Affiliations: [a] Neuro-otology Unit, Vancouver General Hospital, Vancouver, Canada | [b] University of British Columbia, Faculty of Medicine, Division of Otolaryngology, Vancouver, Canada
Correspondence:
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Corresponding author: A. Mallinson, Neuro-otology Unit, Vancouver General Hospital, 4{th} Floor – Diamond Centre, 2775 Laurel St., Vancouver, B.C., V5Z 1M9, Canada. Tel.: +1 604 875 4005; Fax: +1 604 875 4526; E-mail: art@mallinson.ca
Abstract: Introduction:Electronystagmography (ENG) testing has been supplanted by newer techniques of measuring eye movement with infrared cameras (VNG). Most techniques of quantifying caloric induced nystagmus measure the slow phase velocity in some manner. Although our analysis is carried out by very experienced assessors, some systems have computer algorithms that have been “taught” to locate and quantify maximum responses. We wondered what differences in measurement might show up when measuring calorics using different techniques and systems, the relevance of this being that if there was a change in slow phase velocity between ENG and VNG testing when measuring caloric response, then normative data would have to be changed. There are also some subjective but important aspects of ENG interpretation which comment on the nature of the response (e.g. responses which might be “sporadic” or “scant”). Methods:Our experiment compared caloric responses in 100 patients analyzed four different ways. Each caloric was analyzed by our old ENG system, our new VNG system, an inexperienced assessor and the computer algorithm, and data was compared. Conclusions:All four systems made similar measurements but our inexperienced assessor failed to recognize responses as sporadic or scant, and we feel this is a limitation to be kept in mind in the rural setting, as it is an important aspect of assessment in complex patients. Assessment of complex VNGs should be left to an experienced assessor.
