Positional Downbeating Nystagmus : Tips from the Transitions

Kim, Ji Soo

Abstract

OBJECTIVE
: To describe transitions of positional downbeating nystagmus (PDN) to or from the benign positional vertigo (BPV) involving the posterior (PC) or horizontal semicircular canal (HC). BACKGROUND : PDN occasionally occurs during Hallpike maneuver, and has been ascribed to BPV involving the anterior semicircular canal (AC-BPV). Method : Of the 168 patients diagnosed as having BPV in the Dizziness Clinic of Cheju National University Hospital over the past 2 years, three showed transitions of PDN which occurred during Hallpike maneuver. All the patients received full neurotological examinations. The diagnosis of BPV was based on the typical nystagmus concurrent with vertigo elicited by positional maneuvers. The nystagmus was observed by using Frenzel glasses. Nystagmus was also analyzed by using a video camera or video-oculography, as needed. RESULT : Two patients initially presented with torsional downbeating nystagmus during Hallpike maneuver. The torsional component beat toward the uppermost ear. Both patients later developed the PC or HC type of BPV in the uppermost ear. Another patient developed torsional upbeating nystagmus during Hallpike maneuver, consistent with right PC-BPV, following a motor vehicle accident. After Epley maneuver, the nystagmus was transformed into PDN which was observed during Hallpike maneuver to either side and during central head hanging. During Hallpike maneuver, the PDN was more prominent when the involved ear was lowermost.
CONCLUSION
: These transitions suggest that AC-BPV may involve the uppermost or lowermost ear during Hallpike maneuver. In patients with AC-BPV, the direction of torsional nystagmus may play a crucial role in deciding the affected ear during Hallpike maneuver.