Isolated Upper-Extremity Monoparesis From Basal Ganglia Infarction in a Child With Congenital Internal Carotid and Anterior Cerebral Artery Agenesis: A Case Report.

Pediatric stroke is rare and presents with diverse clinical manifestations, often causing delayed recognition and significant long-term morbidity. Isolated upper-extremity monoparesis secondary to basal ganglia infarction in the context of congenital internal carotid artery (ICA) and anterior cerebral artery (ACA) agenesis is extremely uncommon. We report a 14-year-old male presenting with acute left upper-extremity monoparesis. Brain MRI with MRA revealed an acute basal ganglia infarction and congenital agenesis of the right distal ICA and ACA with collateral circulation. Despite well-developed collaterals, ischemia occurred in the lenticulostriate territory, highlighting the vulnerability of subcortical end-arterial regions. The patient had no conventional stroke risk factors, and the subtle neurological deficit underscores the risk of delayed diagnosis. He received antithrombotic therapy, statin therapy, and supportive care, achieving partial neurological recovery. This case highlights the need to consider central causes in children with focal limb weakness and illustrates congenital ICA and ACA agenesis as rare but clinically important contributors to pediatric ischemic stroke.