Pusher syndrome and cortical graviception
When the cortex misreads upright, the body falls toward the lesion — and the SVV may not move with it.
What pusher syndrome is
After a hemispheric stroke (most often right parietal), a subset of patients actively push themselves toward the hemiplegic side, resist passive correction, and report that they feel upright when they are visibly tilted. This is contraversive pushing, distinct from the lateropulsion seen in Wallenberg syndrome. It is a disorder of the body’s perceived orientation in space, mediated by cortical graviception.
Expected SVV signature
| Cortical measure | Finding |
|---|---|
| Visual SVV (eyes open, dark surround) | Often normal or near-normal |
| Postural vertical (perceived body upright) | Severely tilted away from the lesion |
| Haptic vertical (tilting a rod with eyes closed) | Variably affected |
The dissociation between visual and postural verticals is the hallmark[7]. The patient sees correctly that a line is vertical but feels their body is upright while their trunk lies at 15–20° from earth-vertical. Visual SVV can be entirely normal in a patient with profound pusher behaviour — testing it alone will miss the diagnosis.
Visual vs postural — different graviceptions
The cerebral cortex maintains at least two estimates of vertical: a visual one (the perceived vertical of seen objects, measured by SVV) and a postural one (the perceived vertical of the body itself, measured by tilt-back paradigms). These are subserved by partially overlapping but distinct networks centred on the posterior insula, temporo-parietal junction, and somatosensory cortex[12].
Brainstem and peripheral lesions disrupt both verticals together — the patient sees and feels the same tilt. Cortical lesions can dissociate them.
Clinical relevance
Pusher syndrome is a major obstacle to stroke rehabilitation. Recognising it changes the rehabilitation approach: standard balance training reinforces the misperception. Effective therapy uses visual feedback (mirrors, vertical reference lines in the environment) to recalibrate the postural vertical against the intact visual vertical.
If a stroke patient resists being made upright but the bedside SVV (bucket) is normal, test postural vertical: tilt the patient passively in a chair and ask them to say when they feel upright. A 15° postural error with a 0° visual error is pathognomonic of pusher syndrome.
Companion findings
- Hemiparesis on the side toward which the patient pushes
- Hemisensory loss, often with neglect (right hemisphere lesions)
- Active resistance to passive correction toward true vertical
- Persistent contraversive head and trunk tilt