Identifying cases of non-organic vertigo using dynamic posturography

Based on observations of normal subjects mimicking a balance disorder, a classification procedure was developed to objectively identify the responses of subjects with non-organic vertigo to dynamic posturography. The stimulus was a dorsi-flexion-inducing rotation of the support surface on which the subject stood. Responses were categorised as either normal or one of three non-organic response types (mimicked balance disorder): intentional rotation of the trunk too far forward or too far backward, or a pendulumlike movement that allowed the trunk and legs to fall backwards. The response variables which, when combined in a linear fashion, provided an optimal separation of the response types were, in order of significance: paraspinal EMG activity 240 ms after stimulus onset, trunk pitch-angular-velocity at 350 ms, upper-leg angular velocity at 500 ms and trapezius EMG activity between 120 and 220 ms. When this technique was applied to the responses of patients suspected of non-organic vertigo from Romberg tests, the majority were classified as belonging to the backwards response type, the remainder into the pendular or forwards response type. The classification procedure represents a new technique for reliably identifying non-organic forms of vertigo using objective criteria.