The magnets in some hearing implants may interfere with the operation of programmable cerebrospinal fluid (CSF) shunt systems used to treat hydrocephalus, causing over- or under-drainage, the FDA warned yesterday.

Magnetic interactions between cochlear implants, bone-conduction hearing devices or middle-ear hearing devices implanted too closely to shunt systems may “ lead to unintended changes to the programmable CSF shunt valve settings,” the agency said in a statement.

CSF shunt systems drain excess fluid from the brain to another part of the body where the fluid is absorbed. Patients who experience over- or under drainage of cerebrospinal fluid 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, the agency warned.

The FDA made the following recommendations to pediatricians, ear nose and throat physicians, neurosurgeons, neurologists, audiologists, urgent care physicians, emergency responders, nurses, and other health care providers present during shunt implant surgeries:

• • 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.
  • Contact the applicable device manufacturer for more information.

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.