Here are some cognitive and emotional symptoms associated with NPH patients.
Hydrocephalus, the build-up of fluid in the brain, is typically relieved with a shunt that diverts cerebrospinal fluid (CSF) to either the abdominal cavity or the right atrium of the heart. Adjustable shunt valve settings allow the surgeon to select the valve’s pressure.
CSF shunt systems are commonly used to treat hydrocephalus. Uncontrolled hydrocephalus can cause symptoms including headaches, nausea, vomiting, sleepiness, failing mental function, blurred vision and loss of coordination. Left undertreated, hydrocephalus can be fatal.
Magnets can inadvertently make changes to externally programmable shunts for hydrocephalus, which require adjustments to patient valve settings. Sources of magnetic field interference can be external (e.g. from a cell phone or MRI machine) or internal (from a cochlear implant, for example), according to the FDA in 2019.
Here are six things to know about shunts and magnetic field interference:
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Be aware of sources of external magnets.
Potential magnetic field interference can come from cordless drills, cell phones, electronic tablet devices, metal detectors and earbuds/headphones. In 2018, the FDA noted, “it is reasonable to assume that a shunt valve that is manipulated by a hand-held magnetic tool may also be vulnerable to other external magnetic sources (in the environment),” noting that more research is needed on the subject
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To date, FDA studies conclude that magnetic handheld devices are safe as long as they are kept at least two inches away from the shunt valve, although the agency notes that differences in body physiology and magnet characteristics may affect results. The FDA advises that hydrocephalus patients using earbuds or a cell phone should use these on the opposite ear from where the shunt is located.
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Take note of internal magnets.
Magnetic hearing devices (such as cochlear implants and bone conduction and middle ear hearing devices) may interact with shunts if the two are placed too close to each other. In this case, magnetic field interference could be avoided by putting the programmable CSF shunt valve on the contralateral side of a hearing device.
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A study of magnetic field strength of four bone conduction hearing devices and interaction with programmable shunt valves concluded it was safe to use the devices together but recommended at least a 5 mm distance in the case of one hearing device.
In addition, the FDA recommends checking shunt valve settings after placement or adjustment of other devices that contain magnets to ensure that the setting has not changed. For patients requiring bilateral hearing implants, the implanting physician should position the CSF shunt valve and the ipsilateral hearing implant at a maximum distance from one another to avoid issues with magnets and shunts for hydrocephalus, according to the FDA.
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Sometimes there are magnets you can’t avoid such as magnetic resonance imaging (MRI) and other imaging scans.
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MRIs may pose a risk to certain shunts’ valve settings. Before a patient has an MRI, they should tell the MRI technologist about any programmable shunts. Their doctor should arrange to have their shunt setting checked after the MRI, and reprogrammed if necessary.
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Unintended shunt valve changes can lead to serious issues.
Signs of shunt malfunction may include headache, lethargy, vomiting, vision changes and behavioral changes. Symptom severity depends on how much the setting changed, for how long and how sensitive the patient is to pressure changes. Overdrainage symptoms can include severe headache, nausea, vomiting and seizures and underdrainage may cause a recurrence of hydrocephalus symptoms.
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Parents and caregivers of children with magnetic CSF shunt systems should be told of possible interference, keep children away from magnets, encourage use of cell phones on the opposite side of the head from the shunt, know symptoms of magnetic interference and how to get help.
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Not all valves will be affected equally.
In three bench studies, Codman Certas® Plus programmable valves demonstrated no setting changes from common household magnets in over 2,200 exposures at close proximity (<5 mm). 1,2,3 * Watch a short video with details about the study here.
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Non-clinical testing demonstrated that the Certas valve is MR Conditional, meaning a patient with this device can be scanned safely, immediately after placement under specified conditions. Testing shows that the valve mechanism is resistant to unintended changes in the setting of a 3 Tesla MRI, although a clinician should confirm the valve setting after an MRI procedure.
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Any unintended CSF shunt valve changes should be reported
through the FDA MedWatch Program or the FDA Medical Product Safety Network (Med Sun) if your facility participates in the program.
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The agency advises including the following information with any report:
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- The suspected distance of programmable shunt from the magnetic source
- Identification of suspected magnetic source(s)
- Severity of patient symptoms
- Change in valve setting value from intended setting
- Manufacturer and brand of the CSF shunt or brand of hearing device
- Patient age, gender, underlying diagnosis for shunt
- Other medical devices in region of shunt (for example cochlear implant)
- Device evaluation post-explant, if available
δ Testing included 6 samples of each valve, tested 162 times per product at a distance of 4.3 mm on average.
* Benchtop studies are not necessarily indicative of clinical performance.
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Data on file. Jacobs Institute Engineering Solutions. Hydrocephalus Shunt Valve Assessment. February 5, 2019. Integra LifeSciences, Plainsboro, NJ, USA.
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Data on file. Jacobs Institute Engineering Solutions. Hydrocephalus Shunt Valve Assessment. Oct. 16, 2019. Integra LifeSciences, Plainsboro, NJ, USA.
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Data on file. Jacobs Institute Engineering Solutions. Magnetic Influence of CHPV, CERTAS, and Strata II Shunt Valves. September 16, 2021. Integra LifeSciences, Plainsboro, NJ, USA.