出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/07/05 19:33:04」(JST)
| Benign paroxysmal positional vertigo | |
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Exterior of labyrinth of the inner ear.
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| Classification and external resources | |
| Specialty | Otorhinolaryngology |
| ICD-10 | H81.1 |
| ICD-9-CM | 386.11 |
| OMIM | 193007 |
| DiseasesDB | 1344 |
| MedlinePlus | 001420 |
| eMedicine | ent/761 emerg/57 neuro/411 |
| Patient UK | Benign paroxysmal positional vertigo |
| MeSH | D014717 |
Benign paroxysmal positional vertigo (BPPV) is a disorder arising in the inner ear. Its symptoms are repeated episodes of positional vertigo, that is, of a spinning sensation caused by changes in the position of the head.[1] BPPV is the most common cause of the symptoms of vertigo.[2]
Patients do not experience other neurological deficits such as numbness or weakness, and if these symptoms are present, a more serious etiology such as posterior circulation stroke or ischemia, must be considered.
The spinning sensation experienced from BPPV is usually triggered by movement of the head, will have a sudden onset, and can last anywhere from a few seconds to several minutes. The most common movements patients report triggering a spinning sensation are tilting their head upwards in order to look at something, and rolling over in bed.[2]
Within the labyrinth of the inner ear lie collections of calcium crystals known as otoconia or otoliths. In patients with BPPV, the otoconia are dislodged from their usual position within the utricle and migrate over time into one of the semicircular canals (the posterior canal is most commonly affected due to its anatomical position). When the head is reoriented relative to gravity, the gravity-dependent movement of the heavier otoconial debris (colloquially "ear rocks") within the affected semicircular canal causes abnormal (pathological) fluid endolymph displacement and a resultant sensation of vertigo. This more common condition is known as canalithiasis.
In rare cases, the crystals themselves can adhere to a semicircular canal cupula rendering it heavier than the surrounding endolymph. Upon reorientation of the head relative to gravity, the cupula is weighted down by the dense particles thereby inducing an immediate and maintained excitation of semicircular canal afferent nerves. This condition is termed cupulolithiasis.
There is evidence in the dental literature that malleting of an osteotome during closed sinus floor elevation, otherwise known as osteotome sinus elevation or lift, transmits enough percussive and vibratory forces capable of detaching otoliths from their normal location and leading to the symptoms of BPPV.[3][4]
It can be triggered by any action which stimulates the posterior semi-circular canal, including:
BPPV may be made worse by any number of modifiers which may vary between individuals:
An episode of BPPV may be triggered by dehydration, such as that caused by diarrhea. For this reason, it commonly occurs in post-operative patients who have diarrhea caused by post-operative antibiotics.
BPPV is one of the most common vestibular disorders in patients presenting with dizziness; migraine is implicated in idiopathic cases. Proposed mechanisms linking the two are genetic factors and vascular damage to the labyrinth.[5]
Although BPPV can occur at any age, it is most often seen in people over the age of 60.[6] Besides aging, there are no major risk factors known for developing BPPV, although previous episodes of trauma to the head or inner ear infections known as labyrinthitis, may predispose individuals to future development of BPPV.[2]
The inside of the ear is composed of an organ called vestibular labyrinth. The vestibular labyrinth includes semicircular canals which contain fluids, and fine hair like sensors that act as a monitor to the rotations of the head. An important structure in the inner ear includes the Otolith organs which contain crystals that are sensitive to gravity. These crystals are responsible for the sensitivity of head positions and can also be dislocated, causing them to get inside one of the semicircular canals, which causes dizziness.
The condition is diagnosed by the patient's history, and by performing the Dix-Hallpike maneuver and/or the roll test.[7][8]
The Dix-Hallpike test is a common test performed by examiners to determine whether the posterior semicircular canal is involved.[8] It involves a reorientation of the head to align the posterior semicircular canal (at its entrance to the ampulla) with the direction of gravity. This test will reproduce vertigo and nystagmus characteristic of posterior canal BPPV.[7]
When performing the Dix-Hallpike test, patients are lowered quickly to a supine position with the neck extended by the clinician performing the maneuver. For some patients, this maneuver may not be indicated and a modification may be needed that also targets the posterior semicircular canal. Such patients include those who are too anxious about eliciting the uncomfortable symptoms of vertigo and those who may not have the range of motion necessary to comfortably be in a supine position. Obesity can also present a challenge when performing this assessment. The modification involves the patient moving from a seated position to side-lying without their head extending off the examination table, such as with Dix-Hallpike. The head is rotated 45 degrees away from the side being tested and the eyes are examined for nystagmus. A positive test is indicated by patient report of a reproduction of vertigo and nystagmus. Both the Dix-Hallpike and the side-lying testing position have yielded similar results and as such the side-lying position can be used if the Dix-Hallpike cannot be performed easily.[9]
The roll test can determine whether the horizontal semicircular canal is involved.[7] The roll test requires the patient to be in a supine position with his/her head in 20° of cervical flexion. Then the examiner quickly rotates the head 90° to the left side, and checks for vertigo and nystagmus. This is followed by gently bringing the head back to the starting position. The examiner then quickly rotates the head 90° to the right side, and checks for vertigo and nystagmus.[7] In this roll test, the patient may experience vertigo and nystagmus on both sides, but rotating towards the affected side will trigger a more intense vertigo. Similarly, when the head is rotated towards the affected side, the nystagmus will beat towards the ground and be more intense.[8]
As mentioned above, both the Dix-Hallpike and roll test provoke the signs and symptoms in subjects suffering from archetypal BPPV. The signs and symptoms patients with BPPV experience are typically a short-lived vertigo, and observed nystagmus. In some patients, though rarely, the vertigo can persist for years. Assessment of BPPV is best done by a health professional skilled in management of dizziness disorders, commonly a physiotherapist, audiologist or other medical physician.
