior to the onset of prolonged vertigo. 1
根据有无听觉症状，将APV进一步细分为迷路炎和前庭神经炎。眩晕在几分钟到几小时内最严重，并且持续几天到几周的时间。这可能是病毒感染的前驱症状或者持续眩晕发作前数天的短暂眩晕发作。
Questions for consideration:
1. What is the pathophysiology of nystagmus?
2. How is the vestibular system assessed on physical examination?
思考问题
1. 眼震的病理生理机制是什么？
2. 体格检查时，如何评估前庭功能？
In an acute destructive lesion affecting 1 labyrinth, such as an APV, symptoms result from ipsilesional afferent hypoactivity and relative contralesional hyperactivity from the vestibulocochlear nerve. During a normal head turn to the left, there is left-greater-than-right asymmetry in afferent vestibular signals and the eyes drift to the right to maintain stable vision (i.e., vestibule-ocular reflex or VOR).6
在影响到迷路的急性破坏性病变中，如APV，症状来源于同侧前庭耳蜗神经传入冲动减少，对侧相对活跃。正常头转向左侧时，传入前庭的信号不对称、左侧较右侧明显，眼球漂移到右侧保持视觉固定（即前庭-眼反射或VOR）。
A right APV is perceived as a leftward head turn even though the head is still. As a result, the eyes continuously drift to the right (slow phase of nystagmus), and a position reset mechanism (fast phase) quickly brings the eyes back to the left (to midline) (figure 1).6
右侧的APV被理解为是向左侧的头位旋转，尽管头部保持不动。因此，眼球持续漂移到右边（眼球震颤的慢相），位置重置的机制（快相）迅速使眼球回到左侧（中间）（图1）
图1 急性周围性前庭病的周围性眼震的病理生理
急性周围性前庭疾病的眼震是混合的水平-旋转眼震，提示整个前庭神经或一个迷路内所有半规管的病变。单个半规管的刺激使眼球在不同方向移动（即水平、垂直或旋转）。在右侧的急性周围性前庭疾病中，眼震的方向取决于未受损的左侧迷路。左侧前半规管和后半规管的相反方向抵消了垂直运动，仅留下轻微的旋转眼震，然而左侧的水平半规管无抵消力量导致水平眼震。这产生了（用红色标记）朝向病侧耳朵的慢相（病理性），和（用黑色表示）远离病侧耳朵的快相（复位）。眼球震颤方向以快相的方向命名。眼震出现在第一眼位，向两边凝视时眼球向同一方向（单向）跳动。LAC=左侧前半规管，LHC=左侧水平半规管；LPC=左侧后半规管；RAC=右侧前半规管；RHC=右侧水平半规管；RPC=右侧后半规管。
The nystagmus is of larger amplitude when gazing in the direction of the fast phase (i.e.,Alexander law). The horizontal component of peripheral vestibular nystagmus is inhibited with fixation (there is a poor torsional fixation mechanism), 7 which does not occur with central causes of vestibular nystagmus.
当凝视快相的方向时，眼球震颤的振幅比较大（亚历山大定律），周围源性前庭性眼球震颤的水平震颤成分可被固视抑制（旋转眼震机制不清），中枢源性前庭性眼球震颤不能被固视抑制。
Since the intensity of peripheral nystagmus is influenced by fixation, observation under various conditions can help distinguish central vs peripheral causes of vertigo as peripheral nystagmus inhibits with fixation, and conversely, increases with fixation removed.
