Constructional dysfunction (also termed constructional apraxia) is a significant cognitive deficit in corticobasal syndrome (CBS), characterized by the inability to copy, draw, or construct simple geometric figures or patterns. This deficit emerges from the parietal lobe dysfunction that is hallmark of CBS and serves as an important diagnostic feature distinguishing CBS from other parkinsonian syndromes like Parkinson's disease.
Constructional dysfunction occurs in approximately 40-60% of CBS patients, making it one of the more common cognitive deficits. The prevalence is significantly higher than in progressive supranuclear palsy (PSP), where constructional abilities are relatively preserved until later disease stages.
| Region | Function | CBS Involvement |
|---|---|---|
| Posterior Parietal Cortex (Brodmann areas 7, 5) | Spatial processing, coordinate transformation | Primary — asymmetric atrophy common |
| Superior Parietal Lobule | Visual-motor integration | Primary — critical for construction |
| Inferior Parietal Lobule ( areas 39, 40) | Visuospatial analysis, attention | Primary — often affected |
| Premotor Cortex (BA 6) | Motor planning for drawing | Secondary — contributes to output |
| Dorsolateral Prefrontal Cortex | Executive control | Secondary — may be involved |
| Occipital Visual Areas | Visual processing | Secondary — feedforward input |
The characteristic asymmetric onset of CBS often results in constructional deficits that are worse on the side opposite to the more affected cerebral hemisphere. This lateralization is diagnostically valuable:
Patients with constructional dysfunction demonstrate deficits on:
Copying figures
Drawing from memory
Block construction
Matching tasks
| Grade | Performance |
|---|---|
| Mild | Copies simple figures accurately; difficulty with complex figures |
| Moderate | Copies simple figures with errors; unable to assemble blocks |
| Severe | Cannot copy basic shapes; drawings fragmented or disorganized |
| Condition | Constructional Function | Key Distinction |
|---|---|---|
| CBS | Impaired early (40-60%) | Asymmetric, early onset |
| PSP | Intact until late | Preserved longer than CBS |
| PD | Generally intact | Relatively spared |
| Posterior Cortical Atrophy (PCA) | Severely impaired | More severe than CBS |
| AD | Impaired in moderate-severe disease | Later onset in AD |
| FTD | Variable | Depends on subtype |
Rey-Osterreith Complex Figure (ROCFT)
Block Design (WAIS-IV, WISC)
Clock Drawing Test
Compensatory Strategies
Errorless Learning
Environmental Adaptations