Over the next couple of weeks, I will provide descriptions of the components of the Videonystagmography evaluation. These are samples of descriptions used to familiarize physicians and other health care professionals with each procedure. There is some overlap because the placement of video goggles and calibration is the same for the different procedures, so I will condense that portion in future posts.
92541 – Gaze and Spontaneous Nystagmus Test: It is common to have patients refrain from medications used to treat dizziness, nausea, pain, anxiety or depression prior to vestibular testing, as they can falsely suppress vestibular responses. Before testing, the examiner must question the patient regarding any medications that may affect test results. The patient must also be questioned regarding current symptoms, as vestibular disorders are not static, but rather typically occur episodically. The patient must also be questioned about visual status, prior history of known eye mobility issues, and a quick visual scan of eye range of movements and symmetry.
The patient is instructed to sit quietly during this test. Goggles with cameras illuminated by infra-red lighting are placed on the patient. The darkest spot of the eye, the pupil, is tracked by the software, so a tracking threshold must be established. Once tracking is established, a calibration procedure begins where the patient is asked to visually track a moving target which travels over fixed parameters (or degrees), in order to quantify any existing nystagmus.
Initially, the eyes are viewed with gaze directed forward, then the patients is instructed to gaze laterally to the right, then left. This process is performed both with visual fixation (either leaving one eye uncovered or using a fixation light inside the goggles), and without visual fixation as most labyrinthine nystagmus are suppressed if the patient is not in total darkness. The examiner must make a judgment regarding physiologic endpoint nystagmus and pathological nystagmus, must delete artifact such as eye blinks from the recorded data, and measure the slow phase velocity of any pathologic nystagmus.