因为周围源性眼震的强度受固视的影响，所以在不同情况下的观察有助于区别中枢源性还是周围源性眩晕，周围源性眼震被固视抑制，相反抑制解除后眼震增强。
Occlusive funduscopy is performed by visualizing the optic disc with an ophthalmoscope and then covering the patient’s viewing eye, thus removing fixation, which enhances peripheral nystagmus but has no effect on central nystagmus.7 Similarly, the penlight cover test involves having the patient fixate on a penlight, and then covering 1 eye, thus removing fixation as the uncovered eye continues to view only the bright penlight.8
进行闭合性眼底检查，通过检眼镜观察视神经盘，然后遮住患者另一侧的眼睛，解除固视，此方法增强周围源性眼震，但是不会影响中枢源性眼震。同样的，笔灯覆盖试验是让患者注视笔灯，然后遮住一眼，这样解除固视，未遮盖的眼继续只看笔灯的光。
Having the patient view a featureless scene such as a piece of white paper has a similar effect: since there is no feature available for foveation, fixation is suppressed.7 Dynamic assessment of the vestibular system includes the HIT, which tests angular VOR function (figure 2).9
让病人看无特征的景象，比如一张白纸有相同的结果：因为没有可获得的特征，固视被抑制。前庭系统的动态评估包括HIT,它是测试角度前庭-眼反射（VOR）功能（图2）。
图2 头脉冲试验评估角度前庭-眼反射
(A）正常时，快速向右侧转头 20 °，患者能保持注视检查者的鼻子（即目标）（B）右侧周围性前庭病的患者，当头被快速转向右侧时，因为前庭眼反射功能减弱，视线随头移动，迫使一种向左侧的代偿性捕捉眼扫视使视线重新注视检查者的鼻子。
Although a peripheral pattern of nystagmus with an abnormal HIT implies labyrinthine or vestibular nerve dysfunction, it is important to recognize that the etiology may be ischemia. The vascular supply to the inner ear is via the internal auditory artery, so a “peripheral” lesion can be from infarction.10
尽管外周性的眼球震颤伴HIT异常提示迷路或前庭神经功能障碍，但重要的是要考虑到缺血也可能是其病因。内耳供血来自内听动脉，因此看似“外周”的病变可能是梗死所致。
Another important sign to look for in the AVS is a skew deviation, which is a nonparalytic prenuclear vertical ocular misalignment due to an imbalance of utricular inputs to the ocular motor system. It is often accompanied by features of the ocular tilt reaction (OTR), which includes the triad of skew deviation, head tilt, and ocular counterroll.11 A skew deviation is best demonstrated during alternate cover testing demonstrating vertical correction of the uncovered eye to maintain fixation, or subjectively with Maddox rod testing. A skew deviation and a fourth nerve palsy may present similarly (figure 3). A skew deviation occurs most commonly with brainstem or cerebellar lesions, but also may be seen with a lesion anywhere from the utricle to the interstitial nucleus of Cajal in the rostral midbrain.11
确定急性前庭综合征的另外一个重要体征是眼偏斜，这是无神经肌肉麻痹的核前性眼垂直错位，源于椭圆囊输入到眼球运动系统的信号不平衡。它常常伴随着眼倾斜反应（OTR）的特征，包括三部分：眼偏斜、头倾斜、眼旋转。眼偏斜最好的证明是在交替覆盖试验时，证明未覆盖眼为维持固视进行垂直向矫正，或者进行主观Maddox rod检查。眼偏斜和第四对颅神经（滑车神经）麻痹可能出现相同的症状（图3）。眼偏斜最常见于脑干和小脑病变，但是也可见于从椭圆囊到中脑嘴部卡哈尔（Cajal）间质核联系通路上任何一处的病变。
图3 Maddox rod试验鉴别第四颅神经麻痹和眼偏斜
（A）左侧第四对颅神经麻痹 与（B）眼偏斜比较。 按照惯例， 马多克斯杆（Maddox rod）放置在右眼上方。在（A）和（B）中原发性凝视中有垂直的错位，左眼比右眼高（即左上斜视）。在（A）图中，向对侧凝视（患侧眼内收），向下凝视，向同侧头倾斜（没有显示）证明光和水平线之间的垂直间隔更大，诊断左侧第四颅神经麻痹（即左眼上斜视程度更大），。在（B）图中，眼偏斜导致左眼上斜视是一种共性，意味着垂直错位在各个凝视方向是一致的。在第四对颅神经麻痹中看到的头倾斜，是一种代偿（即头向对侧倾斜最大程度地减少由于患眼的内旋受损导致的眼的错位），与之相比，在OTR中的头倾斜发生在眼球旋转的相同方向。
Other signs of central localization of acute vertigo include direction-changing (i.e., gaze-evoked or bidi-rectional) nystagmus, pure horizontal, torsional, or vertical nystagmus, impaired or asymmetric smooth pursuit, inability to suppress the VOR (combined eye-head tracking of moving targets), dysmetric saccades, and associated brainstem and long tract signs.1,7
另外，急性眩晕中枢性定位的其它体征包括不断变换方向的眼震（即凝视诱发或双向眼震），单纯的水平、旋转或垂直性眼震，受损或不对称的平稳跟踪，不能被抑制的前庭眼反射（联合眼头跟踪移动的目标），扫视辨距不良，脑干体征和长束征。
In our patient, blood pressure was 143/79 mmHg and general medical examination including otoscopy were normal. In primary gaze there was left-beating horizontal-torsional jerk nystagmus that intensified with left gaze, and lessened but remained left-beating in right gaze (video, first half, on the Neurology® Web site at www.neurology.org). The nystagmus intensified with removal of fixation during occlusive funduscopy and the penlight cover test. The HIT was normal to the left but abnormal to the right (video, second half), demonstrating a catch-up saccade, confirming a hypoactive right VOR. Suppression of the VOR, smooth pursuit, and saccadic eye movements were normal.
