Australian researchers have shown how two diseases which present in similar ways are in fact very different.

A team at the University of Melbourne says its finding will help break down some challenges in diagnosing the different conditions.

Progressive Supranuclear Palsy (PSP) and Parkinson’s Disease (PD) have overlapping symptoms, and can be very difficult to distinguish from each other.

But a brand new paper (the first ever produced on the topic) now suggests that people with PSP experience more severe and extensive cognitive impairments than those with PD, early on at least.

The study, published in the Journal of Neuropsychology, indicates that patients with PSP experience more severe and extensive impairments in higher order functions such as planning, abstract thinking, memory retrieval than those with PD.

Lead researcher Dr Young-Eun Claire Lee said the two conditions are so similar that in some cases, patients with PSP often go undiagnosed for the main part of their illness.

“PD and PSP are the two of the most common forms of neurodegenerative diseases resulting in loss of balance and deterioration in mobility,” said Dr Lee.

“Telling these differences apart can be challenging because most patients with PSP do not develop distinctive symptoms such as paralysis or weakness of the eye muscles and episodes of frequent falling until later stages,” she said.

While the study sample was small, the results indicate that cognitive profiles may aid differential diagnosis in earlier stages.

There is currently no treatment for PSP.