Patwardhan, et al, Implanted Ventricular Shunts in the United States: The Billion-dollar-a-year Cost of Hydrocephalus Treatment, Neurosurgery 56:139-145, 2005 Patwardhan, et al, Implanted Ventricular Shunts in the United States: The Billion-dollar-a-year Cost of Hydrocephalus Treatment, Neurosurgery 56:139-145, 2005