An electronystagmography evaluation shows that responses to right-warm/right-cool caloric irrigations are 12 percent weaker than left-warm/left-cool. How should this be reported?

• A. Unilateral weakness on the left
• B. Unilateral weakness on the right
• C. Directional preponderance to the right
• D. Normal caloric response

Answer: (D)

Caloric testing interprets the balance of responses between ears to decide if vestibular function is normal, or if there’s a unilateral weakness or a directional bias. A difference between the two ears needs to exceed a certain threshold to be considered clinically significant. In practice, a unilateral weakness (canal paresis) is typically flagged when the asymmetry is about 25 percent or greater. Here, the right ear responses are only 12 percent weaker than the left ear responses, which is below that cutoff and falls within normal variability.

Directional preponderance looks for a bias in the overall direction of nystagmus, not just a side-to-side drop in amplitude, and it’s usually considered significant only when the imbalance is sizable (often around 30 percent or more). Since the data don’t show a substantial directional bias, the result isn’t interpreted as directional preponderance either.

So the finding is reported as a normal caloric response.