12. 重心動揺検査の臨床学

抄録

　Postural instability occurs in some patients, and could be caused by a wide range of disorders, including neurological diseases, vestibular, visual and/or somatosensory dysfunctions, and musculoskeletal impairments. Problems in postural balance are commonly evaluated by posturography. Posturography is based on the principle of measuring changes in the center of pressure (COP), which represents the center point of the entire pressure exerted by the foot-ground contact surface on the force plate.

　Graphical representations called stabilograms and statokinesigrams are commonly obtained by measurement of the body sway using posturography. Stabilograms depict the time series of the COP displacement in either the anteroposterior or mediolateral direction, while statokinesigrams show the bidimensional COP trajectory on the ground extracted by the COP plot. Parameters derived from the COP trajectories to assess the patients' capabilities and performance to keep their balance include the sway path (cm), sway area (cm²), RMS (root mean square), and the Romberg quotient. A 0.2-Hz postural sway is a characteristic finding in unilateral vestibular disorders. Patients with anterior cerebellar lesions manifest a characteristic increase in sway activity in higher power spectra frequency bands, with a typical peak between 2 and 4Hz. Higher values of the Romberg quotient for variables of the sway path and area are seen in patients with vestibular or proprioceptive dysfunction. Posturography could assist in the differential diagnosis of balance disorders, and is a useful tool to evaluate the degree of postural imbalance and the effects of therapeutic interventions.

　Although the usefulness of posturography for the differential diagnosis of some diseases presenting with dizziness and balance disorders remains limited, several recent technological developments may offer the promise for improved diagnostic precision.