Progressive supranuclear palsy - Causes of progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is caused by damage to brain cells in the parts of the brain that help control movement, balance, vision and speech.

Tau protein

Some of the brain cells are damaged by a protein called tau. Tau occurs naturally in the brain, but people with PSP have much higher levels. 

Tau is usually broken down in the brain. However, in PSP the tau changes slightly, allowing clumps to build up and damage cells. 

PSP has similar symptoms to another neurodegenerative condition called corticobasal degeneration (CBD), although the pattern of brain damage is slightly different. It may be that both PSP and CBD are related syndromes that are the result of the same underlying cause or causes.

It's not known what leads to the overproduction of tau protein and the resulting death of brain cells. Recent research has indicated that genetic factors can make someone more likely to develop PSP, but cases of PSP are nearly always a one-off in a family. The risk to other members of the family, including children or siblings of someone with PSP, is very low. 

It's important to note that there's no evidence to suggest that PSP can be passed from a parent to their child, and most experts think that it's unlikely that PSP is an inherited condition.

Environmental factors

Further research is underway to identify other factors may trigger PSP. Suggested environmental triggers include:

• an unidentified virus or other type of infection, which may slowly infect the brain over the course of many years
• an unidentified neurotoxin (a poison that damages brain and nerve cells) that may be present in the environment