Body representation after a stroke in the brainstem

Lesion occurring in the brainstem may cause a postural tilt and balance disorders, which could be due to an inaccurate perception of the body orientation. The objective of this study was to determine the effects of a brainstem stroke on body representation in horizontal and frontal plane, and links with impaired posture and neuroanatomy.

Forty patients with stroke in left brainstem (L-BS) or right (R-BS) were compared with 15 matched control subjects (C). The subjective straight-ahead (SSA) was investigated using a method disentangling lateral deviation and tilt components of error.

The L-BS patients had contralesional lateral deviation of SSA. In addition, they showed an ipsilesional tilt, more severe for the trunk than for the head. By contrast, in R-BS patients, the representation of the body midline was fairly accurate in both the horizontal and frontal planes and did not differ from that of control subjects.

This work highlights an asymmetry of representation of body associated with left brainstem lesions extending to the right cerebral hemisphere. This deviation appears only after a left lesion, which may point to a vestibular dominance. These results open a new perspective of neuro-rehabilitation of postural disorders after a stroke, with the correction of the representation of body orientation.