[THE SIGNIFICANCE OF TORSIONAL NYSTAGMUS ON THE ROLL REST]

To characterize a subgroup of patients that were diagnosed with benign paroxysmal positional vertigo of the posterior semicircular canal pBPPV, with findings of geotropic-torsional nystagmus on the roll rest (RT) that intensified on the Dix-Hallpike exam (DH).

The study population consisted of patients with the diagnosis of pBPPV. First, the roll test (RT) and then the DH test were performed. Characteristics were compared between group 1 - patients with a negative RT and positive DH (in keeping with pBPPV), and group 2- patients with a torsional-geotropic nystagmus on the RT, that intensified on DH. Patients from both groups were treated with the Epley maneuver. If the nystagmus continued, further Epley maneuvers were performed until it subsided. Patients continued follow-up visits until they were asymptomatic and the exam was normal.

Ninety-one consecutive patients were diagnosed with pBPPV. Sixty nine patients belonged to group 1 and 22 to group 2. The average age was just under 60 and the percentage of males was 22 in group 1 and 45 in group 2, which was significantly different. Additional significant differences included: 1. Symptom duration, in days, until diagnosis (43.2 in group 1 and 22.3 in group 2). 2. The fraction of patients requiring only one Epley maneuver in the first treatment session was 77.4% in group 1 and 23.4% in group 2.

The appearance of a torsional-geotropic nystagmus during RT is most probably due to pBPPV, with a more severe clinical presentation, requiring more Epley maneuvers than in patients with a negative RT. These patients had increased symptoms and were diagnosed earlier. However, the response to treatment was similar in both groups. It is most important to differentiate these patients in group 2 from patients with BPPV arising from the horizontal semicircular canal, which has different clinical features and is treated differently.