The nystagmus associated with BPPV has several important characteristics which differentiate it from other types of nystagmus.
Although rare, CNS disorders can sometimes present as BPPV. A practitioner should be aware that if a patient whose symptoms are consistent with BPPV, but does not show improvement or resolution after undergoing different particle repositioning maneuvers, which are detailed in the Treatment section below, need to have a detailed neurological assessment and imaging performed to help identify the pathological condition.[10]
Vertigo, a distinct process sometimes confused with the broader term, dizziness, accounts for about six million clinic visits in the United States every year; between 17 and 42% of these patients eventually are diagnosed with BPPV.[1] Other causes of vertigo include:
A number of maneuvers have been found to be effective including: the Epley maneuver, the Semont maneuver, and to a lesser degree Brandt-Daroff exercises.[12] Both the Epley and the Semont maneuver are equally effective.[12]
The Epley maneuver employs gravity to move the calcium build-up that causes the condition.[13] This maneuver can be performed during a clinic visit by health professionals or taught to people to practice at home.[14] Postural restrictions after the Epley maneuver increases its effect somewhat.[15]
When practiced at home, the Epley maneuver is more effective than the Semont maneuver. The most effective repositioning treatment for posterior canal BPPV is the therapist-performed Epley combined with home practiced Epley maneuvers.[16] Devices like the DizzyFIX can help users conduct the Epley maneuver at home and are available for the treatment of BPPV.[17]
The Epley maneuver does not address the actual presence of the particles (otoconia), rather it changes their location. The maneuver aims to move these particles from some locations in the inner ear which cause symptoms such as vertigo, and reposition them to where they do not cause these problems.
The Semont maneuver has a cure rate of 90.3%.[18] It is performed as follows:
In the Semont maneuver, patients themselves are able to achieve canalith repositioning.[14]
The Brandt-Daroff exercises may be prescribed by the clinician as a home treatment method usually in conjunction with particle repositioning maneuvers or in lieu of the particle repositioning maneuver. The exercise is a form of habituation exercise, designed to allow the patient to become accustomed to the position which causes the vertigo symptoms. The Brandt-Daroff exercises are performed in a similar fashion to the Semont maneuver; however, as the patient rolls onto the unaffected side, the head is rotated toward the affected side.[19] The exercise is typically performed 3 times a day with 5-10 repetitions each time, until symptoms of vertigo have resolved for at least 2 days.[7]
For the Lateral (Horizontal) canal, a separate maneuver has been used for productive results. It is unusual for the lateral canal to respond to the canalith repositioning procedure used for the posterior canal BPPV. Treatment is therefore geared towards moving the canalith from the lateral canal into the vestibule.[20] The roll maneuver or its variations are used and involves rolling the patient 360 degrees in a series of steps to reposition the particles.[10][21] This maneuver is generally performed by a trained clinician who begins seated at the head of the examination table with the patient supine[22] There are four stages, each a minute apart and at the third position the horizontal canal is oriented in a vertical position with the patient's neck flexed and on forearm and elbows.[22] When all four stages are completed, the head roll test is repeated and if negative treatment ceases.[22]
Medical treatment with anti-vertigo medications may be considered in acute, severe exacerbation of BPPV, but in most cases are not indicated. These primarily include drugs of the anti-histamine and anti-cholinergic class, such as meclizine and scopolamine respectively. The medical management of vestibular syndromes has become increasingly popular over the last decade, and numerous novel drug therapies (including existing drugs with new indications), have emerged for the treatment of vertigo/dizziness syndromes. These drugs vary considerably in their mechanisms of action, with many of them being receptor or ion channel-specific. Among them, include betahistine or dexamethasone/gentamicin for the treatment of Ménière's disease, carbamazepine/oxcarbazepine for the treatment of paroxysmal dysarthria and ataxia in multiple sclerosis, metoprolol/topiramate or valproic acid/tricyclic antidepressant for the treatment of vestibular migraine, and 4-aminopyridine for the treatment of episodic ataxia type 2 and downbeat and upbeat nystagmus.[23] These drug therapies offer symptomatic treatment, and do not affect the disease process or resolution rate. Medications may be used to suppress symptoms during the positioning maneuvers if the patient's symptoms are severe and intolerable. More dose-specific studies are required however, in order to determine the most effective drug(s) for both acute symptom relief and long term remission of the condition.[23]
Surgical treatments, such as a semi-circular canal occlusion, do exist for BPPV but carry the same risk as any neurosurgical procedure. Surgery is reserved as a last resort option for severe and persistent cases which fail vestibular rehabilitation (including particle repositioning and habituation therapy).
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| リンク元 | 「BPV」 |
| 拡張検索 | 「benign paroxysmal vertigo in childhood」 |
| 関連記事 | 「paroxysm」「paroxysmal vertigo」「benign」「paroxysmal」 |