Therapeutic efficacy of canalith reposition maneuver according to the determination method of lesion side in patients with persistent geotropic direction-changing positional nystagmus

Background: The Canalith Repositioning Maneuver (CRM) is often ineffective for persistent geotropic direction-changing positional nystagmus (DCPN). In these cases, determining the lesion side can be challenging, as the null plane side and the side with stronger nystagmus on the roll test are frequently opposite. Objectives: This study investigates whether the low therapeutic efficacy of CRM in persistent DCPN could be attributed to incorrect determination of the lesion side. Material and methods: This prospective randomized trial involved two groups of patients with persistent geotropic DCPN, categorized based on the method used to determine the lesion side: the null plane side and the side with stronger nystagmus on the head roll test. We assessed the therapeutic efficacy of CRM on the null plane side (null plane group) and the side with stronger nystagmus on the head roll test (stronger nystagmus group). Results: Both groups showed minimal or no immediate therapeutic effect of CRM, with a low short-term effect observed in both as well. No significant differences were found in the immediate and short-term therapeutic effects of CRM between the two groups. Conclusions and significance: The limited therapeutic effect of CRM in persistent geotropic DCPN does not appear to result from incorrect determination of the lesion side.