A brain imaging study led by Duke University has found that adults with post-traumatic stress disorder (PTSD) have smaller cerebellums. The cerebellums of people with PTSD are about 2 percent smaller than those of unaffected adults, particularly in areas that affect mood and memory. The cerebellum, a part of the human brain known for helping coordinate movement and balance, can affect mood and memory, which can be affected by PTSD. What remains unclear is whether a smaller cerebellum causes PTSD or if PTSD shrinks the cerebellar region.
The cerebellum (shown with a pointer) contains half of the brain's neurons, which are packed tightly together. New research shows that post-traumatic stress disorder is associated with a smaller cerebellum, providing new insights into the neurological basis of the disorder and potential treatments. Image source: Dan Vahaba, Duke University
"The differences were primarily in the posterior lobes, where a lot of cognitive functions in the cerebellum appear to be concentrated, while the vermis is associated with a lot of emotional processing," said Dr. Ashley Huggins, the report's lead author. Huggins, now an assistant professor of psychology at the University of Arizona, hopes the results will encourage others to consider the cerebellum as an important medical target for patients with PTSD.
"If we know which regions are associated with PTSD, then we can begin to focus interventions such as brain stimulation on the cerebellum and potentially improve treatment outcomes," Huggins said.
The findings, published Jan. 10 in the journal Molecular Psychiatry, prompted Huggins and her lab to look for precursors: a smaller cerebellum that might make people more susceptible to post-traumatic stress disorder, or that trauma-induced post-traumatic stress disorder leads to cerebellar shrinkage.
Post-traumatic stress disorder is a mental illness caused by experiencing or witnessing a traumatic event, such as a car accident, sexual abuse, or military combat. While most people who experience trauma do not develop the disorder, about 6 percent of adults develop PTSD, which is often characterized by increased fear and reliving of the traumatic event.
Researchers found that PTSD is linked to multiple brain regions, including the amygdala, which regulates fear, and the hippocampus, a key hub for processing and transmitting memories throughout the brain. In contrast, the role of the cerebellum (Latin for "little brain") in PTSD has received less attention.
The cerebellum, a mass of cells the size of a grapefruit that looks like a remnant stuck awkwardly beneath the back of the brain, is best known for coordinating balance and choreographing complex movements like walking or dancing. But the cerebellum does much more than that.
"This is a very complex area," Huggins said. "If you look at how dense its neurons are relative to the rest of the brain, it's easy to understand that it does much more than just balance and movement."
"Dense" might be an understatement. The cerebellum accounts for only 10% of the total brain volume, but houses more than half of the brain's 86 billion nerve cells.
Researchers recently observed changes in cerebellar volume in patients with post-traumatic stress disorder. However, most of these studies are limited by small data sets (fewer than 100 participants), broad anatomical boundaries, or focus on specific patient groups, such as veterans or sexual assault victims with post-traumatic stress disorder.
To overcome these limitations, Duke's Dr. Morey joined more than 40 other research groups in a larger data-sharing initiative to pool their brain imaging scans to study PTSD as broadly and universally as possible.
The team ended up with 4,215 MRI scans of adults, about a third of whom had been diagnosed with post-traumatic stress disorder.
"I spend a lot of time studying the cerebellum," Huggins said. Even with automated software available to analyze thousands of brain scans, Huggins manually spot-checked each image to make sure the boundaries drawn around the cerebellum and its multiple subregions were accurate. The result of this comprehensive approach is a fairly simple and consistent finding: The cerebellums of people with PTSD are 2 percent smaller than those of normal people.
When Huggins zoomed in on specific areas of the cerebellum that influence mood and memory, she found similar shrinkage in the cerebellums of people with PTSD. He also found that people with more severe PTSD had smaller cerebellums: "Focusing solely on categorical diagnoses of yes or no doesn't always give us the clearest picture." When we looked at the severity of PTSD, people with more severe PTSD had even smaller cerebellums. "
These results are an important first step in studying how and in what ways PTSD affects the brain.
Huggins explained that there are more than 600,000 combinations of symptoms that can lead to a diagnosis of PTSD. It will also be important to figure out whether different combinations of PTSD symptoms affect the brain differently. For now, though, the hope is that this work will help others recognize the cerebellum as an important driver of complex behaviors and processes beyond gait and balance, and as a potential target for current new treatments for people with PTSD.
"While there are some effective treatments for people with PTSD, we know they don't work for everyone," Huggins said. "If we can better understand what's going on in the brain, then we can try to combine that information to come up with treatments that are more effective, longer-lasting, and effective for more people."
Compiled source: ScitechDaily