Objective diagnosis is in some
ways the holy grail of medicine. It has been maddeningly elusive
in psychiatry. Now comes a paper in which the authors suggest
that they may have found this treasure.The paper details a method of using magnetoencephalography to assess human brain function. They claim that, in a select population, it can correctly identify patients with PTSD with 90% accuracy.
The synchronous neural interactions test as a functional neuromarker for post-traumatic stress disorder (PTSD): a robust classification method based on the bootstrap
2010 J. Neural Eng. 7 016011
Abstract. Traumatic experiences can produce post-traumatic stress disorder (PTSD) which is a debilitating condition and for which no biomarker currently exists (Institute of Medicine (US) 2006 Posttraumatic Stress Disorder: Diagnosis and Assessment (Washington, DC: National Academies)). Here we show that the synchronous neural interactions (SNI) test which assesses the functional interactions among neural populations derived from magnetoencephalographic (MEG) recordings (Georgopoulos A P et al 2007 J. Neural Eng. 4 349-55) can successfully differentiate PTSD patients from healthy control subjects. Externally cross-validated, bootstrap-based analyses yielded >90% overall accuracy of classification. In addition, all but one of 18 patients who were not receiving medications for their disease were correctly classified. Altogether, these findings document robust differences in brain function between the PTSD and control groups that can be used for differential diagnosis and which possess the potential for assessing and monitoring disease progression and effects of therapy.
The synchronous neural interactions test is a test that is done by having persons perform a simple task, while the magnetic signals from their brain are being measured. The process is called magnetoencephalography. The resulting record is called a magnetoencephalogram (MEG). It is similar to an electroencephalogram (EEG). The difference is that the EEG measures small electric currents. The MEG measures magnetic impulses. These impulses are only slightly affected by the intervening tissue (skull, skin, etc). Therefore, it is possible to get readings that are more precise. The downside is that it requires a more elaborate device, and a special, magnetically-shielded, room. Very few of these devices exist.
Patients for the study were recruited from a population of military
veterans. A total of 74 patients were studied. The patient
population consisted mostly of persons with PTSD related to
warfighting. Some had PTSD linked to abuse during
childhood. Some had non-combat trauma during adulthood. The
majority were Vietnam veterans. Fifty-six were receiving
medication for PTSD.
Many potential subjects were excluded:
The outcome was more robust than I would have expected:
Of course, it remains to be seen if this can be replicated, and if it can be extended to a more diverse population. There have been many previous attempts to find clinically-useful biomarkers for psychiatric conditions. So far, none has emerge as being generally applicable.
One of the problems is that attempts to extend the population under study tend to lead to loss of diagnostic precision. Notice the list of exclusion criteria, applied to potential patients. That list would also exclude a large proportion of patients presenting for assessment in a non-research-oriented clinic. The exclusion of persons with substance abuse is particularly troublesome. Not only does it narrow the population considerably, but it means that the patients studied may not be typical of all patients with PTSD. (PTSD increases the risk of developing a substance abuse problem by a factor of 4.5.)
Another problem is that most of the patients had PTSD related to wartime trauma. Although the population did include some civilian trauma, it is not clear at this point how well this technique would work in a civilian population.
A nice aspect of this study, and its outcome, is that it does not appear to matter whether or not the patients were taking medication. However, it reamins to be seen if this will be true generally.
If this works well, can be replicated, and can be extended to a general population, it could be helpful in clinical use. As it happens, there is already a great deal of controversy over the diagnosis, particujlarly with regard to disability benefits. Our very own David Dobbs (Neuron Culture) has been waving a caution flag for a while. Mike Dunford (The Questionable Authority) has a roundup of reactions to that issue, including his own take on it.
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Citation:
Georgopoulos, A., Tan, H., Lewis, S., Leuthold, A., Winskowski, A., Lynch, J., & Engdahl, B. (2010). The synchronous neural interactions test as a functional neuromarker for post-traumatic stress disorder (PTSD): a robust classification method based on the bootstrap Journal of Neural Engineering, 7 (1) DOI: 10.1088/1741-2560/7/1/016011
Many potential subjects were excluded:
To minimize subject burden, we did not contact veterans with indicators of instability within the last 6 months (e.g. inpatient medical or mental health treatment, significant changes in health or medications, etc) or those with psychotic disorders based on medical record review. We also excluded veterans with active substance use disorders, serious chronic pain and other CNS disorders (e.g. Parkinson's disease, dementia, cerebral vascular accidents, etc).
