In a July 16, 2019 letter addressed to medical-related specialists, including audiologists and ENT physicians, the US Food and Drug Administration (FDA) states its desire to increase awareness about potential complications in patients implanted with both programmable cerebrospinal fluid (CSF) shunt systems and some hearing implants that contain magnets, such as cochlear implants, bone-conduction hearing devices, or middle-ear hearing devices. It reports that magnetic interactions between these devices may occur when implanted in close proximity to each other, and these interactions may lead to unintended changes to the programmable CSF shunt valve settings.
Cerebrospinal Fluid (CSF) Shunt Systems are commonly used to treat hydrocephalus, a condition that can cause problems with physical and mental development. If untreated, it can be fatal. CSF shunt systems drain excess fluid from the brain to another part of the body where the fluid is absorbed.

According to the FDA, if magnetic interactions inadvertently change the programmable CSF shunt valve settings, then over- or under-drainage of CSF may occur. Patients may experience symptoms such as altered mental status, headaches, lethargy, irritability, vomiting, changes in vision, and difficulty walking. If left untreated, symptoms could progress to include loss of consciousness, seizures, hemorrhage, or even death.

Patients implanted with programmable CSF shunt systems may have a potential risk of experiencing an unintended change in their valve setting if exposed to strong magnetic fields. The FDA previously developed a website on the general topic of programmable CSF shunts which includes information about magnetic field interference with programmable CSF shunt valves and possible interactions with common magnetic sources (such as security screening systems, tablets, toys with magnets and cell phones).

The letter offers several recommendations for providers and patients:

  • Educate patients and caregivers about this potential risk and be sure they know when to have their programmable CSF shunt valve checked, what symptoms are associated with potential over- or under-drainage of CSF, and when to contact you.
  • Check the programmable CSF shunt valve setting after placement or adjustment of other devices that contain magnets to ensure that the setting has not changed. Only a trained clinician, such as a neurosurgeon, should check the shunt valve setting and adjust the setting, if necessary.
  • Consider the location of placement of the programmable CSF shunt valve if the patient has other implanted devices known to contain magnets in close proximity. For example:
    • Consider placing the programmable CSF shunt valve on the contralateral side of a cochlear implant or implantable bone conduction hearing device, if the patient’s anatomy and clinical picture permit such a strategy.
    • For patients requiring bilateral hearing implants, which use magnets and a programmable CSF shunt, the implanting physician should position the CSF shunt valve and the ipsilateral hearing implant at a maximum distance from one another.
  • Contact the applicable device manufacturer for further information.

The FDA is also asking patients, device manufacturers, and healthcare personnel to report all adverse events or suspected adverse events experienced with programmable CSF shunts and potential magnetic interference. The Agency will continue to keep the public informed if new or additional information becomes available.

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