This multicenter, prospective study of children with hydrocephalus will examine whether or not ventricle size is associated with poor cognitive outcomes. It is expected that results will indicate larger ventricular size at 6 months after surgery for the initial treatment of hydrocephalus will relate to poorer cognitive outcomes. This study is being conducted by the Hydrocephalus Clinical Research Network (HCRN), a network established to conduct multi-institutional clinical trials on pediatric hydrocephalus.

The current literature is inconclusive regarding the direct association between large ventricle size and poorer cognitive outcomes. This uncertainty stems from relatively few studies, problems with study design (possible confounding factors), varying study populations of hydrocephalus, and conflicting evidence. If the association is proven then aggressive strategies must be developed to maximally decrease ventricular size in these children to preserve long-term cognitive functioning. However, if the association is disproven then previous reservations for procedures such as Endoscopic Third Ventriculostomy (ETV) or higher-resistance shunting to prevent overdrainage complications will be further minimized. Either finding has a major potential to further improve the quality of life in our pediatric hydrocephalus patients. This study is unique as it will include pediatric patients presenting with hydrocephalus from a wide range of etiologies. This study is also unique in that we propose to conduct a brief pre-operative neuropsychological examination to act as internal controls along with the outcomes obtained at a more extensive neuropsychological examination at six months after initial hydrocephalus treatment surgery.

Inclusion Criteria: Patients will be eligible for enrollment if they:

• are 5 years of age or older; and
• have been newly diagnosed with hydrocephalus to be managed surgically with either a cerebrospinal fluid (CSF) shunt or an ETV; and
• have one of the following etiologies for hydrocephalus: aqueductal stenosis, supratentorial and posterior fossa tumors both benign and malignant, post-traumatic, myelomeningocele, tectal gliomas, post-infectious, and following spontaneous intraventricular hemorrhage (IVH). Malignant tumors have been included as the neuropsychological deficits secondary to adjuvant chemotherapy and radiation have not been demonstrated within the proposed study's 6 month window.

Exclusion Criteria: Patients will be ineligible for enrollment if ANY of the following is true or anticipated:

• present with a Glasgow Coma Scale (GCS) score of less than 14/15, cerebellar mutism, or cognitive deficits so severe as to make neuropsychological testing impossible; OR
• have etiologies of diffuse intrinsic pontine glioma, atypical teratoid rhabdoid tumor, or any tumor with cerebral or spinal metastases (these patients' clinical course and survival are highly unpredictable); OR
• are not expected to survive for 6 months; OR
• are unable or unwilling to participate in the study and with the neuropsychological exam; OR
• due to limitations of neuropsychological testing, blind and deaf children will be excluded. Children for whom English is not their primary language will be included if they have attended 1 or more years of English language based schooling.

Pediatric, school-aged patients presenting with a first time diagnosis of hydrocephalus.