"A third of patients surviving a stroke experience post-stroke depression (PSD)," said lead researcher Doctor Igor Sibon of the University of Bordeaux, France. "However, studies have failed to identify a link between lesions in the brain caused by ischemia during a stroke and subsequent depression."
Instead of looking for dysfunction in a specific area of the brain following a stroke, 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 associated with internally generated thought processes, has been observed in depressive patients.
"The default-mode network is activated when the brain is at rest," 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."
In the study, 24 patients between the ages of 18 and 80 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. Although many fMRI exams are designed to measure brain changes while a patient performs a specific task, during a resting-state fMRI exam, patients lie motionless.
The patients, which included 19 men and five women, were also 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. 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.
"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."
MEDICA.de; Source: Radiological Society of North America