The authors report the case of a 25-month-old boy who underwent endoscopic third ventriculostomy (ETV) for hydrocephalus resulting from aqueductal stenosis. The patient's recovery was monitored longitudinally and prospectively using MR diffusion tensor imaging (DTI) and formal neuropsychological testing. Despite minimal change in ventricle size, improvement in the DTI characteristics and neurodevelopmental trajectory was observed following ETV. These data support the use of DTI as a biomarker to assess therapeutic response in children undergoing surgical treatment for hydrocephalus. In the patient featured in this report, DTI appeared to provide more information regarding postoperative neurodevelopmental outcome than ventricle size alone.