The blood cells in sickle cell disease are abnormally shaped  (sickle-shaped) and may form clots or block blood vessels. Estimates of children with sickle cell anemia who suffer strokes (with silent strokes predominating in the younger patients) range from 15%-30%. These children are at significant risk of cognitive impairment and poor educational outcomes. Thalassemia major: is an autosomal recessive genetically inherited form of hemolytic anemia, characterized by red blood cell (hemoglobin) production abnormalities. Children with this disorder are at increased risk for silent stroke. Atrial fibrillation (AF): atrial fibrillation (irregular heartbeat) is associated with a doubled risk for silent stroke. Cigarette smoking: The procoagulant and atherogenic effects of smoking increase the risk for silent stroke. Smoking also has a deleterious effect on regional cerebral blood flow (rCBF). The chances of having a stroke increase with the amount of cigarettes smoked and the length of time an individual has smoked (pack years). C-reactive protein (CRP) and Interleukin 6 (IL6): C-reactive protein is one of the plasma proteins known as  acute phase proteins (proteins whose plasma concentrations increase (or decrease) by 25% or more during inflammatory disorders) which is produced by the liver. The level of CRP rises in response to inflammation in various parts of the body including vascular inflammation. The level of CRP can rise as high as 1000-fold in response to inflammation. Other conditions that can cause marked changes in CRP levels include infection, trauma, surgery, burns, inflammatory conditions, and advanced cancer. Moderate changes can also occur after strenuous exercise, heatstroke, and childbirth.
Sleep apnea: encompasses a heterogeneous group of sleep-related breathing disorders in which there is repeated intermittent episodes of breathing cessation or hypopnea, when breathing is shallower or slower than normal. Sleep apnea is a common finding in stroke patients but recent research suggests that it is even more prevalent in silent stroke and  chronic microvascular changes in the brain. In the study presented at the American Stroke Associations International Stroke Conference 2012 the higher the apnea-hypopnea index, the more likely patients had a silent 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 Ravens 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.