Perception of verticality after recent cerebral hemispheric stroke

Area of Science:

• Neuroscience
• Ophthalmology
• Neurology

Background:

• Cerebral hemispheric lesions can alter subjective visual vertical (SVV) perception.
• SVV disturbances may relate to balance issues, but effects of visual field defects and lesion location remain unclear.

Purpose of the Study:

• To assess SVV perception in patients with recent hemispheric stroke.
• To investigate the relationship between SVV perception, visual field defects, visuospatial neglect, and lesion site.
• To examine SVV perception with the head upright and tilted.

Main Methods:

• Forty hemiplegic patients (20 left, 20 right stroke) underwent neurological examination, visual field testing, and visuospatial neglect assessment.
• Lesion site was determined by CT scan, focusing on the vestibular cortex.
• Subjective visual vertical was tested by adjusting a luminous rod in a dark room, with repeated measures for binocular/monocular vision and head positions (upright, tilted).

Main Results:

• 57% of patients showed abnormal SVV deviation, significantly greater than controls.
• SVV deviation was strongly correlated with visuospatial neglect, not lesion location.
• The 'E' effect (SVV shift opposite to head tilt) was absent in patients when tilting the head toward the nonparetic side.

Conclusions:

• Recent hemispheric stroke significantly affects SVV perception, with a strong correlation to visuospatial neglect.
• The 'E' effect's absence in hemiplegic patients suggests mediation by neck somatosensory structures, potentially due to stretching.