What are silent strokes?
Author: Dr V Sathish Kumar, Senior Neurophysician, Gleneagles Global Health City,
Chennai, Silent stroke is likely caused by a blood clot that interrupts blood flow in the brain. It’s a risk factor for future strokes and a sign of progressive brain damage. Silent stroke is often incidentally detected during evaluation of any patient with an MRI. Silent stroke which infers a silent brain infarct confers an approximately 3-fold increased risk of future stroke. This is common in both patients with prior stroke and stroke-free patients. Approximately one in five asymptomatic individuals in the previous studies has showed silent brain infarcts.
There are some guidelines on how to manage patients with incidentally found silent brain infarct. The silent brain infarcts presenting clinically depends on the area of the brain involved. If the area involves the major tracts, the patient becomes disabled which alarms treatment. However, if the area does not involve any long tracts or major functional area the patient remains asymptomatic. As the risk of subsequent stroke is higher in patients with silent brain infarcts, they should be evaluated and treated as aggressively as patients with a clinical stroke.
Silent cerebrovascular disease is generally diagnosed by brain CT and MRI scans. MRI is superior to CT as it has higher sensitivity and specificity and it can better differentiate and demonstrate lacunar infarcts, small cortical and sub cortical infarction, WMHs, brain atrophy, perivascular spaces and any other structural abnormalities.
There is a strong relationship of silent brain infarcts with age and other risk factors. This suggests that they may themselves be a risk factor for future cerebrovascular events. Many studies have previously seen the rate of silent infarcts in various diseases. Upto 30% of patients with acute ischemic strokes have silent infarcts.
The main concern is the risk of recurrent stroke and vascular dementia. Many prior studies also reveal that the global cognitive function is worse significantly in patients with silent brain infarcts. If an individual has recurrent silent strokes, it can cause significant and permanent damage. They can lead to cognitive decline and dementia, with a severe impact on memory.
As there is no overt clinical impairment, silent brain infarction is poorly understood and under investigated entity. Progression of silent brain infarcts is associated with progression of cognitive decline, however, if prevention of silent brain infarcts can prevent cognitive decline is still not known. Due to this it is still unclear if MRI of brain is must to look for silent stroke in all patients. There are several challenges to screening for silent brain infarcts as there is lack of evidence for definitive treatment. Not only in adults, but even in children with sickle cell disease, silent strokes are prevalent.
Atrial fibrillation, the most common form of irregular heartbeat in people older than 65, increases the risk of silent strokes more than two-fold. Risk factors for silent stroke are also risk factors for AF. Factors that may increase your risk of stroke include high blood pressure, high cholesterol, diabetes, smoking, more-than-moderate drinking. To reduce your risks, you might take antiplatelet medications (aspirin, for example, or blood thinners if prescribed by your physician), stop using tobacco, begin an exercise program and work toward a healthy weight.