良性位置性眩晕

Review Article Primary Care 1590 · November 18, 1999 The New England Journal of Medicine B ENIGN P AROXYSMAL P OSITIONAL V ERTIGO J OSEPH M. F URMAN , M.D., P H .D., AND S TEPHEN P. C ASS , M.D., M.P.H. From the Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh (J.M.F.); and the Department of Otolaryn- gology, University of Colorado Health Science Center, Denver (S.P.C.). Ad- dress reprint requests to Dr. Furman at the Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, or at furman@pitt.edu. ©1999, Massachusetts Medical Society. ANY patients consult their doctors because of dizziness or poor balance. Dizziness is nonspecific; it may result from a disorder of almost any organ system. Thus, the differential di- agnosis for such patients is broad and should in- clude medical, neurologic, and otologic causes. Ver- tigo, which is the illusory sensation of motion of either oneself or one’s surroundings, may be a component of a patient’s dizziness. Benign paroxysmal positional vertigo is one of the most common types of vertigo. 1,2 This condition pre- sents as dizziness or vertigo of sudden onset that is provoked by certain changes in head position. The most common provocative movements are rolling over in bed, bending over, and looking upward. Although benign paroxysmal positional vertigo has long been recognized, 3,4 only more recently has its underlying pathophysiology been clarified and substantiated. 5-7 Free-floating particulate matter within the posterior semicircular canal of the vestibular labyrinth has been observed in vivo in several patients with this disor- der. 7,8 This finding led to the development of an in- novative bedside treatment in which the free-floating particles are moved from the posterior semicircular canal to another location within the vestibular laby- rinth. 9 Such maneuvers usually provide the patient with immediate, and often long-lasting, relief from vertigo. 9-11 Despite the seemingly simple and straightforward pathophysiology and treatment of benign paroxysmal positional vertigo, the diagnosis and treatment of this condition can be challenging. Patients may present with some but not all of the characteristic features of M typical benign paroxysmal positional vertigo, and there are several variants. There are several types of maneu- ver to treat the condition. TERMINOLOGY “Benign paroxysmal positional vertigo” is the term most commonly used to describe a disease with a characteristic clinical presentation believed to be caused by free-floating particles within the posterior semicircular canal. Vertigo is an important feature of this condition. The word “benign” is used to distin- guish between the types of vertigo caused by pe- ripheral vestibular ailments and the types of vertigo caused by intracranial neoplasms. In fact, however, benign paroxysmal positional vertigo can be a severe, disabling problem or a nagging nuisance responsible for constant frustration. The term “paroxysmal” re- flects an important and essential characteristic of the disorder: the vertigo is episodic rather than persistent. The use of the word “positional” implies a particular association between a patient’s symptoms and his or her head position with respect to gravity. However, the symptoms associated with benign paroxysmal po- sitional vertigo are elicited by a particular rotational movement of the head rather than by the final posi- tion of the head. A characteristic feature of benign paroxysmal po- sitional vertigo is an accompanying nystagmus. In the most common form of the condition, the position- ally provoked nystagmus contains both torsional and vertical components. The nystagmus associated with benign paroxysmal positional vertigo has led some authors to use the term “benign paroxysmal position- al nystagmus.” 12 PATHOGENESIS Our understanding of the pathogenesis of benign paroxysmal positional vertigo has improved dramat- ically because of intraoperative observations of ag- glomerated, free-floating particulate matter in the en- dolymph of the posterior semicircular canal 7,8 (Fig. 1A). These observations substantiated what were pre- viously only hypotheses that the movement of intra- labyrinthine debris underlies most cases of the con- dition. 5,6 Earlier writings, notably by Schuknecht, 13 postulated that debris adhering to the cupula, rather than free-floating debris in the semicircular canal, was responsible. 