The first thing to examine after running the balance test is to look at the shape of the relative tests for shape and direction. The shape of the balance test result should be about 1.5:1 to 2:1 in the AP:ML directions. (This can be changed by foot placement and should be 1:1 if the feet are together – this will not necessarily match the normative data however) To ensure the best accuracy when testing balance and to get the best comparison to the normative data set have client’s heels on the inner border of the foot placement area on the Wii Balance Board.
AP direction greater than 2:1 = Ankle strategy to maintain balance. Can indicate a convergence/divergence problem, ankle instability or functional changes of the anterior cerebellar lobe associated with a rostral vermis syndrome (often nutritional component).
AP direction less than 1.5:1 = Hip Strategy to maintain balance. Associated with a much greater incidence of falls. Can result from truncal instability due to changes in vertebral, sacral, sacroiliac and hip alignment. Results from changes in the flocculonodular and posterior cerebellar lobes and associated with a caudal vermis syndrome.
Direction: The direction of the averaged sway paths as depicted by the ellipse overlay gives the major and minor directionality of the sway. As previously mentioned the major axis should be approximately 1.5:1 in size when comparing AP:ML sway directions. Look for any deviation of this direction, is the major axis orientated directly forward and back, or forward left and back right, or forward right and back left, or directly medial to lateral. Remember that forward right and back right movements are associated with the RIGHT vestibular system while forward left and back left are associated with the LEFT vestibular system.
To consider directionality further Limits of stability must be assessed, if there was a predominant sway direction for multiple tests, let’s say forward left and back right (right vestibular system) and there was a deficiency when doing the limits of stability testing back to the right then we could probably assume that there was a deficiency of the right posterior semicircular canal causing as it is associated in angular rotation back to the right. If the loss on limits of stability was forward left, then we would be thinking that the most likely cause is from a deficiency of the right anterior semicircular canal as this is associated with angular rotation forward to the left. If the limits of stability were normal or deficient in any other direction, then the clinical value of the sway direction is reduced.