All audiologists and ENT specialists are aware that asymmetrical hearing loss should be considered as potential auditory nerve pathology until proven otherwise. In fact, the American Academy of Otolaryngology-Head and Neck Surgery lists it as a position statement on their website as “Red Flags-Warnings of Ear Disease.”
The standard of care for asymmetrical hearing loss is either to perform an Auditory Brainstem Response (ABR) test, or to order an MRI of the internal auditory canals. To do otherwise might be considered negligent. For more detail on this topic, click here
So, if asymmetrical hearing loss is a trigger to further investigate auditory nerve pathology, how shall we view asymmetries on caloric testing or rotational chair testing? Is it reasonable and affordable to order an MRI exam on every patient with an asymmetry? Is an ABR exam a reasonable substitute? Although we know that MRI is more sensitive than ABR for detecting small (less than 1-cm ) tumors, is an ABR sensitive enough to detect tumors that are large enough to create an asymmetry on vestibular testing?
A recent study reports that ABR is almost 96% sensitive in detecting tumors greater than 1 cm, and the authors recommend ABR as a more cost-effective screening than ordering more expensive MRI scans for these patients. However,
We do ABR testing routinely on patients undergoing comprehensive vestibular evaluation. While most of these are normal, we have detected acoustic neuromas (confirmed through MRI) on several patients that would have been missed otherwise.
I don’t think there is a set standard, so I hope we have some commenter’s offering their own experience and opinions.
Photo courtesy of http://www.babyhearing.org/hearingamplification/hearingloss/testsexpect.asp