14 However, the action of free-float- ing debris is the currently accepted pathophysiologic mechanism for typical benign paroxysmal positional vertigo. On the basis of electron-microscopical exam- ination of particles obtained during surgery (Fig. 1B), the free-floating debris has been postulated to arise Downloaded from www.nejm.org on October 21, 2007 . Copyright © 1999 Massachusetts Medical Society. All rights reserved. PRIMARY CARE Volume 341 Number 21 · 1591 from within the vestibular labyrinth. The particles are most likely calcium carbonate crystals (otoliths) that are normally attached to a membrane within the utriculus, one of two gravity-sensitive structures in the inner ear. 8 The exact mechanism by which free-floating debris leads to paroxysmal vertigo and nystagmus is un- known, but presumably the movement of the debris causes alterations in endolymphatic pressure and thus cupular deflection. Also, several studies have reported postmortem data that indicate that a small percent- age of patients without an antemortem diagnosis of benign paroxysmal positional vertigo have debris in the semicircular canals. 15-17 Despite this uncertainty, all the clinical manifesta- tions of benign paroxysmal positional vertigo can be explained by a transitory movement of agglomerat- ed debris within the posterior semicircular canal. 5,6,18 Moreover, this pathophysiologic process is consis- tent with the epidemiologic features of the condi- tion, since head trauma is a frequent antecedent of benign paroxysmal positional vertigo, 4 presumably because of the dislocation of otoliths from the utricu- lus, which then migrate to the posterior semicircular canal, the most dependent structure in the vestibular labyrinth. CLINICAL MANIFESTATIONS AND EVALUATION Many patients report dizziness; they may also have vertigo. In some disorders, including benign paroxys- mal positional vertigo, vertigo is the most prominent symptom. In other disorders, however, the vertigo is less prominent, and dizziness, lightheadedness, and dysequilibrium may better characterize the patients’ symptoms. Patients with dizziness may also have im- paired balance. In some neurologic disorders, poor balance may be present without dizziness. Table 1 lists the most common causes of vertigo. Benign paroxys- mal positional vertigo, Meniere’s disease, migraine, vertebrobasilar insufficiency, and panic disorder are associated with recurrent vertigo. They can be distin- guished from one another by various characteristic symptoms. Benign paroxysmal positional vertigo is provoked by a change in position and lasts for sec- onds. In Meniere’s disease, the vertigo occurs sponta- neously, lasts for minutes to hours, and is accompanied by unilateral hearing loss and tinnitus. Migraine- associated vertigo is highly variable in duration and usually precedes or is accompanied by headache. The vertigo in vertebrobasilar insufficiency is associated Figure 1. Free-Floating Particles in Patients with Benign Paroxys- mal Positional Vertigo. Panel A shows debris (arrow) in the posterior semicircular canal as observed intraoperatively (photograph courtesy of Dr. Lorne Parnes). Panel B shows a scanning electron micrograph of an intralabyrinthine particle, obtained during surgery. The debris is thought to consist of calcium carbonate crystals that origi- nate in the utriculus of the vestibular labyrinth. Reprinted from Welling et al., 8 with the permission of the publisher. B A T ABLE 1. C OMMON C AUSES OF V ERTIGO . Otologic disorders Benign paroxysmal positional vertigo Meniere’s disease (endolymphatic hydrops) Vestibular neuronitis (labyrinthitis) Neurologic disorders Migraine-associated dizziness Vertebrobasilar insufficiency Panic disorder Downloaded from www.nejm.org on October 21, 2007 . Copyright © 1999 Massachusetts Medical Society. All rights reserved. 1592 · November 18, 1999 The New England Journal of Medicine with brain-stem symptoms such as diplopia, dysar- thria, and facial numbness. Vertigo is sometimes a symptom of a panic attack. Vestibular neuronitis usu- ally causes a single episode of vertigo that may last as long as one or two days. The most prominent symptom of benign paroxys- mal positional vertigo is vertigo that occurs in bed when a patient rolls into a lateral position. 3 Vertigo also commonly occurs when the patient is gazing upward (e.g., to place an object on a shelf ) or bend- ing forward (e.g., to tie his or her shoes). The initial onset of vertigo is often associated with nausea, with or without vomiting. Because few patients have pre- viously had sudden, unexpected vertigo of such in- tensity, the symptoms may be frightening and may lead to an immediate visit to the emergency room. Typically, each episode of vertigo lasts only 10 to 20 seconds. The natural history has not been well char- acterized, but it appears that benign paroxysmal po- sitional vertigo is usually a self-limited disorder that may be present for several weeks or even years, with remissions and recurrences occurring unpredictably. Most patients quickly learn to avoid the provocative head movements. This avoidance of movements that provoke vertigo is understandable but, ironically, tends to prolong the course of the condition. Some patients with benign paroxysmal positional vertigo have a more widespread balance disorder. 