Washington: Scientists have found a strong association between the severity of post-stroke depression and impairments in a network of the brain involved in emotional regulation.
The findings, published online in the journal Radiology, may contribute to the clinical management of stroke patients by providing an opportunity to investigate the effects of a variety of treatments, the researchers said.
"A third of patients surviving a stroke experience post stroke depression (PSD).
However, studies have failed to identify a link between lesions in the brain caused by ischemia during a stroke and subsequent depression," said lead researcher Igor Sibon at the University of Bordeaux in France.
Instead of looking for dysfunction in a specific area of the brain following a stroke, Dr Sibon`s study was designed to assess a group of brain structures organised in a functional network called the default-mode network (DMN).
Modifications of connectivity in the DMN, which is linked with internally generated thought processes, has been observed in depressive patients.
"The default-mode network is activated when the brain is at rest. When the brain is not actively involved in a task, this area is engaged in internal thoughts involving self memory retrieval and processing," Dr Sibon said.
In the study, a group of patients underwent resting-state functional magnetic resonance imaging (fMRI) 10 days after having mild to moderate ischemic stroke. An fMRI imaging study measures metabolic changes in specific areas of the brain.
The patients were also clinically evaluated 10 days and three months post-stroke to evaluate the presence and severity of depression and anxiety symptoms. At 3 months post-stroke, patients were assessed for depression. It was found that 10 patients had moderate depression, while 14 patients had no depression.
Results of the fMRI exams revealed an association between modifications of connectivity in the DMN 10 days after stroke and the severity of depression three months post-stroke. Dr Sibon said: "We found a strong association between early resting-state network modifications and the risk of post-stroke mood disorders.
"These results support the theory that functional brain impairment following a stroke may be more critical than structural lesions."
According to Dr Sibon, the widespread chemical changes that result from a stroke may lead to the modification of connectivity in brain networks such as the DMN.
The results of the study may contribute to the clinical management of stroke patients by providing an opportunity to investigate the effects of a variety of treatments on patients whose fMRI results immediately post-stroke indicate impaired connectivity in the DMN, he added.