Image copyright Marc Phares/SCIENCE PHOTO LIBRARY

Scientists have proposed a new idea for detecting brain conditions including Alzheimer's - a skin test.

Their work, which is at an early stage, found the same abnormal proteins that accumulate in the brain in such disorders can also be found in skin.

Early diagnosis is key to preventing the loss of brain tissue in dementia, which can go undetected for years.

But experts said even more advanced tests, including ones of spinal fluid, were still not ready for use.

Brain biomarker

Investigators have been hunting for suitable biomarkers in the body - molecules in blood or exhaled breath, for example, that can be measured to accurately and reliably signal if a disease or disorder is present.

Dr Ildefonso Rodriguez-Leyva and colleagues from the University of San Luis Potosi, Mexico, believe skin is a good candidate for uncovering hidden brain disorders.

Skin has the same origin as brain tissue in the developing embryo and might, therefore, be a good window to what's going on in the mind in later life - at least at a molecular level - they reasoned.

Post-mortem studies of people with Parkinson's also reveal that the same protein deposits which occur in the brain with this condition also accumulate in the skin.

To test if the same was true in life as after death, the researchers recruited 65 volunteers - 12 who were healthy controls and the remaining 53 who had either Parkinson's disease, Alzheimer's or another type of dementia.

They took a small skin biopsy from behind the ear of each volunteer to test in their laboratory for any telltale signs of disease.

Image copyright SPL Image caption Skin biopsies from behind the ear showed telltale protein deposits

Specifically, they looked for the presence of two proteins - tau and alpha-synuclein.

The 20 people with Alzheimer's and the 16 with Parkinson's had raised levels of both these proteins in their skin compared to the healthy controls and the patients with other types of dementia.

The people with Parkinson's also had higher levels of alpha-synuclein protein.

Dr Rodriguez-Leyva, who will soon present his findings to the annual meeting of the American Academy of Neurology, said: "More research is needed to confirm these results, but the findings are exciting because we could potentially begin to use skin biopsies from living patients to study and learn more about these diseases.

"This new test offers a potential biomarker that may allow doctors to identify and diagnose these diseases earlier on." It could also guide research into new treatments, he said.

Dr Arthur Roach, Parkinson's UK Director of Research and Development, said: "This work points to a possible diagnostic test that would be minimally invasive and could provide earlier, more accurate diagnosis.

"There is still a need for more innovation in this area - at the moment there's no way to definitively diagnose Parkinson's."

Dr Simon Ridley of Alzheimer's Research UK said it was too early to say if a skin test would become available.

He said research into biomarkers in cerebrospinal fluid - the fluid that surrounds the brain and spinal cord - was at a more advanced stage, but that even these methods were not yet close to becoming a routine test.

Progressive brain diseases

Image copyright SPL Image caption Loss of tissue in a demented brain compared with a healthy one