(dailyRx News) It's not unusual to experience clinical depression in the months following a stroke, but scientists have not understood exactly why many stroke survivors end up depressed.
A recent study sheds light on one possible mechanism by which alterations to a network in the brain may play a part in whether a person is at a higher risk for depression after having a stroke.
Igor Sibon, MD, a neurology professor at the University of Bordeaux in France, led the study to find out possible links between depression after a stroke and changes in the brain networks.
"A third of patients surviving a stroke experience post-stroke depression (PSD)," said Dr. Sibon. "However, studies have failed to identify a link between lesions in the brain caused by ischemia during a stroke and subsequent depression."
Ischemia occurs when blood supply becomes restricted to tissues in the body and deprives the person of the oxygen and sugar to keep those tissues alive.
Dr. Sibon's team looked specifically at a group of brain structures called a "default-mode network" because changes in the connections within these networks have been seen in depressed patients.
This network is a part of the brain involved in internal thought processes, such as retrieving memories and brain processing, when the brain is not actively doing something else. It's the "default" thinking state of the brain.
Dr. Sibon and colleagues studied 24 patients, aged 18 to 80 years old, who had an functional MRI (fMRI) to measure metabolic changes in the brain 10 days after having a mild or moderate ischemic stroke.
Each patient also received a clinical evaluation for depression and anxiety both 10 days and three months after their stroke. At the three-month mark, 10 patients had mild to moderate depression and 14 had no depression.
When Dr. Sibon's team compared the fMRI exams among the depressed and non-depressed patients, they found that the amount of depression a patient was experiencing three months after their stroke was associated with modifications in the connections of the default-mode network.
"We found a strong association between early resting-state network modifications and the risk of post-stroke mood disorders," Dr. Sibon said. "These results support the theory that functional brain impairment following a stroke may be more critical than structural lesions."
Dr. Sibon said the research might help doctors determine the best clinical treatment for stroke patients who have an fMRI showing connectivity changes in their default-mode network.
The study was published online June 5 in the journal Radiology. The researchers were funded by the Région Aquitaine, the Société Française NeuroVasculaire and Association France Accident Vasculaire Cerebral.