MAPrc ear canal invention a new tool in identifying depression

by Anne Crawford

Bipolar Disorder and Major Depressive Disorder (or MDD) can appear similar in patients but distinguishing them is vital for clinicians to give the right and most efficacious treatment.

Monash Alfred Psychiatry Research Centre (MAPrc) researchers have developed a novel way of doing this – by recording the electrical activity from the outer ear canal. Their findings were published recently in a paper in The World Journal of Biological Psychiatry.

Depression, a deep sadness, is characterised by a pervading low mood. People with Bipolar experience the opposite ends or poles of emotion – the lows (depression) and the highs (mania). However, they might have a large number of depressive episodes before a hypomanic one, meaning it could take months or years to be correctly diagnosed.

Studies suggest that up to 40% of bipolar disorder patients are initially misdiagnosed with major depressive disorder, the paper said.

“The difficulty is when you’re diagnosing the depression you generally want to give the patient some medication (or treatment),” Professor Brian Lithgow said. “But if you muck up the medication for bipolar patients thinking they have major depression you can actually push them into a manic phase that can have bad results for the patient.”

This graph shows the separation of 27 control,
43 bipolar and 39 major depressed patients.

Someone who’s in a manic phase could believe, for example, that God has told them to do certain things, become suicidal or believe that they can’t die. “So it’s really important to be able to identify them to give the best medication or treatment regime,” Professor Lithgow said.

The researchers used a process called electrovestibulography (EVestG), in which an electrode is inserted in the ear canal to measure the nerve signal patterns of the vestibular nerve. The vestibular nerve detects orientation of the head with respect to balance, and also acceleration in the body. It also has intricate links to the emotional and behavioural parts of the brain such as the limbic system.

EVestG measures this nerve’s firings. In the study, graphs generated by these firings showed differences in the patterns of signals between recordings taken from depressive patients and bipolar patients in a depressive phase.

“The firing patterns allow us to determine which of the two depressions they have,” Professor Lithgow said.

The results showed better than 80% accuracy could be achieved for identifying MDD from bipolar disorder subjects when excluding controls, the paper said.

A double-blind study with a larger sample size was now required, it said.

Said senior author Professor Paul Fitzgerald, “We urgently need mechanisms to improve the diagnosis and management of mental health conditions and hopefully this research can contribute to the development of an effective and novel clinical tool.”

EVestG was invented in 2006 by Professor Lithgow and co-investigated by MAPrc Director Professor Jayashri Kulkarni AM and Professor Paul Fitzgerald with the aim of providing an objective diagnosis of mental illness, akin to an ECG for the mind.

Professors Jayashri Kulkarni AM and Brian Lithgow accepting
the ABC’s New Inventors program ‘Invention of the Year'
award in 2010

 It has been used since by MAPrc researchers in studies defining vertiginous disorders, post-concussion syndrome, Parkinson’s disease, and dementia including Alzheimer’s disease.

The technology was selected as a Telstra Innovation Challenge finalist in 2009 and was awarded ‘Invention of the Year’ in 2010 by the ABC’s New Inventors program. The “EVestigator” team from the MAPrc and Neural Diagnostics Pty Ltd (NDPL), led by Professors Kulkarni and Lithgow, was shortlisted for the 2015 Eureka Prize for Excellence in Interdisciplinary Scientific Research.

EVestG, which also consists of a recording chamber and hydraulic chair, has been patented but not commercialised. “At the moment we’re trying to miniaturise it, incorporating it all into a set of headphones,” Professor Lithgow said.

Professor Lithgow has a joint appointment at MAPrc, the Central Clinical School and the Alfred Hospital and the University of Manitoba, Winnipeg, Canada.

Lithgow BJ, Moussavi Z, Fitzgerald PB. Quantitative separation of the depressive phase of bipolar disorder and major depressive disorder using electrovestibulography. World J Biol Psychiatry. 2019 Mar 26:1-14. doi: 10.1080/15622975.2019.1599143. [Epub ahead of print]

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