Identification of non-organic instability by sway magnetometry

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Abstract
This paper describes the application of sway magnetometry, which objectively measures stability, to assist in the identification of non-organic instability. Three subject groups were studied; 14 normal subjects, 14 subjects with organic dizziness, and 19 subjects assessed as having possible non-organic dizziness before further clinical investigation. Eight of these 19 were subsequently classed as having non-organic dizziness on grounds of their history, clinical examination and standard audio-vestibular investigations. Movement in the horizontal plane at the hips was measured by sway magnetometry in each subject. The absolute and percentage change in path length and area were determined for 15 s before and 15 s after the subject was informed that the test was starting. For absolute path length and area, five out of the eight subjects with non-organic dizziness showed an increase in sway above the upper limit of normal, while only one out of the other 11 subjects in the group showed such an increase (P <0.02). None of the subjects in the normal or organic group exceeded the upper limit of normal when results were expressed as absolute change in path length or area. Sway magnetometry can provide valuable data to assist the clinician in identification of non-organic dizziness.