Effect of magnetic resonance imaging on implantable eyelid weights.

Implanted upper eyelid gold weights are used to prevent corneal injury in patients with facial nerve paralysis. Some of these individuals require postoperative radiographic surveillance for recurrent lateral skull base disease. Magnetic resonance imaging (MRI) provides the most accurate radiologic assessment; however, there is concern about the safety of performing MRI in patients with any metallic implant. Potential risks include local tissue heating and implant migration. Gold weights of 0.8 and 1.4 g were placed in an open chamber and were exposed to a magnetic field of 1.5 T. There was no measurable motion or displacement of the weights. The results were similar in 6 rats in which gold weights were subcutaneously implanted. Additionally, histologic examination of the implant sites revealed no adverse tissue effects attributable to MRI-generated heating of the implants. When carbon steel implants in the rat model were subjected to the magnetic field, there was no displacement of the implants and no adverse tissue effects were noted, despite the fact that a carbon steel implant in an open chamber demonstrated significant migration. The absence of motion of the gold weight implants combined with the lack of adverse tissue effects suggests the relative safety of performing MRI in patients with previously placed gold weights as upper eyelid implants.