Once patients tolerate the X1 viewing paradigm, they can then progress to the X2 viewing paradigm, where the patient’s head and the target are moving together in opposite directions. In this exercise, the patient holds the card with the letter target at arm’s length and moves the card and the head from side to side in a small trajectory in opposite directions, maintaining a clear focus on the image. As with X1 viewing, the patient performs this exercise 3 to 5 times per day for 1 minute, as fast as possible while still maintaining a clear focus, eventually working up to 2 minutes. This exercise can be progressed to standing, and then standing with a complex visual background as in the X1 viewing exercise. and to the edges of the BOS of varying diameters. Activities that displace the COM, such as reaching, lifting, raising the arms overhead, shifting weight acceptance from leg to leg, and multidirectional walking all utilize anticipatory postural control. The patient’s balance must be challenged in order for physiological changes to take place. Increasing the direction, degree, and smooth control of COM excursion and reducing reliance on external support are important components of anticipatory postural control training. Reactionary postural control refers to postural adjustments that are made in response to unexpected perturbations. These postural adjustments are stereotypical movement strategies known as ankle , hip , and stepping strategies, mediated by synergistic muscle activation patterns. The CNS uses information from sensory inputs and muscle stretch receptors about quick unplanned movement to elicit a reflexive response. The particular strategy employed is based on the surface conditions, direction of movement, and the degree of loss of balance. An ankle strategy will be employed during small amplitude movements while standing on a firm surface, creating a net inverted pendulum movement over the ankles to maintain vertical orientation of the body with respect to gravity. An example of this would be standing on a slowly moving train. A hip strategy will be elicited when an ankle strategy is not sufficient, such as when there is a large anterio-posterior displacement of COM, or when the surface conditions are not conducive to utilizing an ankle strategy (standing on a narrow or compliant surface). In this case, the person will exhibit a forward and backward sway of the trunk over the hips. A stepping strategy is elicited when a large amplitude or velocity of movement brings the COM outside of the BOS, necessitating a step to restore the BOS under the COM. This is what happens when the train makes an abrupt stop or acceleration (Shumway-Cook & Woollacott, 2011). For example, the patient with impaired somatosensation due to peripheral neuropathy will require both visual and vestibular information for postural control. Patients with profound vestibular loss rely on somatosensory and visual inputs to compensate for loss of vestibular inputs. Under these circumstances, the treatment program takes on an accommodative approach, rather than a restorative approach, training increased use of visual cues for postural control in the absence of effective vestibular inputs. In these cases, the patient should have full use of visual inputs, performing activities with eyes open and in well-lit environments, and not be placed in conditions 3 or 4 of the mCTSIB (eyes closed, standing on floor; eyes closed, standing on foam, respectively) as a rehabilitation approach.
movement to perform the activity for the full minute. The tempo should also be reduced if the patient experiences any extreme nausea or dizziness. This should be performed at least 3 times with a 1-minute rest between to allow symptoms to resolve to baseline, at minimum 3 times per day, for a total of at least 12 minutes per day (Hall et al., 2016). Care should be taken not to increase the patient’s dizziness so that it becomes persistent for greater than a few minutes. The goal is to work up to 2-minute increments. This activity can start in a sitting position, and when able, progress to a standing position. The level of challenge can also be increased by having the patient perform the activity with the target taped to a blank wall 6 feet away, and then adding a visually complex field, such as a checkerboard, on the wall while the patient holds the card at arm’s length. Balance retraining A problem-oriented approach to balance retraining should be directed at the particular areas of postural control that were found to be impaired on examination and through the patient subjective report. Postural control is achieved through the interplay of input and interpretation of sensory afferent information from visual, somatosensory, and vestibular systems, with effective motor output. Balance retraining should take into account: ● Addressing static, anticipatory, and reactionary postural control. ● Increasing the excursion of the center of mass in all directions in sitting and standing. ● Walking in various environmental contexts such as busy environments, over different surface conditions such as compliant and uneven surfaces, and in multiple directions. ● Adding a cognitive task to increase the challenge (split attention) and train mobility in a functional context; and ● Altering the reliance on visual and somatosensory inputs. The aim of static postural control is to maintain the center of mass (COM) within the base of support (BOS). The larger the BOS, the more easily static stabilization is achieved. Static postural control training should incorporate techniques, such as manual resistance in alternating agonist-antagonist muscle groups, that facilitate smooth coordination of agonists and antagonists. The aim is to create muscle co- contraction around a joint or body segment in sitting and standing, leading to stable holding of positions. Dynamic postural control includes both anticipatory and reactionary strategies. Successful dynamic postural control requires that sensory inputs provide accurate information about movement through space to allow the CNS to create an effective motor plan to maintain balance. Training anticipatory postural control requires maintenance of upright orientation during movement of the COM within Sensory integration training The conditions under which the patient exhibits difficulty maintaining postural control on the mCTSIB can guide treatment by providing insight into which sensory cues the patient relies upon and may not be utilizing effectively. The patient with vestibular dysfunction will tend to rely on other sensory inputs for postural control, with reliance on vision the most predominant. Altering sensory cues by having patients close their eyes or stand on a compliant foam surface will systematically reduce reliance on vision and somatosensation, respectively, to drive more effective interpretation and utilization of vestibular inputs to maintain balance. However, the clinician must take care not to alter sensory inputs on which the patient is reliant due to damage to other sensory systems caused by injury or disease.
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