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Hydrocephalus FAQ


Former Hydro Page

We have created this section on hydrocephalus frequently asked questions (FAQ) to help answer some commonly asked questions regarding CNS (central nervous system) shunts. Over time, we will add more responses and hopefully address many of the shunt issues and questions today. For the most COMPLETE hydrocephalus information, see our main section on hydrocephalus (linked below).

Visit: Main Section on Hydrocephalus Information and Advocacy

Visit: Special 2008 Hydrocephalus Study: Shunt Selection Model

Q: What's are the difference between the three available programmable shunts?

The primary differences between the available programmable shunts are in the number of available settings. The Codman Medos valve can be more finely tuned, as it has 10mm H2O increments to select from ranging 30 to 200, for a total of 18 settings. The Medtronic Strata only has 5 settings, where it's lowest setting of 0.5 is equivalent to about 50 mmH2O or so on the Codman. In comparing the Medtronic to the Codman, the cut-off opening pressure on the low end can be a problem for some patients requiring a very low setting. The Sophysa programmable comes in four different models ranging from 10 to 140 mm H2O, 30 to 200 mm H20, 50 to 300 mm H2O, and 80 to 400 mm H2O. Each has eight pressure selections to choose from. The SM8 model, with 30 to 200 mm H20, is their standard model.

Both come with different types of anti-siphon devices integrated within the valve. The Medos uses the Siphon Guard, whereas the Strata uses the SCD. However, the Strata is not available w/o SCD, whereas the Medos comes with or without its siphon guard system. It seems the majority of adults today require siphon control, perhaps a bit fewer in NPH, and it can cause problems for some. Codman's siphon guard is pretty simple and stable, though is reported to experience more obstructions due to its fine flow path. The Medtronic SCD system is very much dependent on the vertical location on the head where the valve is placed, and is recommended to be placed at “zero point,” or near the level of the top of the ear (middle of ventricles). Near the top of the head, the SCD does not flow as much when sitting or standing, and place it too low on the head and it won't retard overdrainage much at all. The nsg can “partly” offset the SCD’s upright flow control by raising or lowering the Strata setting. But at the top or bottom of the pressure selections, it's possible you will NEVER be able to get the right setting. The Codman Siphon Guard is unaffected by these issues, and it can pretty much work well on any patient. Still, both ADD additional flow resistance, and cause an effective higher opening pressure in these shunts.

As both are programmable, their settings CAN be accidentally changed by magnetic fields around the home. The only way to know which setting these two programmable shunts are set to is with a by skull x-ray. Of interest, the setting on the newer Sophysa Polaris programmable shunt can be read via the programming meter in the nsgs office. The Polaris also has a LOCKING mechanism, and is the least affected by magnetic fields. But it has does NOT come with any siphon control system. Nsgs often will attach an SCD or Shunt Assistant (Mfr Meithke) in line to control overdrainage when upright.

There are many mixed reports on how prevalent it is for programmable shunts to accidentally loose their setting from magnetic fields around the home and such. You can ask your nsg as to his/her experiences and views. Patient forums are filled with stories telling that this is happening quite often. My own experiences and study of the issue suggests it is happening more than is being reported, primarily because the only way to document when Medtronic and Codman programmable shunt looses its setting is via a skull x-ray. And the use of the x-ray procedure is more INTENDED for confirming the shunt’s setting after being programmed, rather than DOCUMENTING if and when its setting might have been changed.

My Codman Medos shunt had to be replaced after only 9 months as it was found to be frequently loosing its setting, and towards the end nearly 2-3 times a week. I was revised to the Orbis Sigma shunt (mfr Integra) that is not programmable, but termed "auto adjusting." I am more pleased with this OSV-2 and I don't have to fuss with the settings issue.

Overall, I favor the Codman Medos over the Medtronic Strata. If the Strata were more carefully chosen and specifically placed on a user’s head, it could perhaps be more reliable than the Medos with Siphon Guard. The Siphon Guard has been reported to be linked to shunt obstructions from debris as it has a very fine flow pathway.

If you're active and around a lot of electronic equipment, gaming, and household devices, I’d recommend the OSV-2 Orbis Sigma valve. If your hydrocephalus and CSF outflow requirements require a shunt valve with more CSF outflow than the OSV-2, I'd recommend the Phoenix Biomedical "Diamond Valve." This valve is somewhat of a sister valve to the Orbis Sigma, is auto adjusting, but allows a higher flow rate.