Pusher Syndrome – a frequent but little-known disturbance of body orientation perception

Abstract

Disturbances of body orientation perception after brain lesions may specifically relate to only one dimension of space. Stroke patients with "pusher syndrome" suffer from a severe misperception of their body's orientation in the coronal (roll) plane. They experience their body as oriented 'upright' when it is in fact markedly tilted to one side. The patients use the unaffected arm or leg to actively push away from the un-paralyzed side and resist any attempt to passively correct their tilted body posture. Although pusher patients are unable to correctly determine when their own body is oriented in an upright, vertical position, they seem to have no significant difficulty in determining the orientation of the surrounding visual world in relation to their own body. Pusher syndrome is a distinctive clinical disorder occurring characteristically after unilateral left or right brain lesions in the posterior thalamus and -less frequently- in the insula and postcentral gyrus. These structures thus seem to constitute crucial neural substrates controlling human (upright) body orientation in the coronal (roll) plane. A further disturbance of body orientation that predominantly affects a single dimension of space, namely the transverse (yaw) plane, is observed in stroke patients with spatial neglect. Apparently, our brain has evolved separate neural subsystems for perceiving and controlling body orientation in different dimensions of space.

Posterior pusher syndrome — case report

“…Pusher syndrome is perceived as a little-known neurological disorder [5]. A critical appraisal of publications has been carried out, based on the PubMed database [14].…”

“…It is characterized by tilt (20-35 degrees) towards the contralesional paretic side [1][2][3][4][5]. Resistance to passive external correction of posture to an upright position is an important symptom of pusher syndrome [1][2][3][4][5].…”

“…), however, nonstroke causes have been described. The percentage of cases caused by right hemisphere lesions is 47%, with respect to 53% of the left hemisphere lesions [2,4,5]. Not all patients with lesions in the posterior thalamus, insula or postcentral gyrus areas demonstrated pushing behaviour.…”

“…Not all patients with lesions in the posterior thalamus, insula or postcentral gyrus areas demonstrated pushing behaviour. Patients with pusher syndrome maintain vestibular and visual functions [5]. The incidence of pusher syndrome is estimated to be between 10 % and 27% [6], but the number of misdiagnosed cases is not known.…”

New Insights for a Better Understanding of the Pusher Behavior: From Clinical to Neuroimaging Features

“…Karnath et al found 5 patients with severe PB (SCP=6) who experience their body as being oriented "upright" when it is actually tilted about 18° towards the side of the brain lesion and with no SVV bias (Karnath et al, 2000b). According to the authors, the possible explanation for the PB is that when patients try to move their body to a subjectively 'upright' position, they became laterally unstable because their center of mass was shifted too far to the ipsilesional side and they react to this imbalance by pushing themselves to the contralesional side (Karnath et al, 2000b;Karnath, 2007). In contrast, Pérrenou et al recently found a contralesional bias of SPV in 6 pusher patients with an SCP score ranging from 3 to 6.…”