Comparison of EVD Catheter Diameter on Occlusion and Replacement

Inclusion Criteria: * Adult patients (18-85 years old) with a Glasgow Coma Scale (GCS) score of 7 or higher requiring frontal EVD placement. * Diagnoses: spontaneous subarachnoid hemorrhage, intraventricular hemorrhage, intraparenchymal or cerebellar hemorrhage due to aneurysm, arteriovenous malformation, arteriovenous fistula, hypertension, or idiopathic etiology. * Also included are patients for whom the attending neurosurgeon decides that frontal EVD placement is indicated for patient treatment with planned cerebrospinal fluid (CSF) drainage for 72 hours or more. Exclusion Criteria: * GCS of 6 or less * Hunt and Hess subarachnoid hemorrhage grade of 5. * Age 86 or greater, or age 17 or less. * Patient cannot consent and next of kin cannot consent prior to procedure. * Diagnosis of traumatic brain injury, as the EVD is often clamped for extended periods of time. * Patients anticoagulated prior to admission with warfarin, Effient, Plavix, therapeutic heparin infusion, therapeutic subcutaneous lovenox, therapeutic subcutaneous arixtra, or other therapeutic anticoagulant or antiplatelet agent (ASA not included). * Plan for EVD placement through non-frontal burr hole.