Diagnosis of bilateral posterior semicircular canal type of benign paroxysmal positional vertigo in a general ENT clinic

Abstract

　Because bilateral posterior semicircular canal (PSCC)-type benign paroxysmal positional vertigo (BPPV) is rare, this condition appears to be diagnosed and treated mostly in large hospitals. This report is aimed at underscoring the possibility of diagnosis of bilateral PSCC-type BPPV even in small general ENT clinics. From January 2015 to June 2017, at our general ENT clinic, we encountered two patients who showed right torsional and upward nystagmus in the right Dix-Hallpike (DH) maneuver and left torsional and upward nystagmus in the left DH maneuver. We recorded digital videos of their positional nystagmus during the right and left DH maneuvers. From the video recordings, we could analyze the positional nystagmus of one patient off-line in a three-dimensional manner. The rotational axis of the positional nystagmus in the right DH maneuver was perpendicular to the plane of the right PSCC and that of the positional nystagmus in the left DH maneuver was perpendicular to the plane of the left PSCC. The positional nystagmus in the other patient was analyzed off-line in a two-dimensional manner. During both the right and left DH maneuvers, transient upward nystagmus was observed. Thus, positional nystagmus could be observed upon excitation of the right PSCC in the right DH maneuver and upon excitation of the left PSCC in the left DH maneuver. Both patients were cured by Epley maneuvers. Therefore, we diagnosed both patients as having had bilateral PSCC-type BPPV. During the study period, we encountered 511 patients with BPPV. The ratio of bilateral PSCC-type BPPV to classical BPPV in the patients was 0.39% (2/511), indicating a very low incidence. Thus, by careful observation of the positional nystagmus in both right and left DH maneuvers, bilateral PSCC-type BPPV can be diagnosed even in a small general ENT clinic.