Timothy C. Hain, M.D. Last updated on: April 27, 2018
See "blunders". Also rotatory chair testing.
Suppression is recognized when the gains are low but the phases are normal. This means that the patient attempted to overcome their dizziness by fixating on something that was moving with their body -- perhaps their nose or hand. In essence, the patient refused to follow instructions, or the vestibular tester didn't instruct them at all.
It results in an abnormal rotatory chair result - -the gain is too low, but the phase is normal.
The suppression problem is generally seen when the technician is bored or tired, and forgets to keep the patient amused with tasks to keep their mind off of the rotation. It creates a pattern where typically gain is low at higher speeds. This is impossible for the vestibular system -- so it has to be something else (i.e. intention). Phase is generally normal it is impossible to control the timing of your eye movements with respect to a rotating chair.
We do not mean to imply that these people are purposfully attempting to "Fail" the rotatory test. While certainly possible, this is not very common. Suppression is more of a situation where the patient decides to do what is best for them at the moment, and ignore the instructions of the person running the machine.
Example 1 of suppression.
Example 2 of suppression. Note that the asymmetry is all over the place, and phase is slightly elevated. This patient might have a small amount of bilateral vestibular, but it is impossible to be sure due to the excellent suppression.
Methods of stopping suppression: