People with implanted nerve stimulators to treat brain, spinal or other disorders may risk comas, serious injury or death if they undergo magnetic resonance imaging scans, U.S. regulators warned on Tuesday.

The Food and Drug Administration said it had received several reports of serious injuries, including comas and permanent neurological impairment, in patients with the stimulators who underwent MRIs.

The reports involved patients with deep-brain or vagus nerve stimulators, but similar injuries could occur with any type of implanted neurological stimulator, the FDA said in an advisory posted on the agency’s Web site.

Deep brain stimulators are used as therapy for Parkinson’s disease, and vagus nerve stimulators treat epilepsy.

The problems likely occur because electrodes attached to wires can be heated and damage nearby tissue, the FDA said.

MRI scans are used to diagnose a variety of health problems.

Patients with implanted stimulators should consult their physician before having an MRI to find out if the test can be performed safely, the FDA said. In some cases, other imaging options will need to be used.

Radiologists should make sure patients are screened for implanted devices, including ones that have been turned off or removed. Some wires stay in the body after device removal, and they could become heated, the FDA said.