Towards theoretical understanding of pushing behaviour in stroke patients

"Pusher" is a term first introduced by Davies (1985) to describe a disorder where a patient "pushes strongly towards the hemiplegic side in all positions and resists any attempt at passive correction of posture" (Davies, 1985 p. 266). Davies indicated that "pushers" tend to have right-sided lesions, and that the severity of the disorder could vary. In the most severe cases, rehabilitation was severely compromised: the patient often failed to learn to walk even with assistance. In this review we attempt to address the complexity of the behaviour and to identify the causal mechanisms. Initially, we provide a general overview of the disorder by indicating what the characteristic features are, the incidence of the behaviour and current methods of measurement. Next, we address the issue of the postural control in general, reflecting on possible effects of unilateral brain damage on the ability to maintain a normal posture. Recent accounts of "pushing" behaviour have suggested a deficit in verticality perception and we explore the basis of this possibility with reference to relevant studies. Attentional deficits such as unilateral neglect have also been implicated in pushing behaviour. We consider whether it may not be more appropriate to consider motor rather than visual neglect. In particular, we introduce the concept of motor extinction and speculate on the role it may play in the genesis of pushing behaviour. We postulate that pushing behaviour may reflect the severe end of a continuum which may better be described as a right-hemisphere syndrome. We conclude with a discussion on implications for rehabilitation.