In hopes of better understanding the growing issue of post-traumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI) among soldiers, the Canadian Armed Forces approached researchers at The Hospital for Sick Children (SickKids). Known for their expertise in a type of neuroimaging called MEG, magnetoencephalography, SickKids researchers used MEG to examine brain responses to a variety of cognitive tasks in soldiers with and without PTSD and civilians with and without mTBI.
“While the two disorders can be confused because of similar behavioural symptoms, the data show that they are very distinct,” says Dr. Margot Taylor, co-investigator of the research and Director of Functional Neuroimaging and Senior Scientist at SickKids. “This research could lead to faster diagnosis based on objective measures rather than having a soldier self-identify, which according to Canadian Forces Health Services is an ongoing challenge.”
Currently PTSD and mTBI are diagnosed clinically based on emotional and psychological symptoms. The symptoms of these two conditions show considerable overlap, and particularly in the military setting, are often both present and difficult to distinguish.
While the use of MEG to study PTSD is relatively novel, clinicians at SickKids have been using MEG as a diagnostic tool for children with epilepsy for many years. In fact, the SickKids Epilepsy Program is a world leader in developing and implementing use of MEG as a non-invasive diagnostic tool to select children for epilepsy surgery. “MEG has excellent resolution for locating areas in the brain that generate seizures. This is particularly important for children with intractable focal epilepsy as it provides crucial pre-surgical information that we previously would not have had without implanting electrodes on the patient’s brain,” says Dr. Elizabeth Pang, who is Neurophysiologist and Associate Scientist at SickKids, and co-investigator of the PTSD research.
MEG is the only brain imaging technique that provides millisecond timing resolution with millimeter spatial resolution, meaning it is the most precise tool available to determine when events take place in the brain and in which part of the brain.
Drs. Pang and Taylor also use MEG to investigate cognitive functions such as memory, emotional processing, mental flexibility, inhibition and language in children with Autism Spectrum Disorder (ASD) and children born very preterm (<32 weeks gestational age). The tasks used in this recent PTSD/mTBI research were based on these other clinical MEG studies and address the cognitive difficulties commonly associated with PTSD and mTBI which included tests of memory, inhibition, attention, mental flexibility and emotional processing.
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The team studied not only soldiers with PTSD and civilians with mTBI, but also had a control group of soldiers with similar military experience who did not have PTSD or mTBI. The difference in brain activity between the clinical group and their respective control group was remarkable. For example, while all groups demonstrated significant brain responses to the cognitive tests, the soldiers without PTSD could return to a resting state while those with PTSD remained highly activated even in a rested state.
“The ultimate goal of providing objective diagnostic testing for PTSD and mTBI is to not only better understand the conditions and make fast, accurate diagnoses, but also to be able to test the individual to determine if he or she can safely return to service,” says Taylor.
Taylor adds that this work also helps advance our understanding of PTSD and traumatic brain injury in children and the general population.
The PTSD/mTBI research was conducted in partnership with Defense Research and Development Canada and by Canadian Forces Health Services. The research of Drs. Pang and Taylor with children with autism or very preterm-born children is funded by the Canadian Institutes of Health Research.