A 12-month-old healthy, normally developing boy presented with rapidly increasing head circumference over 2 months and 1 week of strabismus. Head circumference was 50 cm (.99th percentile; mother 5 59.5 cm; father 5 56.5 cm). Examination showed limited abduction OD, overshoot of adduction OD, and no papilledema. MRI ( figure) showed the right anterior inferior cerebellar artery traversing the root entry zone of the right abducens nerve, a cause of unilateral cranial nerve VI palsy recognized in adults 1 but not in children.2 Neuroimaging was otherwise normal. The patient was diagnosed with benign familial macrocephaly and discharged with ophthalmology follow-up for conservative management.Cynthia Pudukadan, MD, Prashant Shankar, MD, Cassandra White, MD, Kevin R. Gertsch, MD, Scott W. Elton, MD, C.J. Malanga, MD, PhDFrom the University of North Carolina School of Medicine, Chapel Hill. Author contributions: Cynthia Pudukadan: drafting/revising the manuscript, study concept or design, analysis or interpretation of data, accepts responsibility for conduct of research and final approval. Prashant Shankar: study concept or design, analysis or interpretation of data, accepts responsibility for conduct of research and final approval, acquisition of data, study supervision. Cassandra White: analysis or interpretation of data, accepts responsibility for conduct of research and final approval, acquisition of data. Kevin R. Gertsch: drafting/ revising the manuscript, accepts responsibility for conduct of research and final approval, acquisition of data. Scott W. Elton: drafting/revising the manuscript, accepts responsibility for conduct of research and final approval, study supervision. C.J. Malanga: drafting/revising the manuscript, study concept or design, analysis or interpretation of data, accepts responsibility for conduct of research and final approval.