How is the vestibular system examined in a dizziness evaluation?

Updated: Jun 26, 2018
  • Author: Wayne T Shaia, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

Answer

The vestibular system is examined in a dizziness evaluation as follows:

  • Balance involves the overlapping function of several systems, namely, the visual system, the proprioceptive system, and the vestibular system. Together, these systems maintain equilibrium. Although many of the office-based tests incorporate this triad of sensory systems, most tests concern the vestibular system.

  • The primary goal of the vestibular system is to limit the slippage of images on the retina during head movement. Slippage of images greater than 2-3° per second blurs visual acuity. The 3 systems that are involved in limiting retinal slip are (1) the smooth-pursuit system, (2) the optokinetic system (which work best at relatively low head velocities), and (3) the vestibulo-ocular reflex (VOR) system. In the VOR system, the semicircular canals are angular accelerometers, and the otolithic organs are linear accelerometers. Because most human movements are brisk (0.6-8.2 Hz, or < 90° per second during walking to < 170° per second during running), the human vestibular system has evolved into a transducer of rapid head movement, an observation that is reflected in many of the tests.

  • For patients whose symptoms are episodic, physical examination findings may be normal between episodes. Furthermore, because the patient often can suppress nystagmus caused by a peripheral vestibulopathy, many of the vestibulo-oculomotor tests in the office examination are performed with +20 lenses (ie, cataract glasses), which prevent the patient from focusing on objects in the visual surround.


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