Last week we discussed a paper about a group of university researchers who created a biomarker for post traumatic stress disorder (PTSD) using magnetoencephalography (MEG) and fancy statistics. There is an active body of research looking into important questions concerning PTSD. Today, I wanted to look at another imaging modality and discuss its ability to observe changes in brain activity. Although this paper does not explore creating a biomarker for PTSD, it does look at differences between patients with PTSD and people that do not have the condition using SPECT imaging.
The use of SPECT brain imaging in studying PTSD can be effective and helpful. This is the first SPECT study to examine differences in a brain region called the thalamus in both an experimental and a control group4. All subjects were involved in the same traumatic event (in this case it was a subway fire in Korea). Images of subjects’ brains were compared to those of an age matched control group. What the studied showed was a decrease in blood flow in the thalamus (a region involved in sensory relay, and regulation of consciousness, sleep and alertness) and an increase in the blood flow in a region of the parietal lobe (the association area that integrates sensory information). The changes seen in the thalamus were similar to changes seen in previous reports which used functional magnetic resonance imaging (fMRI). Previous research has shown that SPECT imaging has been good at detecting changes cerebral blood flow in certain brain regions when patients are at rest and when they are in active recall of the event 1-3. This paper examined subjects in a resting state (this is important when examining differences among studies because tasks that subjects do have a direct result on activity levels in brain regions. This may seem obvious, but these details need to be clear for comparisons across studies). What I find interesting is people with PTSD usually have a heightened startle response, which would make me think that you would see increased activity in the thalamus because it is involved in alertness. However, clearly the condition is more complicated than that. One last thing, this is one of the only papers that I have seen that puts limitations of the paper right up front for you. This strategy can be good and bad.
Since they looked at regions that are involved in sensory integration and processing, they speculated that symptoms of PTSD, could be treated with some type of sensory treatment regimen and thus may help with decreasing symptoms of the condition.
One difference between MEG and SPECT is MEG is used more in research, while SPECT is used in research and in the clinic. Therefore, SPECT has the ability to diagnose and aid clinicians in the treatment of the condition. Regardless of the limitations of the study, SPECT can be used in clinical situations for patients who may have symptoms, such as depression, irritability and anxiety that may be the result of a traumatic event and has led to PTSD.
1. Lindauer RJ, BooijJ, Habraken JB et al. Cerebral blood flow changes during script-driven imagery in police officers with post traumatic stress disorder. Biol Psychiatry; 2004; 56: 853–861.
2. Sachinvala N, Kling A, Suffin S, Lake R, Cohen M. Increased regional cerebral perfusion by 99mTc hexamethylpropyleneamineoxime single photon emission computed tomography in post-traumatic stress disorder. MilMed 2000; 165:473–479.
3. Chung YA, Kim SH, Chung SK et al. Alterations in cerebral perfusion in post traumatic stress disorder patients without re-exposure to accident-related stimuli. Clin Neurophysiol: 2006; 117:637–642.
4. Kim SJ, Lyoo IK, Lee YS, Kim J, Sim ME, Bae SJ, Kim HJ, Lee JY, Jeong DU. Decreased cerebral blood flow of thalamus in PTSD patients as a strategy to reduce re-experience symptoms. Acta Psychiatr Scand. 2007 Aug; 116(2):145-53.