Pusher syndrome

pusherPatients with the pusher syndrome are characterized to push toward the weak side of the body, generally the left side (on a coronal plane) after a right hemisphere lesion. This behavior puts them at high risk of falling. These patients resist to the examiner’s attempts of rectifying the correct orientation by pushing the body with the unaffected limbs toward the affected ones, generally on the left. A rarer « posterior » variant has been reported in which patients push posteriorly on a sagittal line.
The pusher syndrome occurs in patients with acute right hemisphere stroke. It is less frequent with other brain diseases (tumors, multiple sclerosis).
Rehabilitation of such patients could be challenging as the pusher syndrome appears the effect of a reflex behavior and the patients seem resistant to learn compensatory strategies. Patients with the pusher syndrome have longer times of rehabilitation in comparison to other stroke patients.
Several scales are adopted in clinical studies to establish a diagnosis of the condition and to grade its severity (the Pusher index, the Melbourne Index Scale, the Scale for Contraversive Pushing, the Lateropulsion Scale). However, on a clinical perspective, the condition of the Pusher syndrome should be considered just when the patient is observed pushing constantly on one side, no matter in what position he is (standing, sitting or lying). The patient with the pusher syndrome pushes almost always toward the left side of the body and the syndrome is almost always associated, at least as I observed in my profession, with signs of left spatial unilaterl neglect (the condition of ignoring the left side of the body in several sensory modalities).
The brain areas that can be damaged in patients with the Pusher Syndrome overlap with those that are associated with spatial neglect. Probably for the pusher syndrome, the damage of parietal thalamo-cortical connections is most relevant.
The ultimate mechanism of the pusher syndrome could be an incorrect perception of the verticality of the body because of two combined conditions: a loss of sensory stimuli from the affected side and the presence of left spatial neglect. In this perspective, the pusher syndrome has been called also « graviceptive neglect ».
Our perception of the gravity line of the body is constructed on the base of visual (the visual surrounding) and sensory stimuli (proprioceptive, haptic and vestibular body inputs) and it can be studied in a dark room by dissociating and manipulating experimentally the different stimuli. The pusher syndrome should be studied in the Space in the absence of gravity.
Rehabilitation programs should assess and recenter the body gravity line by adapting the patient’s movements and posture to all the sensory modalities, although there is, as usual, some controversy as per the sensory modality to prefer.

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