PARKINSON’S DISEASE is a progressive neurological disorder caused by the deaths of neurons in parts of the brain called the substantia nigra. Symptoms include loss of motor control, mood disturbance, ruined sleep and altered sense of smell. It is incurable. Early medical intervention can, however, relieve these symptoms and prolong survival. That makes prompt diagnosis desirable.
Unfortunately, the initial signs of Parkinson’s vary from person to person and there is no specific test at this early stage which can reliably distinguish it from other brain illnesses. It therefore often goes undetected until clear and characteristic manifestations, such as tremors and slowed body movement, appear. But that may soon change. A study published in ACS Omega, by Chen Xing and Liu Jun at Zhejiang University, in China, describes an invention which may be able to detect Parkinson’s before the onset of tremulousness. The device in question is an artificially intelligent electronic nose.
A whiff of trouble
The quest the two researchers embarked on to build this nose began in 2019. That was when they heard reports of Joy Milne, a retired nurse living in Scotland, who could detect people with Parkinson’s from a distinctive odour they emitted—distinctive to her, at least, though for reasons still obscure, undetectable by others.
Mrs Milne first noticed this odour when her husband developed the illness. She made the general connection later, when she smelled it at sufferers’ support groups attended by her spouse. Tests using clothes worn by patients confirmed her ability. She even noted one seemingly healthy individual as having the disease months before other symptoms developed.
Carting Mrs Milne around the world to sniff patients who may have Parkinson’s is, however, not a practical option, so researchers working with her looked for the odour’s source, with a view to detecting it in some other way. They found it in sebum, an oily secretion produced by the skin. The sebum of those with Parkinson’s, they discovered, has unusually high concentrations of certain volatile organic compounds, including dodecane, acetone and ethyl acetate. When these are acted on by yeast cells which live naturally on the skin, the result is the mysterious odour.
This Parkinson’s-specific list can be detected using a laboratory technique called gas chromatography-mass spectrometry (GCMS), which is promising—for GCMS machines are a bit more deployable than Mrs Milne is. Unfortunately, they are still too complex and expensive to be used routinely in clinics. However, Dr Chen and Dr Liu, who are both biomedical engineers, reckoned they could come up with a cheaper and more portable alternative.
The upshot is a machine not much bigger than a toaster. It turns a sample of sebum into a vapour that is then probed with sound waves. Different molecular mixtures have different effects on the waves, and, with a bit of training, a computer loaded with an appropriate piece of artificial intelligence can learn to recognise the pattern associated with sebum from Parkinson’s patients.
The researchers tested their system on samples from 43 people with Parkinson’s disease and 44 who were healthy. They found it could correctly identify a Parkinson’s patient as having the disease about 70% of the time and a healthy control as being clear of it about 80%. That is not yet as good as Mrs Milne’s nose, which has a history of correctly identifying the presence of Parkinson’s all the time. But it is a start. If its reliability can be improved, the compactness and potential cheapness of the system Dr Chen and Dr Liu have come up with may eventually prove a boon for the early diagnosis of the illness. ■
This article appeared in the Science & technology section of the print edition under the headline “The nose knows”