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Sensory selection pattern

Sensory selection pattern

Figure 8.6. Illustration of the six conditions of the CTSIB (a). Patterns of sway in healthy subjects (open bars) and subjects with vestibular loss, visual dependence, and sensory selection problems (black bars) are shown in (b) (adapted from Black et al., 1988).

Surface dependent pattern

Figure 8.6. Illustration of the six conditions of the CTSIB (a). Patterns of sway in healthy subjects (open bars) and subjects with vestibular loss, visual dependence, and sensory selection problems (black bars) are shown in (b) (adapted from Black et al., 1988).

lesions such as multiple sclerosis (MS), head injury, and stroke, and some patients with vestibular pathology leading to increased visual dependence may have difficulty with these conditions. Figure 8.6 (adapted from Black et al., 1988) shows the patterns of sway in control subjects and patients with various sensory organization problems.

Clinical assessment of sensory organization should also include evaluation of the person's perceived limits of stability (by asking them to lean in all directions without moving their feet) and postural vertical (by assessing their standing and sitting postural alignment with respect to gravity with and without vision and on an unstable surface). Postural stability and strategies may be affected similarly whether a patient's perceived or actual limits of stability are small or distorted. Patients with somatosensory loss in the feet show reduced limits of stability in standing whereas patients after some strokes or unilateral vestibular loss may show asymmetrical limits of stability (as well as a tilted postural verticality).

One should also consider the role of extrinsic factors in balance control. It is important to recognize that people must balance in a variety of environments in the community and the home. Extrinsic factors that may contribute to balance problems include slippery, wet, uneven, and cluttered surfaces and stairs. Lighting can also greatly influence balance, as improper or inadequate lighting can reduce the usefulness of visual inputs (Birge, 1993).

Balance assessment is complex because balance control is multifactorial. In addition to the factors mentioned above, there are many others. For example, elderly individuals who are taking psychoactive medications, or more than four medications, are twice as likely to fall when compared to those not taking these medications (Cumming, 1998). Current clinical instruments have been developed to predict whether patients are at risk for falls rather than to determine the underlying reason for the balance problems. Review of these balance instruments is beyond the scope of this chapter (see Allison, 1995; Whitney et al., 1998, for more information).

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