Stroke with no outward symptoms associated with stroke
Medical condition
A silent stroke (or asymptomatic cerebral infarction) is a stroke that does not have any outward symptoms associated with stroke, and the patient is typically unaware they have suffered a stroke. Despite not causing identifiable symptoms, a silent stroke still causes damage to the brain and places the patient at increased risk for both transient ischemic attack and major stroke in the future. In a broad study in 1998, more than 11 million people were estimated to have experienced a stroke in the United States. Approximately 770,000 of these strokes were symptomatic and 11 million were first-ever silent MRI infarcts or hemorrhages. Silent strokes typically cause lesions which are detected via the use of neuroimaging such as MRI. The risk of silent stroke increases with age but may also affect younger adults. Women appear to be at increased risk for silent stroke, with hypertension and current cigarette smoking being amongst the predisposing factors.
These types of strokes include lacunar and other ischemic strokes and minor hemorrhages. They may also include leukoaraiosis (changes in the white matter of the brain): the white matter is more susceptible to vascular blockage due to reduced amount of blood vessels as compared to the cerebral cortex. These strokes are termed "silent" because they typically affect "silent" regions of the brain that do not cause a noticeable change in an afflicted person's motor functions such as contralateral paralysis, slurred speech, pain, or an alteration in the sense of touch. A silent stroke typically affects regions of the brain associated with various thought processes, mood regulation and cognitive functions and is a leading cause of vascular cognitive impairment and may also lead to a loss of urinary bladder control.
In the Cardiovascular Health Study, a population study conducted among 3,660 adults over the age of 65, 31% showed evidence of silent stroke in neuroimaging studies utilizing MRI. These individuals were unaware they had suffered a stroke. It is estimated that silent strokes are five times more common than symptomatic stroke.
A silent stroke differs from a transient ischemic attack (TIA). In TIA, symptoms of stroke are exhibited which may last from a few minutes to 24 hours before resolving. A TIA is a risk factor for having a major stroke and subsequent silent strokes in the future.
Risk factors.
There are various individual risk factors associated with having a silent stroke. Many of these risk factors are the same as those associated with having a major symptomatic stroke.
Neuropsychological deficits.
Individuals who have had silent strokes often have various neuropsychological deficits and have significant impairment in multiple areas of cognitive performance. One study has shown an association between silent stroke and a history of memory loss and lower scores on tests of cognitive function. In a second study, individuals who have a had a silent stroke scored lower on the mini–mental state examination (MMSE) and on Raven's Colored Progressive Matrices—a test designed for children aged 5 through 11 years, mentally and physically impaired individuals, and elderly people.
In children.
Children who have suffered silent strokes often have a variety of neuropsychological deficits. These deficits may include lowered I.Q., learning disabilities, and an inability to focus.
Silent strokes are the most common form of neurologic injury in children with sickle cell anemia, who may develop subtle neurocognitive deficits in the areas of attention and concentration, executive function, and visual-motor speed and coordination due to silent strokes which may not have been detected on physical examination.
Link to depression.
Major depression is a risk factor and also a consequence of silent brain infarction (SBI). Persons who present with symptoms of presenile and senile major depression showed a markedly higher incidence of SBI (65.9% and 93.7%). Individuals with major depression who have had an SBI present with more marked neurological deficits and more severe depressive symptoms than do those without SBI.
Diagnosis.
The diagnosis of a silent stroke is usually made as an incidental finding (by chance) of various neuroimaging techniques. Silent strokes may be detected by:
Prevention.
Preventive measures that can be taken to avoid sustaining a silent stroke are the same as for stroke. Smoking cessation is the most immediate step that can be taken, with the effective management of hypertension the major medically treatable factor.
Sickle cell anemia.
Transfusion therapy lowers the risk for a new silent stroke in children who have both abnormal cerebral artery blood flow velocity, as detected by transcranial Doppler, and previous silent infarct, even when the initial MRI showed no abnormality. A finding of elevated TCD ultrasonographic velocity warrants MRI of the brain, as those with both abnormalities who are not provided transfusion therapy are at higher risk for developing a new silent infarct or stroke than are those whose initial MRI showed no abnormality.
References.
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