Question
I have been doing ENG for many years using strip chart recorders, and have just switched to VNG. On rare occasions I saw downbeating nystagmus, and more frequently, upbeating nystagmus. Are there times vertical nystagmus would be normal?
Answer
VNG testing allows us to record eye movements in much greater detail than ENG testing, so it is understandable to have some initial uncertainty about how to interpret the responses. Just as for horizontal nystagmus, a certain amount of vertical nystagmus is normal when vision is denied (goggles closed). A recommended normative cutoff for this vertical positional nystagmus is 7 degrees per second when vision is denied (Kamran Barin, personal communication). Significant vertical nystagmus that is present when vision is denied should be reported as a non-localizing finding. Also similar to horizontal nystagmus, when vertical nystagmus is recorded with vision, it is generally considered to be significant. When present during gaze or positional tests with vision, the presence of vertical nystagmus is a central finding.
Amanda Cerka Mroz received her B.A. in Communicative Disorders from the University of Northern Iowa and her M.A. in Audiology from The University of Memphis. She joined GN Otometrics in January 2007 as a Professional Trainer. In this role, she develops educational materials and programs, collaborates with product managers, and provides audiological support for customers.