Hemispatial neglect is a failure to attend to, represent, or act upon stimuli located in the contralesional side of space, despite intact primary sensory and motor function. First described by Heidenhain in 1919[1], neglect is now recognized as a common and disabling feature of corticobasal syndrome (CBS). The characteristic asymmetric cortical involvement in CBS, particularly affecting the right hemisphere's parietal lobe, creates a predilection for left-sided neglect[2].
Unlike the primarily subcortical pathology in conditions like progressive supranuclear palsy (PSP), CBS involves the cortical mantle directly, particularly the inferior and superior parietal lobules, leading to more frequent and severe neglect syndromes.
| Region | Function | CBS Involvement |
|---|---|---|
| Inferior Parietal Lobule (IPL) | Spatial attention, reorienting | Primary target |
| Superior Parietal Lobule (SPL) | Spatial representation | Variable involvement |
| Posterior Parietal Cortex (PPC) | Visuospatial processing | Almost always affected |
| Superior Temporal Gyrus | Multimodal integration | Often co-affected |
| Frontal Eye Fields (FEF) | Oculomotor control | Involvement common |
| Basal Ganglia (Putamen) | Attention shifts | Subcortical component |
The dominant theory of neglect involves a disruption of the "attentional gradient" or "spatial priority map" in the right hemisphere. The right hemisphere is thought to maintain vigilance over both hemispaces (bilateral attention), while the left hemisphere attends primarily to the right hemispace. In CBS:
| Feature | Description | Prevalence in CBS |
|---|---|---|
| Left inattention | Failure to respond to stimuli on left side | 25-40% |
| Hemisensory loss | Reduced awareness of left-sided sensation | 30-50% |
| Oculomotor neglect | Difficulty initiating leftward saccades | 35-50% |
| Motor neglect | Underutilization of left limb despite strength | 20-35% |
| Test | Purpose |
|---|---|
| Behavioral Inattention Test (BIT) | Comprehensive neglect battery |
| Catherine Bergego Scale (CBS) | Functional neglect assessment |
| Line Bisection Task | Basic neglect screening |
The presence of neglect in CBS indicates:
Heidenhain A. Uber progressive Hirnstammerkrankungen. Monatsschr Psychiatr Neurol. 1919. ↩︎
Karnath HO. Nature of neglect in corticobasal degeneration. Brain. 2001. ↩︎
Hillis AE, Karnath HO, Frisina R, et al. Anatomical correlates of neglect in corticobasal syndrome. Cortex. 2005. ↩︎