Mariano Sturla MD, Presenter: Nothing to Disclose

Alejandro Gomez RT, Abstract Co-Author: Nothing to Disclose

Eduardo Galli MD, Abstract Co-Author: Nothing to Disclose

Natalia A. Hiriart MD, Abstract Co-Author: Nothing to Disclose

Show the usefulness and implications of electrode position detection in cochlear implant patients.

68 patients with cochlear implants were studied with CT after surgery and in the followup (5 years period). In all of them electrodes were placed in the Scala Tympani at surgery. We used a 4 row scanner Philips MX8000Quad. Scan parameters were 0.5mm thickness, 0.5 reconstruction index and 0.5 pitch. To determinate the exact position, we perform reconstructions(MPR, cMPR and 4D) and to determinate implant functionality we performed functional tests (voice perception, interpretation and discrimination) in all patients.

In 68 patients (75 implants) were imaged after surgery. 71 implants were followed up within a period of 5 years. Exact position of electrodes was identify in 97,1% (69/71). 2 implants (2,9%) were impossible to determinate due to strike artifact. We had two main types of migration; one occurs towards the tympanic box and the other inside the cochlea(scalar migration). 95,7% implants (66/69) were located at the Scala Tympani. All patients had normal functional tests for voice perception, interpretation and word discrimination. Only one showed at followup, abnormal tests and was proved to be a software calibration issue. In 4,3%(3 of 69) implants we discovered migration. In 2 of this 3 patients( 2,8% of total) the electrode was identified at Scala Vestibuli beyond de basal turn of the cochlea, confirmed by CT. No one had impaired hearing functional tests. The other patient showed electrode migration within the middle ear towards the tympanic cavity (1,5% of total),presenting abnormal tests.

Computed Tomography is a reliable method to determinate the electrode position and migration. Electrodes localization is a relevant information to the surgeon and must always be reported. This preliminary results sugest that the existence of middle ear migration is more associated with hearing loss than the scalar migration. Scalar migration is more frecuent beyond de basal turn of the cochlea. We beleave that a larger series of patients is needed to confirm this preliminary results.

Electrode position and location plays an important roll in the post-operative followup providing critical information to the surgeon.

Sturla, M, Gomez, A, Galli, E, Hiriart, N, Cochlear Implants: Electrode Migration and its Implications.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14001827.html