Module 9
The clinical and laboratory tests of vestibular function — bedside examination, caloric testing, the video head impulse test, and VEMPs — and the specific anatomy each one probes.
Much of vestibular assessment needs no equipment at all. A structured bedside examination — watching the eyes, testing the reflexes, and provoking positional vertigo — can localise a lesion remarkably precisely.62
Caloric testing irrigates each ear with warm and cool water or air. The temperature change sets up a convection current in the lateral semicircular canal, driving the vestibulo-ocular reflex and producing nystagmus that can be measured.63
The video head impulse test, or vHIT, brings the bedside head impulse test into the laboratory. A lightweight goggle measures head and eye velocity precisely during small, fast head turns.19
The tests above probe the semicircular canals. Vestibular evoked myogenic potentials — VEMPs — are the way to test the otolith organs. A loud sound or vibration evokes a brief, measurable muscle reflex.30