The ETCHES I Study (Endovascular Treatment of Communicating Hydrocephalus With an Endovascular Shunt)

Inclusion Criteria: 1. Age \> 18 2. Subject provides Informed Consent (IC) 3. Post-aneurysmal SAH with Hunt and Hess Grades I-IV with EVD in place with the need for a permanent CSF shunt determined through a failed EVD clamping trial defined as: 1. Post-clamping ICP of \> 20 cmH2O for 15 min, or 2. Post-clamping ICP \> 25 cmH2O for \< 15 min with patient intolerance to EVD clamping 3. Post-clamping ICP \>15 cmH2O for 15 min with radiographic evidence of ventriculomegaly 4. Clinical signs and symptoms of communicating hydrocephalus 5. Neurologically stable without evidence of severe vasospasm 6. Pre-procedure MRI with gadolinium confirmation of IPS (inferior petrosal sinus) and CPA (cerebellopontine angle) cistern anatomy suitable for eShunt Implant deployment as confirmed by SSC (subject screening committee) 7. Pre-procedure CT confirmation of no obstruction preventing CPA cistern access at target implant site (e.g., petrous bone) as confirmed by SSC Exclusion Criteria: 1. Patient is in a state of unconsciousness or is unable to understand the information provided in the Informed Consent Form for this study 2. Indication of obstructive hydrocephalus 3. Presence of gross blood in CSF from EVD 4. Pregnant 5. Unwilling or unable to comply with follow up requirements 6. Active systemic infection or infection detected in CSF 7. Life expectancy \< 1 year 8. Hypersensitivity or contraindication to heparin or radiographic contrast agents which cannot be adequately pre-medicated, desensitized or where no alternative is available 9. Occlusion or stenosis of the internal jugular vein 10. Venous distension in the neck on physical exam 11. Atrial septal defect or patent foramen ovale identified on cardiac echocardiogram 12. History of bleeding diatheses, coagulopathy or will refuse blood transfusion in cases of emergency 13. Clearly antecedent stroke unrelated to post-aneurysmal SAH 14. Patient is currently participating in another investigational drug or device trial that could conflict with study data collection or follow-up 15. Other medical illnesses that may cause the patient to be non-compliant with the protocol or confound data interpretation as determined by the study Investigator 16. Presence of a deep vein thrombosis superior to the popliteal segment of the femoral vein 17. International Normalized Ratio (INR) or Partial Thromboplastin Time (PTT) results outside of normal range (INR 0.8-1.4; PTT 25-35 secs.)