Hydrocephalus Shunts The development of the biocompatible silicone elastomer – a type of plastic that could be implanted in the human body – allowed the introduction of hydrocephalus shunts. The first clinically-viable, valve-regulated hydrocephalus shunt, introduced in 1952, ushered in the modern era of hydrocephalus surgery and treatment. At that time, there was no effective medical intervention for hydrocephalus. In that year, two neurosurgeons working in conjunction with a hydraulics technician whose child had hydrocephalus, successfully implanted a silicone elastomer, ventriculojugular shunt regulated by a ball-in-spring valve design inserted at either end of a flexible piece of tubing. This device regulated and released controlled amounts of the cerebrospinal fluid (CSF) from the brain into the heart’s right atrium. At about the same time, another neurosurgeon produced a one-way slit valve made of silicone elastomer. The development of the valve system combined with the application of new biocompatible materials allowed for the safe and reliable diversion of CSF without many of the complications of unregulated (systems without valves) CSF drainage. Other neurosurgeons soon introduced the concept of ventriculoperitoneal procedures, the distal end of the tubing ending in the abdominal cavity, in which these newer devices were used. While the early shunts allowed for the management of hydrocephalus, patients still faced numerous repeat surgeries due to shunt malfunction and/or shunt infection. Focus turned to the creation of a more sophisticated valve mechanism that would control the rate of CSF flow through the shunt, taking into account the variables caused by regular daily activity. The 1970s saw the introduction of valves that addressed overdrainage or siphoning of CSF caused by an individual’s postural (standing, sitting, or lying down) change and vasogenic (blood flow) influences. As an example, moving to a standing posture causes a siphon or sucking effect, essentially “pulling” fluid out of the brain or lumbar region. The anti-siphon device was introduced in the early 1970s, followed by the gravity compensating mechanism in 1976. Flow regulated shunts were introduced in 1987. These valves maintain the drainage flow rate close to the rate of CSF secretion, regardless of patient position and other conditions that normally promote overdrainage. The problem remained that when these devices were not draining fluid properly, the individual had to undergo brain surgery to adjust or replace the shunt. The mid-1980s heralded in the programmable shunt. These shunts can be adjusted noninvasively using a magnet. The first magnetically-adjustable valve was marketed in 1984. Advances also addressed reducing infection rates both during and after surgery. In 1976, the first commercially-sterilized shunt came to market. Antibacterial catheter coatings became commercially available in 2001. These advances in shunt construction have been coupled with standardized procedures produced by the Hydrocephalus Clinical Research Network (HCRN) that have dramatically reduced infection rates in the pediatric population. There are now literally hundreds of options for valves, proximal and distal catheters. Further, device modifications to minimize overdrainage, antibacterial coatings, and magnetically-adjustable valves for fine-tuning CSF flow rates, are all evolutionary modifications of the original clinically-viable shunt design. Progress in imaging technology has allowed clinicians to treat hydrocephalus with greater success and safety. In the 1980s endoscopes again found a role in neurosurgery. The benefits include more accurate placement of ventricular catheters and creation of third ventriculostomies, primarily for aqueductal stenosis, in carefully-screened patients. Stereotactic localization, a minimally invasive surgical technique, led to more functional and safer approaches for the CSF drainage.
Posted on: Tue, 06 Aug 2013 16:39:41 +0000
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