Researchers map brain atrophy in progressive supranuclear palsy

NeuRA researchers have completed the first systematic study of brain atrophy in people with progressive supranuclear palsy.

Progressive supranuclear palsy, or PSP, is a degenerative brain disease that causes difficulty in movement and cognition, and is easily misdiagnosed as Parkinson’s disease. The disease pathology is characterised by a build up of the tau protein in the brain and atrophy, or wasting away, of brain tissue.

“This is the most comprehensive atrophy study for PSP that’s been done looking at different functional areas of the brain,” says Dr Emma Schofield, lead author of the study.

“It’s significant because a diagnosis of PSP is made, in part, using MRI, which indicates the location and extent of atrophy in the brain,” she says. “By understanding the patterns of atrophy in the brain in PSP, we can improve our diagnosis of this disease.”

PSP affects people over the age of 60 and, at present, there is no treatment. The disease is progressive, and life expectancy is six to seven years after the first appearance of symptoms.

There are two subtypes of PSP, known as Richardson’s syndrome or classic PSP, and parkinsonian PSP, which is more similar to Parkinson’s disease.

Dr Emma Schofield and colleagues looked at the brains of 24 people with PSP and 22 healthy controls, from the brain donor program at the Sydney Brain Bank. The team found that considerable atrophy in the classic form of PSP occurs in the cortex, or outer layer of the brain. This differs from Parkinson’s disease, where the midbrain, or inner parts of the brain, are affected.

“PSP has traditionally been thought to be a disease of the subcortex, affecting the more primitive parts of the brain,” says Dr Schofield. “But in fact, we found that in classic PSP, the frontal and parietal cortices are equally affected.”

These areas of the brain are responsible for cognition, executive function, the control of attention and eye movements, and our ability to integrate sensory-motor information.

“The location of this atrophy explains the symptoms of cortical dysfunction seen in classic PSP, as opposed to parkinsonian-PSP and Parkinson’s disease, where movement is more heavily affected,” she says.

It is not known what causes the brain atrophy in PSP; one theory suggests the cells are dying due to the presence of the tau protein.

However, Dr Schofield also found that the degree and location of brain atrophy in PSP does not necessarily correspond with the location of tau protein as previously thought.

“It is puzzling why the wasting doesn’t closely relate to the formation of tau pathology. This research indicates that there are a whole lot of other processes that take place in PSP in between the formation of tau and the loss of cells.”

“This means that we need to look a lot more closely at what part of the degenerative process is causing the symptoms of the disease” she says.

The study was published in the journal Movement Disorders.