6.SUPPRESSIVE HEAD IMPULSE PARADYME
6.SUPPRESSIVE HEAD IMPULSE PARADYME
The patient’s gaze must follow the moving laser pointer while the examiner rapidly moves their head to the right or left (acceleration 4,000 to 8,000°/sec). If the vestibular system function is normal, the vestibular ocular stabilization reflex causes the eyes to move in the opposite direction to the head movement (horizontal vestibular ocular reflex). The patients have to produce a catch-up saccade to keep their gaze on the laser. Conversely, if the vestibular system is not working, the eyes remain still and look at the laser target. The examiner will not see any saccade.
In normal patients, the head impulse generates a catch-up saccade to look at the laser target regardless of which way the head is turned.
In conclusion, this test provides important information about residual vestibular function and the potential use of the saccade system to compensate for the defective vestibular system. It may be useful in patients suffering from oscillopscia (i.e. oscillations in the visual field caused by head movement).
In patients with a left reflex deficiency, the head impulse does not generate a catch-up saccade.
Preparation
Do not wear mascara or eye-liner since these interfere with pupil tracking.
Time taken: 10 minutes.