This study evaluates the diagnostic sensitivity of a simple method of producing bidirectional cupular deviation using a monothermal stimulus. This stimulus has the advantage of conservation of time and increased patient comfort and acceptance (two caloric irrigations instead of four). Each patient was seated with his head extended 60° during the caloric irrigation. Eighty seconds after the onset of irrigation, the patient placed his head forward, thereby causing both an ampullopetal and ampullofugal flow of endolymph. Right/left difference and directional preponderance were computed for both monothermal warm and monothermal cold irrigations and compared to the traditional bithermal caloric results. This study comprised a control group of 13 normal patients and 144 dizzy patients.
False positive (abnormal monothermal but normal bithermal) and false negative (normal monothermal but abnormal bithermal) tests occurred in 45 percent and 50 percent of examinations, respectively. Inaccurate measurement of the weak slow phase velocity that usually accompanies the inverted position was a probable cause of the poor correlation between test results since a separate analysis of electronystagmograms with more intense nystagmus in the inverted position resulted in an improved correlation. Further evaluation of this technique should include methods that result in.more accurate measurement of slow phase velocity.