Programmable Shunt Valves: In Vitro Assessment of Safety of the Magnetic Field Generated by a Portable Game Machine

Abstract

Cerebrospinal fluid (CSF) shunts are frequently used to treat hydrocephalus. The use of a programmable shunt valve allows physicians to easily change the opening pressure. Since patients with adjustable CSF shunt valves may use portable game machines, the permanent magnets in these machines may alter the shunt valve programmed settings or permanently damage the device. This study investigated the risk of unintentional valve adjustment associated with the use of game machines in patients with programmable CSF shunt valves. Four adjustable valves from 4 different manufacturers, Sophysa Polaris model SPV (Polaris valve), Miethke proGAV (proGAV), Codman Hakim programmable valve (CHPV), and Strata II small valve (Strata valve), were evaluated. Magnetic field interactions were determined using the portable game machine, Nintendo DS Lite (DS). The maximum distance between the valve and the DS that affected the valve pressure setting was measured by x-ray cinematography. The Polaris valve and proGAV were immune to unintentional reprogramming by the DS. However, the settings of the CHPV and Strata valves were randomly altered by the DS. Patients with an implanted shunt valve should be made aware of the risks posed by the magnetic fields associated with portable game machines and commonly used home electronics.

Effect of Amusement Park Rides on Programmable Shunt Valve Settings

“…Environmental magnetic fields such as those imparted by magnetic resonance imaging, household toys, and electronics are capable of altering settings of magnetically programmable shunt valves [1,2,3,4]. We show here, for the first time, that changes in magnetically programmable shunt valve settings in 2 different valve types are possible after exposure to amusement park rides with elevated vertical G forces, irrespective of the presence of LIMs or magnetic brakes.…”

“…As a result, these valves are susceptible to magnetic forces such as those encountered with magnetic resonance imaging and, to a lesser extent, magnetic forces from objects in the environment such as magnetic toys and electronics [1,2,3,4]. Magnets associated with newer rollercoaster rides include linear induction motors (LIMs) and magnetic brakes, and it is unknown whether the associated magnetic force is capable of changing the shunt valve settings of a passenger on a rollercoaster.…”

Initial experience with the Codman Certas adjustable valve in the management of patients with hydrocephalus

“…The Codman Hakim programmable valve (CHPV) has been described in many studies [3,5,6]. The adjustment system is not portable and accidental readjustments have occurred with exposure to MRI procedures and with exposure to magnetic toys [10,11]. The Strata valve is very similar to the Certas TM valve in design and includes a portable adjustment system quite similar to the TMS.…”

“…The Strata valve is very similar to the Certas TM valve in design and includes a portable adjustment system quite similar to the TMS. It has also been reported to accidently change settings with exposure to both MRI and magnetic toys [11]. The Sophysa Polaris valve includes a portable adjustment system with a compass tool to indicate correct positioning of indicator tool over the valve [12].…”

Radiation Risk Due to Shunted Hydrocephalus and the Role of MR Imaging–Safe Programmable Valves

“…In addition, external magnetic fields found in devices such as video game systems, children's toys, cell phones, kitchen appliances, loud speakers, iPads (Apple, Cupertino, California), and so forth have been shown to cause valve malfunctions in shunts. [33][34][35][36][37][38] This exposure not only contributes to the inability of the shunt device to work properly but leads to increased hospital visits and thus increased diagnostic scans from CT and x-rays. There have been specific instances of these cases: A boy playing with toy magnets altered the valve settings on his shunt, 38 a man with a programmable shunt attempted suicide by using an electromagnet, 39 an iPad 2 altered the setting on the valve of a 4-month-old girl, 37 and the shunt setting of a 5-year-old boy was changed by a household electric appliance.…”