The US Food and Drug Administration (FDA) has issued a statement warning healthcare providers about potential complications in patients fitted with both programmable cerebrospinal fluid (CSF) shunt systems and certain magnetic hearing devices.

In an open letter to healthcare providers issued on 16 July, the agency warned that magnetic interactions between the devices may occur when they are implanted within close proximity to each other, leading to unintended changes to the CSF shunt valve settings. This could occur in patients fitted with cochlear implants, bone conduction hearing devices or middle ear hearing devices, the agency said.

CSF shunt systems are commonly used to treat hydrocephalus, swelling of the brain due to excess build-up of cerebrospinal fluid. The shunt is supposed to redirect the excess fluid to the abdomen or the heart where it can be absorbed, but if magnetic interactions inadvertently change the CSF shunt settings, then over- or under-drainage of CSF may occur.

If this happens, patients may experience symptoms such as altered mental state, headache, lethargy, vomiting, visual changes and difficulty walking. Untreated, this may progress to loss of consciousness, seizures, haemorrhage or even death.

The FDA has recommended that caregivers educate patients about this potential risk to ensure they know when to have their CDF shunt checked, and what dangerous symptoms to look out for.

The agency has also advised clinicians to 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.

It recommends that healthcare providers attempt to place programmable CSF shunt valves on the opposite site of the head to a patient’s magnetic implanted hearing device. For patients with bilateral magnetic hearing implants and a CSF shunt, physicians are advised to position the shunt and the hearing implants as far away from each other as possible.