Are Monothermal Calorics Sufficient in ENG Testing?

Question

Answer

There are a few differing opinions on this subject. There is general agreement that a symmetrical monothermal test is very predictive of a normal bithermal test (about 97 to 99% predictive when using a narrow asymmetry value of 5% interaural difference (IAD)). One study used warm stimulus, another used both warm and cool and determined that cool was a better stimulus for a monthermal caloric screening test. The main problem with a monothermal screening is the high false positive rate. The most recent study to look at this found that 78% of patients failing the above 5% IAD had a normal bithermal test.

Bottom line: If for some reason (nausea, patient refusal, etc) you can't complete all four irrigations, and the monothermal responses are within 5% symmetry, you are likely to be okay (assuming your exam is otherwise normal). There is very little downside to completing all four irrigations, and the accuracy of your test is improved by doing so. Keep this in mind: Even with a 97% predictive value, 3 out of 100 patients will be misdiagnosed taking this shortcut.

Alan Desmond, Au.D is the director of Blue Ridge Hearing and Balance Clinic in Bluefield and Princeton, WV. Thieme Medical Publishers released his book Vestibular Function: Evaluation and Treatment in April 2004. He can be reached at Alan@earexperts.com