The three semicircular canals of a labyrinth are almost perpendicular to one another. That is precisely why the three test planes lateral, LARP and RALP can stimulate each individual canal separately. This spatial arrangement is hard to grasp from a drawing – on the model it becomes immediately visible.
Drag to rotate · scroll to zoom · two fingers to pan. Without interaction the model rotates by itself.
What to look for
- The three semicircular canals are shown in separate colors, the vestibule and cochlea in bone color. The colors serve only to distinguish them and have no anatomical meaning.
- The three semicircular canals are almost at right angles to one another in pairs – between about 71° and 83° in this model.
- Two of the canals open into the vestibule together through the crus commune; that is the conspicuous Y-junction on the model.
- Each canal ends in a bulge, the ampulla. It houses the cupula with the sensory cells that register the endolymph flow.
- The large spiral structure is the cochlea. It belongs to the organ of hearing and plays no role in the head impulse test.
- The counterpart on the other side of the head is built as a mirror image. This mirror symmetry gives rise to the push-pull principle: what is excited on one side is inhibited on the other at the same moment.
The model is for spatial orientation. The individual canals are distinguished by color but deliberately not labeled, and the model is not marked as a left or a right labyrinth – for assigning the test planes, only the illustration in Chapter 1 applies.
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.
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