Risk factors in 212 children (54% male; median age 5 years) presenting with a first arterial ischemic stroke (AIS) over 22 years were studied at Great Ormond Street Hospital for Children, London, UK. Patients were grouped as 1) symptomatic AIS (97), at risk because of a preceding medical diagnosis; and 2) previously healthy (115). Cerebral arterial imaging in 185 (87%) (including 115 previously healthy patients) was abnormal in 79%. Echocardiography in 104 previously healthy patients was abnormal in only 8. A comparison of the prevalence of trauma, infection, fever, varicella zoster within previous year, and hypertension within the 2 groups showed 2 significant differences: 1) trauma within previous 2 weeks was more common in the previously healthy group (23/115 cf 2/97 symptomatic); and 2) previous v. zoster was more likely in previously healthy group (68/105 cf 31/71 symptomatic). Cerebral arterial abnormalities, previous v. zoster infection, preceding trauma, recent infection, and anemia are common findings in children with AIS. Previously undetected structural cardiac abnormalities are rare. A previous medical diagnosis was identified in approximately one half. Hypertension was recognized in approximately 50%; anemia in 40%; and elevation of total plasma homocysteine or homozygosity for the MTHFR mutation in 21%. Prothrombotic screening is commonly negative. 
COMMENT. Risk factors and precipitating triggers for arterial ischemic stroke in children may be identified by clinical history and examination. Cerebral arterial imaging is usually abnormal, and some risk factors such as anemia and hyperhomocysteinemia (Hhcy) may be modifiable. Identification of all risk factors is important. Hhcy may be due to cystathionine b-synthase deficiency.