Question
have a patient who has had a labyrinthectomy in one ear and continues to have many problems. Her physician has ordered an ENG and ABR on her to check the other ear. Will any valuable information be able to come from this? If so, what if any comparisons could be made?Answer
In this case, caloric testing in the other ear can reveal if the patient has function in that ear. If the total responses from warm and cool irrigations are less than 12 deg/sec, the patient has bilateral caloric weakness. One needs some form of rotation testing, either rotary chair or active head rotation, to determine if the bilateral caloric weakness is indeed indicative of a bilateral vestibular lesion.
The question does not specify the reason for labyrinthectomy but the procedure was used as a treatment for Meniere¡¦s disease in the 1980¡¦s. Some patients with Meniere¡¦s disease go on to develop Meniere¡¦s in the other ear. ENG can help with documenting the fluctuation of the vestibular function. Of course, caloric testing should be done in different occasions, before and during an active attack, to confirm such fluctuations.
In some destructive procedures such as vestibular neurectomy or Gentamicin therapy, residual function can remain in the involved ear. That is not very likely with labyrinthectomy but standard and ice water caloric testing can help with identifying any possible residual function in these cases.
Finally, presence of strong spontaneous nystagmus in ENG can indicate lack of vestibular compensation. The patient may benefit from exercises aimed at facilitating compensation.
Kamran Barin is the Director of the Balance Disorders Clinic at the Ohio State University, Department of Otolaryngology. He has taught national, international, and graduate level courses in vestibular function testing since 1983.
