Immediate and Short-Term Therapeutic Results between Direction-Changing Positional Nystagmus with Short-and Long-Duration Groups

Objectives: Clinicians sometimes treat patients with relatively long-duration geotropic direction-changing positional nystagmus (DCPN), without latency. Recently, the concept of a "light cupula" in the lateral canal that reveals persistent geotropic DCPN has been introduced. In the present study, we investigated the immediate and short-term therapeutic findings in long-duration DCPN. Design: The authors prospectively compared the therapeutic efficacy of a canalith-repositioning procedure (CRP) in short-and long-duration geotropic DCPN. Results: In patients with long-duration DCPN, the authors found no immediate therapeutic effect, and the number of patients showing short-term effects (on the next day) was very low compared with the comparable figure among those with short-duration DCPN. In addition, no cases exhibited canal conversion after the CRP. Conclusion: Our results suggest that CRP is not useful in patients with long-duration geotropic DCPN, and the pathogenesis of long-duration geotropic DCPN may not originate from free-floating debris but from deflection of the cupula.