Office-based differential diagnosis of transient and persistent geotropic positional nystagmus in patients with horizontal canal type of benign paroxysmal positional vertigo.

CONCLUSION:A 30 s observation of geotropic positional nystagmus is sufficient to distinguish persistent geotropic positional nystagmus (PGPN) from transient geotropic positional nystagmus (TGPN) in patients with horizontal canal type of benign paroxysmal positional vertigo (H-BPPV) in ENT office. OBJECTIVE:As a canalith repositioning procedure effectively treats H-BPPV with TGPN, but not PGPN, the differentiation between patients with PGPN and with TGPN is essential. The purpose of this study is to determine the observation period enough to distinguish TGPN from PGPN. METHODS:This study first analyzed positional nystagmus images recorded with an infrared CCD camera three-dimensionally in 47 patients with H-BPPV. PGPN is distinguished from TGPN in patients with H-BPPV precisely by means of time constant calculated form analysis of positional nystagmus. Ten-second and 30-s movies were made of positional nystagmus of the all 47 patients. Ten independent otolaryngologists were then asked to distinguish TGPN from PGPN after a 10 s or 30 s observation of the geotropic positional nystagmus images in 47 patients with H-BPPV. RESULTS:The sensitivity and specificity to distinguish TGPN from PGPN was 100% and 97% after 30 s observation, but 100% and 40% after 10 s observation, respectively.