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LEARNING OBJECTIVES
Upon completion of this chapter, the reader will be able to:
Describe the standardized and nonstandardized tests and measures used to identify impairments in body functions and structures, functional limitations, and participation restrictions for an individual with a diagnosis of vestibular dysfunction.
Integrate information regarding pathophysiology, diagnostic criteria, and potential differential and associated diagnoses to develop a prognosis for individuals presenting with symptoms of dizziness, imbalance, and/or motion intolerance.
Select appropriate tests and measures to assess impairments and functional limitations associated with vestibular dysfunction.
Develop an evidence-based plan of care to maximize outcomes for an individual with the diagnosis of vestibular dysfunction.
Identify appropriate referrals for individuals with a diagnosis of vestibular dysfunction.
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For the human balance system to function at its most efficiently, it relies on contributions from proprioceptive, visual, and vestibular components. The vestibular system is composed of central and peripheral components that provide information necessary for spatial orientation.
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Information regarding the estimation of head orientation is sent from the peripheral nervous system to the central vestibular system, where it is processed and output is provided to the ocular muscles and spinal cord. Three primary vestibular responses result from this output. The vestibulo-ocular reflex (VOR) stabilizes visual images on the fovea. This reflex allows vision to remain clear when the head is in motion. Should the VOR be impaired, complaints of double vision or dizziness may occur (Figure 13-1). The vestibulospinal reflex (VSR) helps to maintain postural stability, especially during head movement. When the VSR is affected injury, an individual may be observed to lean toward the side of involvement. This posture results from unilateral input regarding head position from the uninjured side. The vestibulocollic reflex (VCR) works to maintain head position on the neck by stabilizing the neck muscles. The VOR works closely with the VCR. Should the VOR not work adequately to stabilize visual images, the VCR may become overactive in an attempt to limit head movement.
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Peripheral Components
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The peripheral vestibular system (Figure 13-2) is made up of a membranous labyrinth housed in each of the 2 temporal bones. Each labyrinth contains 3 semicircular canals. These organs detect the angular acceleration of the head in space and are filled with endolymph that moves freely in response to head rotation and tilting. These 3 canals are oriented in a (1) horizontal, (2) anterior, and (3) posterior orientation and are labeled according to that orientation. The left and right anterior and posterior canals have a more vertical orientation, so there is greater redundancy in the information received from head movement ...