A PVP shunt is a surgically implanted device in a ventricle of the brain which can be fitted to patients of all ages as a treatment for hydrocephalus to drain excess CSF from the brain to another part of the body. PVP shunts have a magnetic valve placed under the skin on or near the mastoid bone to allow the shunt to be adjusted by an external control magnet if required. However, the magnetic valve is also susceptible to other external magnetic fields, such as those emitted by many earphones, including TDH and DD series earphones (if positioned over the site of the shunt). If activated inadvertently by an external magnetic field the shunt can malfunction, cause a change in intracranial pressure and lead to a potentially life-threatening situation.
The BSA electrophysiology special interest group have written a position statement due to be published later this year on the safe practice when testing patients with a PVP shunt, but in the interim would like to offer the following advice;
All patients, parents or carers must be asked if the patient has a shunt.
Do NOT place the following transducers on or near the ear with a PVP shunt valve;
Ear inserts can be used, but a cautious approach is recommended by keeping the transducer part at least 5 cm from the mastoid containing the shunt valve at all times.
Bone conduction testing can be performed on the ear contralateral to the PVP shunt valve. For adult pure tone audiometry the bone conductor can be placed on the forehead, as long as this is 5cm from the mastoid with the PVP shunt and correction factors applied as defined in BS EN ISO 389-3, Table C.1.
Before considering hearing aid fitting seek shunt manufacturers advice regarding the safe level of the PVP shunt and the magnetic field strengths emitted by hearing aid from the hearing aid company, with particular attention to hearing aid ancillary equipment.
Public Health England has recently posted new advice that babies with a PVP shunt should not undergo hearing screening but should be referred to Audiology services for hearing assessment. (https://phescreening.blog.gov.uk/2019/07/19/listening-to-the-needs-of-local-newborn-hearing-screening-providers/