The terms from all four chapters – for quick reference, arranged alphabetically.
| Ampulla | Bulge at the end of each semicircular canal. It houses the cupula with the sensory cells, which translate the endolymph flow into nerve impulses. |
| Area gain | Gain computed from the areas under both velocity curves in the 0–100 ms window, that is, from the entire movement. Robust against brief disturbances. |
| Bilateral vestibulopathy | Bilateral dysfunction of the vestibular organ. The consensus criteria of the Bárány Society require a bilaterally pathological horizontal VOR gain below 0.6 in the vHIT. |
| Canal paresis | Loss of function of a semicircular canal. Clinically recognizable by a reduced gain in combination with catch-up saccades. |
| Catch-up saccade | Fast eye movement that recaptures the fixation target after the VOR has failed to move the eye sufficiently in the opposite direction. |
| Overt saccade | Catch-up saccade that occurs only once the head has come to rest. Visible to the naked eye – the clinical sign since 1988. |
| Covert saccade | Catch-up saccade that already takes place during the head rotation. Not visible to the naked eye; only video-oculography captures it reliably. |
| Crus commune | Common limb through which two of the three semicircular canals open into the vestibule. |
| Cupula | Gelatinous structure in the ampulla that is deflected by the endolymph flow and thereby bends the sensory hairs. |
| Gain | Ratio of eye velocity to head velocity. The ideal value of 1.0 means that the eye moves exactly as fast as the head, only in the opposite direction. |
| Instantaneous gain | Gain at a fixed point in time after impulse onset; 40 ms, 60 ms and 80 ms are commonly used. The two velocities are compared at exactly that moment. |
| Regression gain | Gain derived from a fitted regression. Usual variant: the slope in the plot of eye against head velocity over 0–100 ms. Variant according to Zamaro et al. (2020): the ratio of the two velocity-over-time slopes ±15 ms around peak head acceleration. |
| Head impulse counter | Display that fills up with every valid head impulse and thereby shows how many impulses have already been recorded. On Merlin the number of circles is configurable. |
| Head impulse test (HIT) | Bedside clinical examination, described in 1988 by Halmagyi and Curthoys. It captures overt saccades only. |
| Head orientation range | Sector in the impulse direction diagram that the head impulse has to fall within so that it runs in the plane of the canal pair being tested. When head position is correct it turns green. |
| Head zero position | Reference orientation of the head, set during the pre-test, to which the motion sensor of the goggles refers all subsequent head movements. |
| LARP | Left Anterior – Right Posterior: test plane of the left anterior and the right posterior semicircular canal. Head turned to the right, gaze straight ahead, head moved vertically up and down. |
| RALP | Right Anterior – Left Posterior: test plane of the right anterior and the left posterior semicircular canal. Head turned to the left, gaze straight ahead, head moved vertically up and down. |
| Oscillopsia | Apparent jittering of the surroundings with every head movement. Typical consequence of a failed VOR. |
| Pre-test | Check performed before the actual measurement: goggle fit, eye image (ROI, focus, brightness) and head zero position. Not part of the workflow bar. |
| Push-pull principle | The two semicircular canals of a pair work in opposite directions: what is excited on one side is inhibited on the other. Because inhibition ends at a discharge rate of zero, only a fast impulse reveals a deficit. |
| Reid's plane | Anatomical reference plane of the head used to orient the head for the measurement. |
| ROI (region of interest) | Analysis area in the eye monitor. It has to lie on pupil and iris, not on eyelashes or the lid margin. |
| Semicircular canal | One of three fluid-filled canals per inner ear that sense rotational accelerations of the head. The three canals are almost perpendicular to one another. |
| Vestibular nuclei | Relay station in the brainstem between the vestibular nerve and the ocular motor nuclei – the middle one of the three neurons of the reflex arc. |
| Vestibulo-ocular reflex (VOR) | Reflex that moves the eyes exactly counter to a head movement and thereby keeps the image stable on the retina. The fastest gaze-stabilizing system in humans. |
| vHIT | Video head impulse test. Validated in 2009 by MacDougall and colleagues; it allows each of the six semicircular canals to be tested separately. |
| Video-oculography | Video-based recording of eye movement. The basis of the vHIT and the prerequisite for detecting covert saccades. |
This training does not replace the instructions for use. The current instructions for use always apply; they are available online at hno.services in the knowledge base.
The key terms from all four chapters – from ampulla to vHIT.
Kommentieren ist für diesen Kurs nicht aktiviert.