Vestibular recruitment?

Tom Boismier boismier at
Mon Mar 4 08:29:43 EST 1996

>Does vestibular recruitment actually exist? I have seen several patients
>with  seemingly hypersensitive vestibular systems. Caloric irrigations
>produce nystagmus with SSCs of over 80. I say "over" because the maximum
>measurement my ICS system will measure is 80. Is this significant? Is it
>indicative of pathology?

In our experience, the most common reasons for hyperactive caloric responses 
are (in no particular order): 

calibration error;

a highly-alerted (i.e. anxious...) patient, who panics when symptoms start; 

stimulus error (irrigation time too long, temp too high or low, pressure too 

middle aged patient with hydrops or Meniere's. Studies have reported increased 
SPV of caloric responses in middle age, and in hydrops patients. When you 
combine the 2 factors, it can be pretty impressive.

A true hyperactive response (with the above ruled out) weakly suggests CNS 
involvement, localizing to vestibulocerebellum. I would want confirmation from 
abnormal pursuit ocularmotor testing and/or increased gains on rotary chair 
before I made a big deal of it though...

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