我们的患者，血压是143/79mmHg，一般的医学检查包括耳镜都是正常的。在起初的凝视中，向左侧的水平旋转急动性眼震，向左注视时眼震增强，向右注视时眼震仍存在，但会减弱（视频前半部）。在闭合性眼底检查和笔灯覆盖试验中，解除固视会使眼震增强。HIT向左侧是正常的，但是向右侧是不正常的（视频后半部），可见一次捕捉眼扫视，证实右侧前庭眼反射功能减退。抑制前庭眼反射、 平稳跟踪、眼扫视运动均正常。
There was no vertical misalignment. When testing tandem gait, there were multiple side-steps to the right, and she could not maintain balance with Romberg testing. The remainder of the neurologic examination was normal.
检查没有发现垂直的错位。当检查踵趾步态时，多次向右侧倾倒，Romberg试验不能保持平衡。其余神经系统检查正常。
视频
Questions for consideration:
1. What are the most common manifestations of cerebellar ischemia?
2. What are the 3 most important bedside ocular motor tests to differentiate a stroke from an APV?
3. How has the examination narrowed the differential diagnosis in this patient?
思考问题：
1. 小脑缺血最常见的表现是什么？
2. 鉴别卒中与急性周围前庭疾病三个最重要的床旁眼动试验是什么？
3. 检查如何缩小该患者的鉴别诊断范围？
In a series of 66 patients with isolated cerebellar infarctions, vertigo and lateropulsion (defined as an irresistible sensation of falling to one side) were the most common symptoms.5
66例有孤立性小脑梗死病人。眩晕和走路向一侧倾倒（定义为一种不可抵抗的向一边的倾倒感）是最常见的症状。
Although vertigo and lateropulsion can each occur in isolation with a cerebellar stroke, other signs and symptoms are typically present, including limb ataxia, nausea/vomiting, truncal ataxia, dysarthria, nystagmus, headache, confusion, or somnolence.3,5
尽管眩晕和走路向一侧倾倒会单独存在于小脑梗死患者中，其它的体征和症状也是有代表性的，包括上肢的共济失调、恶心/呕吐、躯干的共济失调、构音障碍、眼球震颤、头痛、意识模糊或嗜睡。
A stroke in the posterior inferior cerebellar artery territory can cause a “pseudovestibular neuritis” manifesting as isolated vertigo without auditory or other symptoms, but typically has a normal HIT.3 A superior cerebellar artery stroke can cause a “pseudointoxication” picture because of gait or truncal ataxia with dysarthria, or “pseudogastroenteritis” with nausea and vomiting.
小脑后下动脉供血区卒中能导致一种假性前庭神经炎，表现为孤立的眩晕，无听觉或其他症状，但通常HIT正常。 因为步态或者躯干的共济失调，且伴有构音障碍或者伴有恶心及呕吐等“假性胃肠炎”症状，小脑上动脉供血区卒中可出现“假性中毒”的表现。
The internal auditory artery (IAA) is an end artery from the anterior inferior cerebellar artery (AICA) that supplies the vestibulocochlear nerve, cochlea, and vestibular labyrinth. Due to a paucity of collaterals, the IAA is vulnerable to ischemia. A labyrinthine infarction usually presents with sudden loss of hearing and vertigo accompanied by other AICA-territory signs (e.g., cerebellar, lateral pontine, or midbasilar syndromes).2,3
内听动脉（IAA）是小脑前下动脉(AICA)的终末动脉，供应前庭蜗神经、耳蜗和前庭迷路。由于缺少侧支循环，IAA容易发生缺血。迷路的梗死常常表现为突然耳聋，眩晕伴随其他的AICA供血区的症状（例如小脑、脑桥外侧，或者基底动脉中间综合征。
However, isolated labyrinthine ischemia may herald AICA infarction.2,10In a series of 82 patients with AICA strokes, 80 had acute prolonged vertigo and vestibular dysfunction of peripheral, central, or combined origin;35 had acute prolonged vertigo with audiovestibular loss; 24 had acute prolonged vertigo without audiovestibular loss, while a selective loss of vestibuar (4) or cochlear (3) function was much less common.10