The outcome was more robust than I would have expected:
Finally, of 18 non-medicated PTSD patients, only one was misclassified and 17/18 = 94.4% were correctly classified. Similarly, of the 56 medicated patients, only one was misclassified and 55/56 = 98.2% were correctly classified. These two classification proportions between the non-medicated and medicated PTSD patients did not differ statistically significantly.
Of course, it remains to be seen if this can be replicated, and if it can be extended to a more diverse population. There have been many previous attempts to find clinically-useful biomarkers for psychiatric conditions. So far, none has emerge as being generally applicable.
One of the problems is that attempts to extend the population under study tend to lead to loss of diagnostic precision. Notice the list of exclusion criteria, applied to potential patients. That list would also exclude a large proportion of patients presenting for assessment in a non-research-oriented clinic. The exclusion of persons with substance abuse is particularly troublesome. Not only does it narrow the population considerably, but it means that the patients studied may not be typical of all patients with PTSD. (PTSD increases the risk of developing a substance abuse problem by a factor of 4.5.)
Another problem is that most of the patients had PTSD related to wartime trauma. Although the population did include some civilian trauma, it is not clear at this point how well this technique would work in a civilian population.
A nice aspect of this study, and its outcome, is that it does not appear to matter whether or not the patients were taking medication. However, it reamins to be seen if this will be true generally.
If this works well, can be replicated, and can be extended to a general population, it could be helpful in clinical use. As it happens, there is already a great deal of controversy over the diagnosis, particujlarly with regard to disability benefits. Our very own David Dobbs (Neuron Culture) has been waving a caution flag for a while. Mike Dunford (The Questionable Authority) has a roundup of reactions to that issue, including his own take on it.
___________
Citation:
Georgopoulos, A., Tan, H., Lewis, S., Leuthold, A., Winskowski, A., Lynch, J., & Engdahl, B. (2010). The synchronous neural interactions test as a functional neuromarker for post-traumatic stress disorder (PTSD): a robust classification method based on the bootstrap Journal of Neural Engineering, 7 (1) DOI: 10.1088/1741-2560/7/1/016011
Comments
What an exciting post! There are a number of diagnostic problems that truly do exist but biomarkers are not available. Therefore, their diagnosis and treatment is downplayed in allopathic medicine and those in integrative medicine see so many of the sufferers.
Chronic Fatigue Immunodeficiency
Fibromyalgia
Chemical Hypersensitivity
and other conditions with protean symptoms have many common features with PTSD. IMHO, they will all be found to have diagnostic and therapeutic similarities. I hope that this powerful tool can step in and prove those with these conditions won't have to fight diagnostic inertia for much longer.
Posted by: Pietr | February 8, 2010 10:29 PM
One thing I don't like in this paper is that they don't give any argument or explanation of the mechanism behind the diagnosis. Shine a light into the eyes of PTSD sufferers, then diagnose? What an auditory stimuli? Where's the reasoning why. It just seems very naive to diagnose a complicated neurological/psyhological disorder by letting a patient sit and stare into a light and comparing the reaction to a control subject. Maybe I'm just missing something here, as a small-time EEG researcher.
Posted by: JMG | February 10, 2010 2:49 PM
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PTSD: Hard to find (diagnostically), easy to fix (therapeutically). Or vice versa. Maybe perhaps.
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Full text HERE:
Psychedelic Healing? - Hallucinogenic drugs, which blew minds in the 1960s, soon may be used to treat mental ailments, By David Jay Brown, Scientific American Mind, December 07
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[Original web version behind paywall at http://www.sciam.com/article.cfm?id=psychedelic-healing&sc=WR_20080108 ]
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Posted by: Meremark | March 18, 2010 2:59 AM