良性位置性阵发性眩晕(BPPV)视图来源

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您请求的操作仅限于组中的用户:==临床相关解剖== [[Image: inner迷路2.jpg|frame|right|100px| Labyrinth内景|link=//m.houseofhawgs.com/File:Innerlabyrinth2.jpg]] "良性阵发性位置性眩晕" (" 'BPPV'')是一种特殊类型的眩晕，由头部相对于重力的位置变化引起。这种疾病是由内耳的问题引起的。其症状是反复发作的体位性眩晕，即由头部位置变化引起的旋转感。Neil Bhattacharyya、Reginald F. Baugh、Laura Orvidas、David Barrs、Leo J. Bronston、Stephen Cass、Ara A. Chalian、Alan L. Desmond、Jerry M. Earll、Terry D. Fife、Drew C. Fuller、MPH、James O. Judge、Nancy R. Mann、Richard M. Rosenfeld、Linda T. Schuring、Robert W. P. Steiner、Susan L. Whitney和Jenissa Haidari。[http://www.entnet.org/Practice/upload/BPPV-Els.pdf临床实践指南:良性阵发性位置性眩晕]。耳鼻喉头颈外科，2008,39,S47-S81前庭系统通过检测角加速度和线加速度来监测头部的运动和位置。内耳的3个半规管检测角加速度，它们彼此成直角。每条管道充满内淋巴，在底部有一个肿胀，称为壶腹。壶腹包含壶体，这是一种与内淋巴密度相同的胶状团块，它又附着在极化的毛细胞上。内淋巴对丘的运动可引起刺激或抑制反应，这取决于运动方向和特定的半规管< name="Lorne et al">Lorne S. Parnes, Sumit K. Agrawal和Jason Atlas。 [http://www.cmaj.ca/cgi/content/full/169/7/681 Diagnosis and management of benign paroxysmal positional vertigo (BPPV)]. CMAJ. September 30, 2003; 169 (7). There is a vestibular apparatus within each ear so under normal circumstances, the signals being sent from each vestibular system to the brain should match, confirming that the head is indeed rotating to the right, for example. Within the labyrinth of the inner ear lie collections of calcium crystals known as otoconia. In patients with BPPV, the otoconia are dislodged from their usual position within the utricle and they 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 or crystals) within the affected semicircular canal causes abnormal (pathological) fluid endolymph displacement in the affected ear. This fluid displacement will send a signal to the brain indicating that rotational movement is occuring. However, the vestibular apparatus in the unaffected ear will not be transmitting the same signal because there are no loose otoconia triggering the hair cells abnormally. This resultant mismatch in signals coming from the right and left vestibular systems lead to the sensation of vertigo. This more common condition is known as canalithiasis. Vertigo associated with this condition will be of short duration, even if the person with the condition stays in the provocative position, because the endolymph and otoconia will quickly come to a rest so the hair cells will no longer be displaced and triggering the signal to the brain. 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. Vertigo associated with this condition will not resolve until the head is moved out of the provocative position because even when the endolymph comes to a rest, the adhered otoconia will continue to displace the hair cells and trigger the signal of movement to the brain. It can be triggered by any action which stimulates the posterior semi-circular canal which may be: *Tilting the head *Rolling over in bed *Looking up or under *Sudden head motion BPPV may be made worse by any number of modifiers which may vary between individuals: *Changes in barometric pressure - patients often feel symptoms approximately two days before rain or snow *Lack of sleep (required amount of sleep may vary widely) *Stress

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