然而，孤立的迷路卒中可能预示着AICA供血区梗死。82例AICA供血区卒中患者中，80例有急性持续的眩晕和周围源的、中枢源的或者混合的前庭功能障碍；35例急性持续眩晕伴有听力、前庭功能受损，24例急性持续眩晕无听力、前庭功能受损，而选择性前庭功能或耳蜗功能受损更少见。
AICA strokes have also been referred to as “pseudolabyrinthitis.”3 In patients presenting with the acute vestibular syndrome, the combination of direction-changing nystagmus, skew deviation, and a normal HIT were more sensitive in detecting stroke than MRI (table).4
AICA卒中也一直被考虑为“假性迷路炎”，急性前庭综合征的患者中，结合不断变换方向的眼震、眼偏斜和正常的HIT比MRI预测卒中更敏感（表）。
表格 周围性和中枢性急性前庭综合征的鉴别
临床症状 | 周围性 | 中枢性 | 注释 |
眼震 | 单向的，水平-旋转混合性眼震，符合亚历山大定律 恒定频率的慢相眼震，患侧耳朵向下躺时眼震增强 | 可以改变方向 单纯的水平，旋转或垂直眼震，慢相眼震频率持续增强或者减弱 | 周围性眼震随着眼球固视而抑制，眼球固视解除眼震增强，而中枢性眼震很少被眼球固视抑制 |
头-脉冲试验（HIT）） | 异常 | 通常正常 | 前庭神经核、第8对颅神经入脑干区域、小脑下部病变可引起异常的HIT |
眼偏斜 | 无 | 可能存在 | 轻度的偏斜可能是椭圆囊病变的表现，不过很少见到；但是明显的偏斜合并复视提示中枢病变 |
合并症状或体征 | 听力减退或耳鸣，轻度步态不稳，朝病变侧的方向偏斜 | 头痛或颈痛（如果是突发长时的、严重的头痛或颈痛，特别要考虑中枢性），无力，麻木，复视，构音不清，发声困难，吞咽困难，霍纳征，跌倒发作（突然跌倒但意识清楚），步态不稳，走路向一侧倾斜 | 表现为孤立性眩晕的中枢性病变不常见。 |
A normal HIT strongly indicates a central process, but an abnormal HIT is a less reliable indicator of a peripheral lesion because of APV mimics (i.e.,ischemia of the vestibular nucleus, root entry zone of the eighth cranial nerve, or caudal cerebellum may cause an abnormal HIT).12–14 In addition to the findings on bedside examination, vertigo due to cerebrovascular disease should be considered if any of the following factors are present: stroke risk factors, risk of vertebral artery dissection, abrupt onset, inability to ambulate, paucity of nausea and vomiting with marked gait instability or severe nausea and vomiting with little gait instability, or other accompanying central neurologic symptoms and signs.3
正常的HIT强烈提示中枢的病变，但是异常的HIT提示周围性病变不那么可靠，因为有很多和APV相似疾病（比如前庭神经核、第8对颅神经入脑干区域或小脑下部缺血可能导致异常的HIT）。除了床旁的检查结果之外，如果出现以下任一情况，应该考虑脑血管病引起的眩晕：卒中危险因素，椎动脉夹层风险，突然发病，无法行走，恶心呕吐症状轻而行走不稳明显或者恶心呕吐症状重而没有步态不稳，或者其它伴随的中枢神经系统症状和体征。
Our patient had a right APV without auditory symptoms, and was diagnosed with vestibular neuritis. Prior to evaluation by the authors and within 24 hours of symptom onset, a brain MRI was found to be normal. Although brainstem/cerebellar infarctions may be missed acutely on MRI, the positive HIT, unidirectional nystagmus, and absent skew deviation all pointed away from a central process, and therefore an MRI was arguably unnecessary.4 Her symptoms improved significantly over several days with only antiemetics, and vestibular rehabilitation was recommended.
我们的患者有右侧APV，没有听觉的症状，被诊断为前庭神经炎。发病24小时内，在作者检查之前，头颅MRI检查正常。尽管MRI上脑干和小脑急性期梗死可能被漏掉，但是HIT阳性，单向的眼球震颤，无眼偏斜，所有这些都不支持中枢性病变，因此MRI检查可以说是不必要的。仅仅是给了止吐药，几天后她的症状明显改善，推荐给予前庭康复治疗。
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