ABSTRACT
Background: Etiologies of hydrocephalus are many and sometimes it can be attributed to be multifactorial in origin. Presence of known cause of hydrocephalus like fourth ventricular pathology may mask foramenal stenosis. Diagnosis of unilateral and bilateral stenosis of foramen of Monro should be included in the treatment plan in hydrocephalus. A case report of a 9 months-old boy presented with delayed milestones of development and an increase in head circumference. The patient has been diagnosed as hydrocephalus and associated Dandy-Walker malformation. Ventriculoperitoneal shunt was inserted successfully but drained only one lateral ventricle. The association of isolated lateral ventricle with Dandy-Walker malformation is due to stenosis of foramen of Monro. Our case report is unique due to association between foramen occlusion and Dandy-Walker malformation