4,19 A unilateral reduction in the function of the hori- zontal semicircular canal is found in many patients. In addition, the condition often follows head trauma or vestibular neuronitis. In these patients, labyrin- thine dysfunction usually affects more than just the posterior semicircular canal, which is the portion of the inner ear affected in benign paroxysmal position- al vertigo. Thus, positionally provoked vertigo may be part of a constellation of symptoms that includes gait instability and dysequilibrium during rapid head movements. A diagnosis of benign paroxysmal positional verti- go can be established definitively through the Dix– Hallpike test 3 (sometimes erroneously called the Bá- rány or Nylen–Bárány test), as illustrated in Figure 2. The diagnostic criteria (Table 2) include the occur- rence during the Dix–Hallpike test of a characteristic mixed torsional and vertical nystagmus with the up- per pole of the eye beating toward the dependent ear and the vertical nystagmus beating toward the forehead. The nystagmus typically begins after a 1-to- 2-second latency, lasts for 10 to 20 seconds, and is associated with a sensation of rotational vertigo. Af- ter the patient returns to the seated position, nys- tagmus is again observed, but the direction of nystag- mus is reversed. Although no longer recommended as a diagnostic maneuver, because it may interfere with the immediate bedside treatment of benign paroxys- mal positional vertigo, repetition of the Dix–Hall- pike test results in a reduction in the intensity of ver- tigo and nystagmus. Observation of the patient’s eye movements during the Dix–Hallpike test can be im- proved through the use of specialized equipment to reduce visual fixation. However, because visual sup- pression of torsional nystagmus is minimal, 20 the nys- tagmus typically associated with the disorder can, in most cases, be observed directly. A question that often arises when assessing a patient with benign paroxysmal positional vertigo is whether there is a need for further specialized evaluation. In general, patients with this condition, especially patients who respond favorably to bedside treatment, do not require further specialized evaluation. However, pa- tients with abnormal findings on neurologic examina- tion, those with atypical positional nystagmus, those who do not respond to bedside treatment, and those whose dizziness or dysequilibrium cannot be attrib- uted entirely to benign paroxysmal positional verti- go should undergo further specialized evaluation. 21,22 EPIDEMIOLOGY Benign paroxysmal positional vertigo has been said to be the most commonly recognized vestibular dis- order 1 ; in one cohort of patients, the mean age at onset was 54 years, with a range of 11 to 84 years. 4 Froehling et al. estimated that the incidence is as high as 107 cases per 100,000 population per year. 23 How- ever, these authors did not require that patients meet strict diagnostic criteria. A study in Japan in which patients were considered to have benign paroxysmal positional vertigo only if they had nystagmus during a Dix–Hallpike test found an incidence of 10.7 cases per 100,000 per year. 24 In two other studies, the percentages of patients who presented to a specialty dizziness clinic who were found to have benign par- oxysmal positional vertigo were in nearly complete agreement, with 17 percent in one study 25 and 18 per- cent in the other. 11 Common antecedents of the dis- order include vestibular neuronitis and head trauma. In our experience, there is an association with vestib- ular neuronitis in 10 percent of patients and with head trauma in 20 percent of patients. Similarly, Baloh et al. reported that 15 percent of cases of benign par- oxysmal positional vertigo followed neurolabyrinthi- tis and 18 percent followed head trauma. 4 However, in most patients with benign paroxysmal positional vertigo, no antecedent association is found. 4 OTHER DISORDERS Although the vast majority of patients who present with paroxysmal positionally provoked vertigo asso- ciated with transitory nystagmus have benign parox- ysmal positional vertigo, a small fraction of patients have other disorders. The most common, horizontal- canal benign positional vertigo, is a disorder thought to be caused by free-floating debris in the horizontal rather than posterior semicircular canal. 