Progressive Supranuclear Palsy - Pathophysiology

Pathophysiology

The affected brain cells are both neurons and glial cells. The neurons display neurofibrillary tangles, which are clumps of tau protein, a normal part of a brain cell's internal structural skeleton. These tangles are often different from those seen in Alzheimer's disease, but may be structurally similar when they occur in the cerebral cortex. Their chemical composition is usually different, however, and is similar to that of tangles seen in corticobasal degeneration. Lewy bodies are seen in some cases, but it is not clear whether this is a variant or an independent co-existing process.

The principal areas of the brain affected are:

• the basal ganglia, particularly the subthalamic nucleus, substantia nigra and globus pallidus;
• the brainstem, particularly the portion of the midbrain where "supranuclear" eye movement resides;
• the cerebral cortex, particularly that of the frontal lobes;
• the dentate nucleus of the cerebellum;
• and the spinal cord, particularly the area where some control of the bladder and bowel resides.

Some consider PSP, corticobasal degeneration, and frontotemporal dementia to be variations of the same disease. Others consider them separate diseases. PSP has been shown occasionally to co-exist with Pick's disease.