Adults with posttraumatic stress disorder (PTSD) have smaller cerebellums than unaffected adults, suggesting that this part of the brain may be a potential therapeutic target.
According to recent research on more than 4000 adults, cerebellum volume was significantly smaller (by about 2%) in those with PTSD than in trauma-exposed and trauma-naive controls without PTSD.
"The differences were largely within the posterior lobe, where a lot of the more cognitive functions attributed to the cerebellum seem to localize, as well as the vermis, which is linked to a lot of emotional processing functions," lead author Ashley Huggins, PhD, said in a news release.
"If we know what areas are implicated, then we can start to focus interventions like brain stimulation on the cerebellum and potentially improve treatment outcomes," said Huggins, who worked on the study while a postdoctoral researcher in the lab of Rajendra Morey, MD, at Duke University, Durham, North Carolina, and is now at the University of Arizona, Tucson.
While the cerebellum is known for its role in coordinating movement and balance, it also plays a key role in emotions and memory, which are affected by PTSD.
Smaller cerebellar volume has been observed in some adult and pediatric populations with PTSD.
However, those studies have been limited by either small sample sizes, the failure to consider key neuroanatomical subdivisions of the cerebellum, or a focus on certain populations such as veterans of sexual assault victims with PTSD.
To overcome these limitations, the researchers conducted a mega-analysis of total and subregional cerebellar volumes in a large, multicohort dataset from the Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA)-Psychiatric Genomics Consortium PTSD workgroup that was published online on January 10, 2024, in Molecular Psychiatry.
They employed a novel, standardized ENIGMA cerebellum parcellation protocol to quantify cerebellar lobule volumes using structural MRI data from 1642 adults with PTSD and 2573 healthy controls without PTSD (88% trauma-exposed and 12% trauma-naive).
After adjusting for age, gender, and total intracranial volume, PTSD was associated with significant gray and white matter reductions of the cerebellum.
People with PTSD demonstrated smaller total cerebellum volume as well as reduced volume in subregions primarily within the posterior cerebellum, vermis, and flocculonodular cerebellum than controls.
In general, PTSD severity was more robustly associated with cerebellar volume differences than PTSD diagnosis.
Focusing purely on a "yes-or-no" categorical diagnosis didn't always provide the clearest picture. "When we looked at PTSD severity, people who had more severe forms of the disorder had an even smaller cerebellar volume," Huggins explained in the news release.
Novel Treatment Target PTSD
These findings add to "an emerging literature that underscores the relevance of cerebellar structure in the pathophysiology of PTSD," the researchers noted.
They caution that despite the significant findings suggesting associations between PTSD and smaller cerebellar volumes, effect sizes were small. "As such, it is unlikely that structural cerebellar volumes alone will provide a clinically useful biomarker (eg, for individual-level prediction)."
Nonetheless, the study highlights the cerebellum as a "novel treatment target that may be leveraged to improve treatment outcomes for PTSD," they wrote.
They noted that prior work has shown that the cerebellum is sensitive to external modulation. For example, noninvasive brain stimulation of the cerebellum has been shown to modulate cognitive, emotional, and social processes commonly disrupted in PTSD.
Commenting on this research for Medscape Medical News, Cyrus A. Raji, MD, PhD, associate professor of radiology and neurology at Washington University in St. Louis, Saint Louis, Missouri, noted that this "large neuroimaging study links PTSD to cerebellar volume loss."
"However, PTSD and traumatic brain injury frequently co-occur, and PTSD also frequently arises after TBI. Additionally, TBI is strongly linked to cerebellar volume loss," Raji pointed out.
"Future studies need to better delineate volume loss from these conditions, especially when they are comorbid, though the expectation is these effects would be additive with TBI being the initial and most severe driving force," Raji added.
The research had no commercial funding. Author disclosures are listed with the original article. Raji is a consultant for Brainreader, Apollo Health, Pacific Neuroscience Foundation, and Neurevolution Medicine LLC.
This article originally appeared on Medscape