Ultrasound in Diagnosis of Magnet Dislocation of Cochlear Implants: A Retrospective Study in Patients With Surgical Magnet Repositioning and Preinterventional Ultrasound Examination.

OBJECTIVE

To investigate whether ultrasound is a reliable diagnostic tool to identify magnet dislocation in patients with cochlear implant.

DESIGN

Retrospective analysis.

SETTING

A tertiary referral medical center.

PATIENTS

Patients with cochlear implant who presented with the suspicion of magnet dislocation between January 1, 2009 and July 31, 2019.

INTERVENTIONS

Preinterventional ultrasound with subsequent surgical magnet repositioning.

MAIN OUTCOME MEASURES

Accuracy of ultrasound in detecting magnet dislocation; intraoperative extent of magnet dislocation.

RESULTS

Out of the 28 included patients (n = 28 magnets, 36% ♀; 51.6 years [±19.0 yr]) the diagnosis by the preoperative ultrasound was confirmed intraoperatively in 25 patients (89%). In two cases (7%), tissue swelling impeded the determination of the magnet by the preoperative ultrasound. In one case, ultrasound misdiagnosed the magnet as not dislocated. During revision surgery, all 28 magnets were repositioned successfully revealing a predominant partial dislocation (86%) compared with complete magnet dislocation (14%).

CONCLUSION

In CI-patients undergoing 1.5 Tesla MRI, partial magnet dislocation occurs much more frequently than complete magnet dislocation. The clinical suspicion of a dislocated cochlear implant magnet can be accurately confirmed by preoperative ultrasound. Thus, preoperative diagnostic ultrasound can be advocated as the diagnostic tool of first choice.