The clinical and pathologic findings in a 10 month old girl with congenital heart diseasewho died after rupture of a congenital distal basilar artery aneurysm are reported from the University of Connecticut Health Center, Farmington, CT and the Children’s Hospital of Philadelphia, PA. She was hospitalized at 10 months of age after having had 4 syncopal episodes within a 6 week interval. Twenty-four hours after cardiac catherization the infant developed an adduction deficit of the left eye which resolved over the next 36 hours. Five days after surgical correction of the cardiac defect she had a massive subarachnoid hemorrhage. 
COMMENT. Transient third nerve paresis in an infant with a history of recurrent syncope and congenital heart disease should suggest a possible intracranial arterial aneurysm. The authors found 6 previous reports of basilar aneurysm preceded by a transient third nerve dysfunction. A migraine variant is another explanation.