Correlation of Serum Neurosteroid Levels with Cortical Thickness in People with Mild Traumatic Brain Injury and Post-Traumatic Stress Disorder

Mild traumatic brain injury (mTBI) and post-traumatic stress disorder are prevalent comorbidities observed in soldiers. PTSD and mTBI have a high rate of prevalence as comorbidities particularly in soldiers. Furthermore, mTBI has been shown to increase the risk of occurrence of PTSD.

Correlation of Serum Neurosteroid Levels with Cortical Thickness in People with Mild Traumatic Brain Injury and Post-Traumatic Stress Disorder

Studies conducted with advanced brain imaging techniques have shown that both diseases cause changes in the brain structure. A lower volume of gray matter (GM) in the anterior cingulate cortex (ACC) and prefrontal cortex and hippocampus, and a lower cortical thickness have been reported in the post-traumatic stress disorder. Moreover, there are evidences setting forth that cortical thickness is associated with the severity of symptoms in Post-traumatic stress disorder. In addition to prevalent changes in gray matter in mild traumatic brain injury, it has also been observed that the global brain volume and the gray matter volume in the precuneus region reduce within the first year of the injury. Moreover, it has been also reported there is a reduction in the gray matter volumes of the subcortical structures, including thalamus, hippocampus, amygdala and putamen.

In addition to the changes in the brain structure observed in post-traumatic stress disorder and mild traumatic brain injury, the role of the changes in endocrine is emphasized in both disorders.

Chronic stress is known to cause irregularities on the axis of hypothalamus-hypophysis-adrenal (HPA) that includes the changing neurosteroid-glucocorticoid levels in the prefrontal cortex and the increasing levels of catecholamine.

The clinical results of people with PTSD have been associated with the decreasing levels of serum neurosteroid. Furthermore, a reduced cortical thickness has been associated both with PTSD and mTBI.

In a study, the correlation between the cortical thickness, ALLO (allopregnanolone) and PREGN (pregnenolone) serum levels was researched in individuals with a background of PTSD + mTBI, individuals with a background of only mTBI, and healthy controls. There were three main data regarding the PTSD + mTBI group: The first one includes the reduction of the cortical thickness in various brain regions, including temporal and frontal cortex regions, as observed in the comparison of the individuals with PTSD and mTBI both to the individuals with mTBI and the controls. Secondly, the thinner the cortex is in these brain regions, the higher the PTSD symptom severity gets. Thirdly, the cortical thickness in these regions of the brain is positively correlated with the serum ALLO and PREGN levels. When considered together, these findings shown that there is a correlation between the cortical thickness and PTSD symptoms in the key regions related to neurosteroids, which are believed to have protective effects, and frequently to anxiety disorders.

REFERENCES:
– Kinzel, P., Marx, C. E., Sollmann, N., Hartl, E., Guenette, J. P., Kaufmann, D., … Koerte, I. K. (2020). Serum Neurosteroid Levels Are Associated With Cortical Thickness in Individuals Diagnosed With Posttraumatic Stress Disorder and History of Mild Traumatic Brain Injury. Clinical EEG and Neuroscience.