[Apraxia of gait and disorders in posture and locomotion]

Apraxia of gait is a unique disorder of locomotion characterized by inability in lifting the feet from the floor despite alternating stepping action (frozen gait), and disequilibrium. Responsible site of lesions are in the frontal lobe and/or the basal ganglia. It is observed in an advanced stage of Parkinson's (PD) or vascular parkinsonism with multiple cerebral infarction (MCI). Studies on equilibrium and natural gait have disclosed unique features in this condition. Records of floor reaction forces in forward locomotion showed that vertical-foreaft vector angles at kick-off phase is small in both PD and MCI with frozen gait. EMG of antagonists in leg muscles were either reciprocal or coincided in frozen gait, and rhythm of stepping was crucial for development of freezing. Center of foot pressure (CFP) in forward-bent natural posture in PD still locates behind that of normals. For voluntary forward bending, maximal shift of CFP was smaller, and increase in EMG was larger in PD subjects. Pushing chest backward results in step-out or fall in parkinsonians. In this response, EMG in the pretibial muscles were the same amount in both PD and normals. However, velocity in hip extension and amount of knee and ankle displacement were smaller in PD.