26-29 Infrequently, patients with paroxysmal positional- Downloaded from www.nejm.org on October 21, 2007 . Copyright © 1999 Massachusetts Medical Society. All rights reserved. PRIMARY CARE Volume 341 Number 21 · 1593 Figure 2. The Dix–Hallpike Test of a Patient with Benign Paroxysmal Positional Vertigo Affecting the Right Ear. In Panel A, the examiner stands at the patient’s right side and rotates the patient’s head 45 degrees to the right to align the right posterior semicircular canal with the sagittal plane of the body. In Panel B, the examiner moves the patient, whose eyes are open, from the seated to the supine right-ear-down position and then extends the patient’s neck slightly so that the chin is pointed slightly upward. The latency, duration, and direction of nystagmus, if present, and the latency and duration of vertigo, if present, should be noted. The red arrows in the inset depict the direction of nystagmus in patients with typical benign paroxysmal positional ver- tigo. The presumed location in the labyrinth of the free-floating debris thought to cause the disorder is also shown. 45°S agitta l body plane Utriculus Posterior-canal ampulla Particles Posterior canal Superior canal A B Posterior canal Superior canal Utriculus Gravity Gravity Vantage point Vantage point Gravity Gravity Posterior-canal ampulla Particles Downloaded from www.nejm.org on October 21, 2007 . Copyright © 1999 Massachusetts Medical Society. All rights reserved. 1594 · November 18, 1999 The New England Journal of Medicine ly provoked symptoms have an underlying disorder of the central nervous system rather than an ailment of the peripheral vestibular system. 12,21,22,30 In rare in- stances, patients with tumors of the posterior fossa present with vertigo and nystagmus that are indistin- guishable from those found in benign paroxysmal positional vertigo. 22 TREATMENT The treatment currently recommended for benign paroxysmal positional vertigo is based on a bedside maneuver introduced by Epley. 9 The purpose of the maneuver, shown in Figure 3, is to relocate free- floating debris from the posterior semicircular canal into the vestibule of the vestibular labyrinth, where it presumably adheres, thus no longer causing verti- go on movement of the head. The maneuver takes advantage of the fact that the free-floating debris has a density that exceeds that of the surrounding endo- lymph. As a result, the debris can be moved within the labyrinth noninvasively through a sequence of head orientations with respect to gravity. Severe neck disease, a high-grade carotid stenosis, and unstable heart disease are contraindications to the maneuver shown in Figure 3. Two reports have described a heels-over-head rotational chair designed to control T ABLE 2. D IAGNOSTIC C RITERIA FOR B ENIGN P AROXYSMAL P OSITIONAL V ERTIGO . Vertigo associated with a characteristic mixed torsional and vertical nystag- mus provoked by the Dix–Hallpike test A latency (typically of 1 to 2 seconds) between the completion of the Dix– Hallpike test and the onset of vertigo and nystagmus Paroxysmal nature of the provoked vertigo and nystagmus (i.e., an increase and then a decline over a period of 10 to 20 seconds) Fatigability (i.e., a reduction in vertigo and nystagmus if the Dix–Hallpike test is repeated) Figure 3. Bedside Maneuver for the Treatment of a Patient with Benign Paroxysmal Positional Vertigo Affecting the Right Ear. The presumed position of the debris within the labyrinth dur- ing the maneuver is shown in each panel. The maneuver is a three-step procedure. First, a Dix–Hallpike test is performed with the patient’s head rotated 45 degrees toward the right ear and the neck slightly extended with the chin pointed slightly upward. This position results in the patient’s head hanging to the right (Panel A). Once the vertigo and nystagmus provoked by the Dix–Hallpike test cease, the patient’s head is rotated about the rostral–caudal body axis until the left ear is down (Panel B). Then the head and body are further rotated until the head is face down (Panel C). The vertex of the head is kept tilted downward throughout the rotation. The maneuver usually pro- vokes brief vertigo. The patient should be kept in the final, face- down position for about 10 to 15 seconds. With the head kept turned toward the left shoulder, the patient is brought into the seated position (Panel D). Once the patient is upright, the head is tilted so that the chin is pointed slightly downward. Utriculus Posterior- canal ampulla Particles A B C D Superior canal Utriculus Posterior-canal ampulla Posterior canal Superior canal Vantage point Posterior canal Superior canal Posterior canal Superior canal Gravity Gravity Gravity Vantage point Vantage point Vantage point Particles Gravity Particles Particles Downloaded from www.nejm.org on October 21, 2007 . Copyright © 1999 Massachusetts Medical Society. All rights reserved. PRIMARY CARE Volume 341 Number 21 · 1595 for v