Helminski Janet O
Department of Physical Therapy, Rosalind Franklin University, North Chicago, IL, United States.
Front Neurol. 2022 Oct 10;13:982191. doi: 10.3389/fneur.2022.982191. eCollection 2022.
Atypical posterior canal (PC) positional nystagmus may be due to the changes in cupular response dynamics from cupulolithiasis (cu), canalithiasis of the short arm (ca-sa), or a partial/complete obstruction-jam. Factors that change the dynamics are the position of the head in the pitch plane, individual variability in the location of the PC attachment to the utricle and the position of the cupula within the ampulla, and the location of debris within the short arm and on the cupula. The clinical presentation of PC-BPPV-cu is DBN with torsion towards the contralateral side in the DH positions and SHHP or no nystagmus in the ipsilateral DH position and no nystagmus upon return to sitting from each position. The clinical presentation of PC-BPPV-ca-sa is no nystagmus in the DH position and upbeat nystagmus (UBN) with torsion lateralized to the involved side upon return to sitting from each position.
A 68-year-old woman, diagnosed with BPPV, presented with DBN associated with vertigo in both DH positions and without nystagmus or symptoms on sitting up. In the straight head hanging position (SHHP), the findings of a transient burst of UBN with left torsion associated with vertigo suggested ipsicanal conversion from the left PC-BPPV-cu to canalithiasis. Treatment included a modified canalith repositioning procedure (CRP), which resulted in complete resolution. BPPV recurred 17 days later. Clinical presentation of BPPV included no nystagmus/symptoms in both the contralateral DH position and SHHP, DBN in the ipsilateral DH position without symptoms, and UBN with left torsion associated with severe truncal retropulsion and nausea on sitting up from provoking position. The findings suggested the left PC-BPPV-cu-sa and PC-BPPV-ca-sa. Treatment included neck extension, a modified CRP, and demi-Semont before complete resolution.
An understanding of the biomechanics of the vestibular system is necessary to differentially diagnose atypical PC-BPPV. DH test (DHT) findings suggest that PC-BPPV-cu presents with DBN or no nystagmus in one or two DH positions and sometimes SHHP and without nystagmus or no reversal/reversal of nystagmus on sitting up. The findings suggest PC-BPPV-ca-sa has no nystagmus in DH positions or DBN in the ipsilateral DH position and UBN with torsion lateralized to the involved side on sitting up.
非典型后半规管（PC）位置性眼球震颤可能是由于嵴顶结石症（cu）、短臂管结石症（ca-sa）或部分/完全阻塞-卡塞导致的嵴顶反应动力学变化引起的。改变动力学的因素包括头部在俯仰平面的位置、PC附着于椭圆囊的位置以及壶腹内嵴顶的位置的个体差异，以及短臂内和嵴顶上碎片的位置。PC-BPPV-cu的临床表现为在患侧向下（DH）位时向对侧扭转的背地性眼震（DBN），同侧DH位时为背地性水平眼震（SHHP）或无眼球震颤，且从每个位置恢复坐姿时均无眼球震颤。PC-BPPV-ca-sa的临床表现为DH位无眼球震颤，从每个位置恢复坐姿时向患侧扭转的上跳性眼震（UBN）。
一名68岁女性，诊断为良性阵发性位置性眩晕（BPPV），在两个DH位均出现与眩晕相关的DBN，坐起时无眼球震颤或症状。在直头悬挂位（SHHP），短暂出现与眩晕相关的伴有左旋的UBN，提示从左侧PC-BPPV-cu转变为管结石症。治疗包括改良的半规管复位法（CRP），结果完全缓解。17天后BPPV复发。BPPV的临床表现包括对侧DH位和SHHP均无眼球震颤/症状，同侧DH位有DBN但无症状，以及从诱发位坐起时伴有左旋的UBN，伴有严重的躯干后冲和恶心。这些表现提示左侧PC-BPPV-cu-sa和PC-BPPV-ca-sa。治疗包括颈部伸展、改良的CRP和半Semont法，最终完全缓解。
了解前庭系统的生物力学对于鉴别诊断非典型PC-BPPV是必要的。患侧向下试验（DHT）结果表明，PC-BPPV-cu在一个或两个DH位表现为DBN或无眼球震颤，有时在SHHP位也如此，坐起时无眼球震颤或眼球震颤无反转/反转。这些结果表明，PC-BPPV-ca-sa在DH位无眼球震颤或同侧DH位有DBN，坐起时向患侧扭转的UBN。
