Snapshot An infant boy is brought to the emergency department due to lethargy and enlarging head circumference. The parents deny any recent infections or trauma to the patient. They report he had 2 episodes of emesis and is inconsolable. On physican exam, head circumference is larger than expected. An MRI of the head is performed, which shows aqueductal funnelling and enlargment of the lateral and third ventricles. (Congenital aqueductal stenosis) Introduction Clinical definition narrowing of the cerebral aqueduct Epidemiology incidence most common cause of congenital obstructive hydrocephalus Pathogenesis narrowing of the cerebral aqueduct results in increased cerebral spinal fluid volumes in the ventricular system resulting in obstructive hydrocephalus etiologies include congenital narrowing of the cerebral aqueduct compression (e.g., malignancy and vascular malformation) hemorrhage infection see CSF topic for synthesis/resorption pathway Presentation Symptoms headache vomiting decrease consciousness hyperreflexia Physial exam macrocephaly newborn skulls are not fused allowing the head circumference to expand upward gaze palsy Imaging MRI indication performed to further evaluate the cause of probable hydrocephalus based on history and physical exam findings enlargement of the lateral and third ventricles Treatment Operative ventriculostomy indication a treatment option for communicating hydrocephalus ventriculoperitoneal shunt indication a treatment option for communicating hydrocephalus