Among stroke patients, there appears to be a strong link between functional impairment in a brain network responsible for emotional regulation and the severity of post-stroke depression, according to a study published online in the journal Radiology.
“A third of patients surviving a stroke experience post-stroke depression (PSD),” said lead researcher Igor Sibon, M.D., Ph.D., professor of neurology at the University of Bordeaux in France.
“However, studies have failed to identify a link between lesions in the brain caused by ischemia during a stroke and subsequent depression.”
Rather than look for dysfunction in a single area of the brain after a stroke, Dr. Sibon wanted to analyze a group of brain structures that are part of a network called the default-mode network (DMN).
Changes in connectivity in the DMN — which is associated with the internal thought process — have been observed in people with depression.
“The default-mode network is activated when the brain is at rest,” Dr. Sibon said. “When the brain is not actively involved in a task, this area of the brain is engaged in internal thoughts involving self-related memory retrieval and processing.”
For the study, 24 individuals ages 18 to 80 were given resting-state functional magnetic resonance imaging (fMRI) tests 10 days after having mild to moderate ischemic stroke. An fMRI test measures metabolic changes in specific areas of the brain. Although many fMRI exams measure brain changes while a patient performs a specific task, during a resting-state fMRI test, patients lie motionless.
The participants, including 19 men and five women, were clinically evaluated 10 days and three months post-stroke to determine the presence and severity of depression and anxiety symptoms. At three months post-stroke, patients were evaluated for depression using the DSM-IV diagnostic classification system.
Using the DSM-IV criteria, 10 patients had minor to moderate depression, and 14 patients had no depression. The fMRI exams showed an association between changes in connectivity in the DMN 10 days after stroke and the severity of depression three months post-stroke.
“We found a strong association between early resting-state network modifications and the risk of post-stroke mood disorders,” Sibon said. “These results support the theory that functional brain impairment following a stroke may be more critical than structural lesions.”
The widespread chemical changes triggered by a stroke may lead to changes in connectivity in brain networks such as the DMN, said Sibon. He added that these study results may show physicians how to help treat post-stroke patients whose fMRI results indicate impaired connectivity in the DMN.