Rotatory Chair Errors (see also blunders)
Timothy C. Hain, MD
Everyone makes mistakes.
Rotatory chair testing is complex and there are an immense number of errors that can occur. Some of these overlap with errors made during ENG testing (see this page for ENG errors).
- Wrong value for distance to eye calibration array. When there is a mismatch, there can be a peculiar pattern where mid-frequency VOR gain is too high.
- Light leak -- this causes too high gain at all frequencies, including low frequency. Phase is 0 at all frequencies.
- When there is a light leak during OKAN testing, there simply is no OKAN. Light leaks may be very subtle and still obliterate OKAN.
- Slip ring problem -- causes noise.
- Uncalibrated chair velocity, or uncalibrated OKN velocity. This can be spotted with the VVOR test as gain should be 1.0 at low frequencies.
- Suppression. Undistracted patient turns off their rotatory chair responses.