Natural course of positional down-beating nystagmus of peripheral origin

The aim of this study was to assess the natural course of positional down-beating nystagmus (pDBN) and vertigo in patients with no evidence of central nervous system involvement and of presumed peripheral origin. Fifty-three patients with pDBN had a complete otoneurological examination. All subjects, apart from three (excluded from the study), showed no additional neurological signs and normal brain imaging. Patients were randomly assigned to two groups: with or without treatment with exercise. Patients were seen again after 24 h, and then weekly for up to 6 months. Forty-seven patients (94%) showed pDBN in the straight head-hanging position and in a Dix-Hallpike position. A torsional component was detected in 17 patients (34%). The mean latency and duration of pDBN was 4.7 ± 5 s and 40.1 ± 22 s, respectively. After 2 weeks, only 12 patients (24%) still had pDBN and all but one patient had recovered by 1 month. Twenty patients (40%) were diagnosed with a typical posterior canal benign paroxysmal positional vertigo (PC BPPV) before or after pDBN. This study assessed for the first time the natural course of presumed peripheral pDBN, which was characterized by a spontaneous remission in 24 patients in the first week and in 49 patients within 4 weeks. pDBN is much more common than previously suggested, with about the same frequency as lateral canal BPPV. Furthermore, the clinical characteristics of pDBN have been highlighted, as well as its possible relationship to PC BPPV.