Laboratory testing of the vestibular system

Recent reports on vestibular testing, relevant to clinical diagnosis, are reviewed.Besides the case history and bedside examination, objective measurement of the vestibuloocular reflex in all of its facets remains the cornerstone in the diagnostic process.

In recent years, this has been enhanced considerably by reliable unilateral tests for the otolith organs, most notably by vestibular-evoked myogenic potential recording and estimation of subjective visual vertical. In addition, progress has been made in the investigation of multisensory interaction, involving visual acuity and posturography.Technological developments include improved eye movement measurement techniques, electrotactile and vibrotactile sensory enhancement or substitution, the use of virtual reality devices and motion stimulators such as hexapods and the rediscovery of galvanic vestibular stimulation as a research and diagnostic tool.

The recent introduction of new tests, together with the development of novel technologies, is gradually increasing the scope of the physical and bedside examination of the dizzy patient (see chapter 'Medical management of peripheral disorders' in this issue). The use of more complex equipment, such as rotating chairs, linear sleds, hexapods and posturography platforms, is likely to become limited to specialized laboratories and rehabilitation centers in future years. Further, high resolution magnetic resonance tomography (MRT) and computed tomography have allowed insight into the morphology and determination of malformations of the human labyrinth.