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ENG question

Tom Boismier boismier at umich.edu
Thu Sep 26 13:04:52 EST 1996


In article <3249F479.5CB0 at postoffice.worldnet.att.net>, 
Jenn.the.audiologist at POSTOFFICE.WORLDNET.ATT.NET says...
>
>I am going to post this on here first and maybe on asha-forum. Does 
>anyone know if hyperactive optokinetic responses (not OKAN)is indicative 
>of a central problem. For a 20 deg target the responses were approx. 50 
>deg (symmetrical) and for a 30 deg target they were about 70 deg 
>(symmetrical). I can find references to hyperactive OKAN but not OKN. 
>The sources only mention hypoactive responses for OKN. Thanks in 
>advance.

The most likely reasons I can think of are calibration error, and the patient 
sitting too close to the target. Barber and Stockwell have no mention of 
hyperactive OKN, and I've never seen it in 12 years of doing ENG. If the 
pursuit test is normal for age (assuming you're doing computerized ENG with 
age-matched norms), you are probably safe to ignore abnormal OKN. When you do 
OKN with a light bar (instead of a full-field stimulius like a rotary chair 
booth), you're probably stimulating pursuit pathways more than OKN pathways 
anyway. In fact, we don't routinely do OKN anymore in our lab. We will do the 
OKAN test for patients suspicous for mal-debarquement (sp?), but we only get 
that a few times per year.




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