上半规管BPPV

Until recently, the research community has had a relatively poor understanding of the anterior canal form of BPPV (AC-BPPV). To our knowledge, the only reported cases of AC-BPPV have occurred within the last 25 years. In 1994, Herdman et al. [16] analyzed 77 patients with BPPV and found that nine of them had AC-BPPV. In 1999, Honrubia et al. [17] performed a study in 292 patients with BPPV using an infrared camera and a Frenzel mirror,and found that four patients had AC-BPPV.

At present,the diagnosis of AC-BPPV mainly depends on the results of the D–H and the straight head-hanging (SHH) tests. These tests can induce a vertical down-beating nystagmus (DBN)with or without a torsional component. 
In the 2015 BPPV expert consensus document published by the Bárány Society, AC-BPPV is classifed as an emerging and controversial syndrome [32].

Therefore, the diagnosis and treatment of AC-BPPV require further study.

不同于后半规管BPPV眼震的旋转成分比较显著,上半规管BPPV患者Dix-Hallpike试验诱发的眼震垂直成分明显,旋转成分较弱,而且后者在裸眼情况下难以发现。虽然在上半规管BPPV健侧Dix-Hallpike试验时诱发的眼震更加显著,但临床判断患侧仍然比较困难。后半规管和上半规管BPPV时诱发的眼震成分的区别不同,主要是由两者空间位置的差别所致。前者和矢状位之间的夹角为56°,而后者则为41°。按照Ewald第一定律, 即眼震的平面和所受到刺激的半规管的平面平行, 由于角度偏小,上半规管壶腹嵴受到刺激时,旋转性眼震的矢量弱于后半规管,而垂直性眼震的矢量则更强,所以主要表现为下跳性眼震。