ORIGINAL ARTICLE Neurosurgical conditions and procedures in infancy are associated with mortality and academic performances in adolescence: a nationwide cohort study Tom G. Hansen 1,2 , Jacob K. Pedersen 3 , Steen W. Henneberg 4 , Neil S. Morton 5 & Kaare Christensen 3,6,7 1 Department of Anesthesia and Intensive Care, Odense University Hospital, Odense C, Denmark 2 Clinical Institute – Anesthesiology, University of Southern Denmark, Odense C, Denmark 3 Institute of Public Health – Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark 4 Department of Anesthesia, The Juliane Marie Center, Copenhagen University Hospital – Rigshospitalet, Copenhagen, Denmark 5 Department of Anesthesia, Royal Hospital for Sick Children, Glasgow, UK 6 Department of Clinical Biochemistry and Pharmacology, University of Southern Denmark, Odense C, Denmark 7 Department of Clinical Genetics, University of Southern Denmark, Odense C, Denmark Keywords age: infant; neonates; neurosurgery; neurodevelopment; outcome Correspondence Tom G. Hansen, MD, PhD, Department of Anesthesia and Intensive Care, Odense University Hospital, DK-5000 Odense C, Denmark Emails: tom.g.hansen@rsyd.dk; tomghansen@dadlnet.dk Section Editor: Brian Anderson Accepted 28 August 2014 doi:10.1111/pan.12533 Summary Background: Few human cohort studies on anesthesia-related neurotoxicity and the developing brain have focused on and compared specific surgeries and conditions. These studies cannot disentangle the effects of anesthesia from those of the surgery and underlying conditions. This study aimed at assessing the impact of specific neurosurgical conditions and procedures in infancy on mortality and academic achievements in adolescence. Methods: A nationwide unselected register-based follow-up study of the Danish birth cohorts 1986–1990 compared academic performances of all chil- dren having undergone neurosurgeries as infants with a randomly selected, age-matched 5% sample of the same cohorts. The two groups were compared regarding mortality prior to June 1st, 2006, average test scores at ninth grade, and finally the proportion of children not attaining test scores. Results: The exposure group comprised 228 and the control group 14 698 individuals. Hydrocephalus (n = 130), craniotomy (n = 43), and myelomenin- gocele/encephalocele children (n = 55) had a higher mortality (18.5.0%, 18.6%, and 7.3%, respectively) vs controls (1.3%; P < 0.00001, P < 0.00001, and P = 0.0052, respectively). Average test scores were significantly lower than controls in hydrocephalus and craniotomy (P = 0.0043 and P = 0.0077) but not myelomeningocele/encephalocele children (P = 0.2785); the propor- tion of available test scores were significantly lower in all three groups (40.8%, 60.0%, and 67.3%, respectively) vs 86.8% in controls (P < 0.00001, P = 0.000077, and P = 0.000064). Conclusion: Neurosurgery in infancy was associated with high mortality and significantly impaired academic achievements in adolescence. When studying anesthesia-related neurotoxicity and the developing brain, focus on specific surgeries/conditions is important. Pooling of major/minor conditions and major/minor surgeries should be avoided. © 2014 John Wiley & Sons Ltd 1 Pediatric Anesthesia ISSN 1155-5645