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Stroke denotes the sudden onset of a focal neurologic deficit
and most often includes the abrupt appearance of weakness. Interruption
of blood flow to a part of the central nervous system (CNS) usually
underlies the resultant weakness. Because most strokes in children
are related to focal cerebral involvement, the most common clinical
manifestation is the abrupt appearance of hemiparesis. Less frequently,
the cause of stroke involves the brainstem, cerebellum, or spinal cord.
The functional consequences always reflect the neuroanatomic features
of the affected CNS region. Either focal cerebral ischemia or hemorrhage
may cause the clinical manifestations of stroke. Further, ischemic
stroke in children is attributable to either arterial ischemic stroke (AIS)
or to cerebral sinovenous thrombosis (CSVT). This chapter addresses
these causes of focal cerebral injury in children. First, epidemiologic
features of stroke in children will be presented. Consideration
will then be directed to the occurrence of pediatric cerebrovascular
disease in neonates as well as in older children. Emphasis will
be placed on the pathogenetic, clinical, diagnostic, and therapeutic
aspects of the varied causes of strokes in children.
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Stroke in children follows a biphasic pattern of occurrence.
Its occurrence is highest among newborns and occurs less frequently in
children greater than 30 days of age. Among neonates, studies indicate
an occurrence of stroke that approximates a frequency of 1 in 4000
births.1-3 Arterial ischemic stroke accounts for 80% of
these occurrences, although 20% are due tocerebral
sinovenous thrombosis (CSVT) and hemorrhage (excluding intraventricular
and subarachnoid hemorrhages).4,5
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Several studies of stroke in children older than age 1 month,
performed over the last three decades have reported an occurrence
of stroke at a rate of approximately 2 in 100,000 per year.6-8 However,
recent studies suggest that the frequency may be greater and as
high as 13 in 100,000 per year.5,9 Strokes occur more often
in males than in females and more frequently in African Americans
and Caucasians.
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Ischemic injury to the brain occurs as a result of one of three
different mechanisms: embolism, thrombosis, or diminished systemic
perfusion. Embolic damage to the brain occurs when material formed
at a site in the vascular system proximal to the brain lodges in
a blood vessel, blocking cerebral perfusion. Emboli originate most
commonly from the heart, arising from clots on cardiac chamber walls
or from vegetations on valve leaflets. Congenital heart disease that
includes right-to-left shunt predisposes to such embolus formation.
Artery-to-artery emboli are composed of clot or platelet aggregates that
originate in vessels proximal to the brain but ultimately come to
rest and to occlude flow in vessels critical for cerebral perfusion.
Intravascular embolus formation is promoted by some forms of thrombophilia
(see below). Thrombosis denotes vascular occlusion resulting from
a localized process within a blood vessel or vessels. Although atherosclerosis underlies
most thrombotic processes affecting adults, it is a very uncommon
cause of thrombosis in children. Localized luminal clot formation occurs
in ...