"Silent Stroke" Linked To Depression

A silent stroke occurs when small blood vessels in the brain become blocked or rupture. They are called silent strokes because they are not accompanied by the classic warning signs of stroke such as severe headaches, dizziness or loss of motor skills. Individuals often don't realize they've even had a stroke. Over time, these smaller blood vessels are unable to deliver blood or oxygen to the brain, and cells die. Eventually, an individual may develop problems with memory or concentration and may even have difficulty walking.

"Depression may indicate the presence of small blockages, called lesions, of the blood vessels in the brain that could provide a warning of a potential stroke before it happens," says the study's lead author, David C. Steffens, M.D., assistant professor of psychiatry at Duke University Medical Center in Durham, N.C.

Researchers say the findings suggest that individuals, especially those at risk for stroke, need to be carefully monitored for depression. Depression may indicate that a silent stroke has already occurred. Further work is needed to see if individuals with silent strokes are at risk to develop larger strokes and vascular dementia -- a condition of memory loss and other cognitive problems that result from stroke.

Although earlier studies suggested a link between depression and brain injury, most of those were small. The Duke study examined more than 3,600 elderly individuals enrolled in the Cardiovascular Health Study, which recruited subjects from Medicare lists in four communities -- Forsyth County, N.C.; Sacramento County, Calif.; Washington County, Md.; and Pittsburgh, Pa. The patients agreed to have magnetic resonance imaging (MRI) performed as part of the study. An MRI is a non-invasive imaging technique that allows physicians to view the brain. Each subject also answered a questionnaire to measure depressive symptoms experienced in the previous week.

Silent strokes were diagnosed by examining lesions in the basal ganglia, also called the 'subcortical gray matter.' Located deep within the brain, the basal ganglia acts as a relay station between different parts of the brain by producing chemicals such as serotonin and norepinephrine. These regulate the area of the brain known as the cortex, where information is processed.

"These small lesions that we found deep in the brain may represent a kind of breakdown in the connection between the basal ganglia and the cortex," Steffens says.

The number of small lesions, less than 3 millimeters in diameter, in the basal ganglia was significantly associated with depressive symptoms. The lesions appear to be caused by small strokes.

The researchers divided the subjects into four groups based on their scores on the depression questionnaire. By comparing the least and the most depressed, they determined that having basal ganglia lesions increased the risk of reporting severe depression by 40 percent, he says.

"Depression is often overlooked in the elderly because its symptoms may differ from those seen in younger people," Steffens explains. "Their depression may be more characteristically marked by apathy, a loss of interest in their usual activities, instead of sadness. So, as a result, neither the patients, their families nor their physician, may recognize these characteristics as signs of clinical depression. Patients with risk factors for heart attack and stroke need to be closely monitored for the development of depression," says Steffens.

Co-authors include: Michael J. Helms, B.S.; K. Ranga Rama Krishnan, M.D.; and Gregory L. Burke, M.D.