Operative Protocol for the Diamond Valve
in Pediatric and Adult Hydrocephalus
Courtney Smith, MS

Abstract
During the past forty years hydrocephalus has largely been treated by the implantation of constant resistance, differential pressure valves. Although these valves seemed to work for some patients, many others suffered from complications, such as infection, occlusion, migration, overdrainage and underdrainage. In 1987 Christian Sainte-Rose introduced the concept of flow regulation by varying valve resistance with the Orbis-Sigma Valve. The Orbis-Sigma has demonstrated itself to be an effective treatment alternative to the traditional differential pressure mechanisms, but some limitations have been reported, such as obstruction, excessively high opening pressure and insufficient flow. A new flow-regulating valve, the CRx Diamond Valve (Phoenix Biomedical Corp, Valley Forge, PA) has been developed in an attempt to refine physiologic flow-control. Conceptually a valve mechanism that regulates flow within physiologic limits, regardless of other factors, would eliminate the need for valve pressure selection. In effect, a single valve could be used for a broad spectrum patients. The Diamond Valve is such a design.

Cerebrospinal Fluid Physiology and Shunt Performance
       Cerebrospinal fluid (CSF) is produced in the ventricles by the choroid plexus. The normal physiologic production rate of CSF is approximately 0.15 ml/min at birth and this rate gradually rises to 0.33ml/min by the age of 2 or 3. Although this rate can vary from patient to patient, this variance is only about 0.05 ml/min.9,26 Although production of CSF in the ventricles is relatively constant and is not directly affected by changes in posture or activity, intraventricular pressure (IVP) is never constant. Changes in activity and posture, and even REM sleep, will result in significant pressure changes within the ventricles.8,23 Following production the CSF circulates from the ventricles through the subarachnoid spaces of the central nervous system (CNS) and is ordinarily taken into the blood stream via the arachnoid villi. Hydrocephalus results from a disturbance in this critical balance between production and absorption of CSF.

      Since 1956 with the invention of the first functioning hydrocephalus shunt by John Holter, DSc., hydrocephalus has been treated primarily with differential pressure valves that maintain a constant resistance to flow. In differential pressure (DP) valves, the pressure inside the ventricles is maintained at a fairly constant value, dependant upon blood flow but independent of patient position or activity. In addition, problems like