Background: Exposure to magnetic fields may alter the settings of programmable ventriculoperitoneal shunt valves or even cause permanent damages to these devices. There is little information about this topic, none on live patients.
Objective: To investigate the effects of 1.5-tesla magnetic resonance imaging (MRI) on Hakim-Codman (HC) pressure programmable valves implanted in our hospital.
Methods: A single-center prospective study to assess the rate of perturbations of HC programmable valve implanted. One hundred consecutive patients implanted for different clinical reasons between 2008 and 2012 were examined. A conventional skull x-ray before and after a standard MRI on 1.5 tesla. We evaluated before and after results, analyzed modification rate, and verified eventual damages to the implanted devices.
Results: Implanted HC valves are extremely handy and durable, even if they are likely to change often due to the exposure to magnetic fields. None of the patients complained of heating effects. Oscillations range from 10-30 mm H2O with a patient who reached 50 mm H2O and 1 who reached 60 mm H2O. Global alteration rate was 40%: 10 patients (10%) experienced a 10 mm H2O change; 14 patients (14%) had a 20 mm H2O change; 6 patients (6%) had a 30 mm H2O change; 8 patients (8%) had a 40 mm H2O change; 1 patient had a 50 mm H2O change; and 1 patient had a 60 mm H2O change.
Conclusions: HC valves presented a variable perturbation rate, with an alteration rate of 40% with 1.5-telsa MRI. We have not observed malfunctioning hardware as a result of magnetic influence. We claim a cranial x-ray immediately after the MRI because of a high risk (40%) of decalibration, especially in patients with low ventricles compliance.
Keywords: Hakim-Codman programmable valve; Hydrocephalus; Implantable valves; Magnetic field exposure; Shunt susceptibility.
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