[The analysis of nystagmus in patients with posterior canal benign paroxysmal positional vertigoin positioning test].

OBJECTIVE: To analyze and summarize nystagmus of patients with posterior canal benign paroxysmal positional vertigo (BPPV) in positioning test,and to improve the diagnosis and treatment of posterior canal BPPV (PSC-BPPV).

METHOD: The present study was conducted on 175 patients who had unilateral BPPV of the posterior semicircular canal (PSC). Their positional nystagmus recorded by videnonystagmography in Dix-Hallpike test,roll test and roll over test were analyzed to summarize the characteristics of nystagmus on nystagmograph of PSC-BP-PV.

RESULT: Of the 175 patients, lesion was located in the left PSC in 69 (39.4%) patients,the right PSC in 106 (60. 6%)patients. The nystagmus of patients with PSC-canalithiasis showed upward on the vertical phase of nystagmograph and orientated the different side on horizontal phase in the head hangging position. The horizontal phase pointed to the contralateral side in 47(26. 9%) patients, the ipsilateral contralateral side in 100(57. 1%) patients,no significant reverse ingredients in 28(16.0%) patients. When these patients returned to sit,139(79.4%) patients showed down beating positioning nystagmus, whereas 36 (20. 6%) patients with no nystagmus only had a short vertigo or dizziness. The horizontal phase of the 139 patients pointed to the contralateral side in 40(22. 9%) patients,the ipsilateral contralateral side in 68(38. 9%) patients,no significant reverse ingredients in 31(17. 7%) patients. In roll test,12 patients of the right PSC-BPPV presented an up-beating rotatory nystagmus when the head turned to right,and 5 patients of the left PSC-BPPV presented a down-beating rotatory nystagmus when the head turned to left. When the patients changed body from the left lateral position to the right lateral position in the roll over test, 74(42. 3%) patientsshowed vertical positioning nystagmus. In 30 patients who presented an up-beating nystagmus, there were 25(83. 3%) patientscame from the right PSC-BPPV. In 44 patients who presented a down-beating nystagmus, there were 36(81. 8%) patientscame from the left PSC-BPPV. The direction of the vertical nystagmus was highly correlated with the judgment about the side of the PSC-BPPV in roll over test (P<0. 01).

CONCLUSION: The patient with PSC-canalithiasis showed an uncertain direction in torsional nystagmus in Dix-Hallpike test,the diagnosis was mainly concern with the vertical nystagmus. When we found a rotatory nystagmus with much more up-beating nystagmus in roll test, it might be PSC-BPPV. We also can use the roll over test to diagnose the location of the otolith in which side of the PSC-BPPV.