Background
Sedation or anesthesia is often necessary in pediatrics when magnetic resonance imaging is performed. This anesthesia outside of the operation room combines specific requirements and risks. Ferromagnetic foreign bodies are a clear contraindication for magnetic resonance imaging due to the high magnetic field within the scanner. However, insertion of various small objects in mouth, nose or external auditory is not uncommon in small children and often remains unnoticed until specific symptoms develop. Early warning sings like movement of the object or heat development are then concealed by sedation or anesthesia preventing a timely termination of the possibly hazardous procedure.

Case presentation
We present a case of a three year old Caucasian with an acute sinusitis due to unknown ferromagnetic foreign body in his nasal cavity. As soon as the suspicion was raised the procedure was aborted and the object that revealed to be a small button battery was successfully removed.

Conclusions
The potential of unwelcome side effects and effective safety strategies of magnetic resonance imaging are discussed as well as the complications arising from ingested batteries.