DTI is a specialised imaging technique that uses MRI technology to investigate the movement of water within tissues of interest. By applying a magnetic field, the movement (“diffusivity”) of water molecules can be visualised in vivo. The diffusion of water is influenced by the cellular structure of the surrounding tissues, and measures such as fractional anisotropy (FA) were derived as an approximate measurement for the freedom of movement. In areas of high structural coherence such as white matter, FA is highest, indicating that water is moving in relatively fixed directions. It is lower in grey matter, and close to zero in cerebrospinal fluid, indicating that water is moving freely. Consequently, changes in FA values are interpreted to be representing alterations in the structural integrity of the regional white matter. Alterations in white matter have been found in schizophrenia and bipolar disorder, and has been investigated in PTSD.

What is the evidence for changes in white matter in people with PTSD?

Moderate to high quality evidence found both region of interest and whole brain meta-analyses showed that patients with PTSD have significantly higher FA in the inferior fronto-occipital fasciculus and lower FA in the genu of the corpus callosum. Whole brain meta-analyses also identified higher FA in the left inferior temporal gyrus and lower FA in the anterior cingulum and left corticospinal tract.

August 2021

Image: ©Michael Braham – shutterstock.com

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The technology of structural MRI is based on the magnetisation properties of cellular protons. The application of a strong magnetic field causes the protons within cells to shift direction, which will return to their original position over time (“precession”). The rate of precession differs across tissue types (such as grey matter and white matter in the brain), which can be interpreted by specialised programs to represent a 3D image. Many mental disorders have shown brain structural changes investigated with MRI, including schizophrenia and bipolar disorder.

What is the evidence for changes in brain structure in PTSD?

Moderate quality evidence found small to medium-sized reductions in total brain volume, intracranial volume, left insula, right insula, total insula, superior frontal gyrus, left middle temporal gyrus, inferior temporal gyrus, left anterior cingulate, total anterior cingulate, rostral anterior cingulate, lateral orbitofrontal cortex total amygdala, left hippocampus, right hippocampus, and total hippocampus in people with PTSD compared to controls.

Moderate to low quality evidence found medium-sized effects of reduced hippocampus volume and large effects of reduced amygdala volume in people with PTSD who were exposed to childhood abuse compared to controls.

Moderate quality evidence found small to medium-sized reductions in grey matter, cerebral volume, temporal lobe, hippocampus, and vermis in children with PTSD compared to controls. There were also non-significant, small reductions in the amygdala.

Moderate to low quality evidence found increased PTSD symptom severity was significantly associated with decreased volume of the left, but not the right, hippocampus.

Compared to people with major depressive disorder, people with PTSD had reduced total brain volume and increased thalamus volume. Both PTSD and depression patients had significantly smaller hippocampal volume compared with controls, with no difference between the patient groups in this brain region.

August 2021

Image: ©Kondor83 – Fotolia – stock.adobe.com

The post MRI appeared first on NeuRA Library.

Telomeres are protective caps on the ends of chromosomes. They are linked to aging as they shorten with each cell division, and when they reach a critical length, the cell stops dividing or dies. Chronic stress has been associated with reduced telomere length, resulting in the recognition of an association between adverse social and environmental influences and accelerated aging. Telomere length has been found to be shorter in people with schizophrenia, but not in people with bipolar disorder. It has recently been investigated in people with PTSD.

What is the evidence for telomere length in people with PTSD?

Moderate to high quality evidence found a small effect of shorter telomere length in people with PTSD compared to controls.

August 2021

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