CASE PRESENTATION
We report the case of a 4-year-old boy who had received a simultaneous
bilateral cochlear implant (CI), because of a progressive profound
bilateral sensorineural congenital hearing loss of genetic origin. His
medical history is remarkable because, in January 2020, 1 year after CI
surgery, he developed a post-viral acute disseminated encephalomyelitis
(ADEM). At that time, the surgical removal of the magnet bilaterally was
done to confirm ADEM by brain and spine magnetic resonance imaging
(MRI); the magnets were replaced, uneventfully two months later.
Two years after CI, the boy incurred in a head trauma in the left
temporal region on the receiver–stimulator (R/S) area of the left CI,
which caused the dislodgment of the magnet and the rupture of the
silicone sheath of the magnet encasement.
Immediately after the trauma (October 2020), the left CI speech
processor could not be linked to the internal R/S. A CT scan excluded
fractures of the left temporal bone but identified the dislocation of
the magnet. (Figure 1) The CI team discussed with the parents the
options of explanting and re-implanting the left CI: however,
considering the correct position of the intracochlear array, the
previous normal intraoperative impedances and neural telemetry testing
and the very good speech perception performances, a conservative
surgical approach was considered mandatory. The risk of a subsequent
relapse of the magnet dislocation caused by the possible weakening or
even rupture of the thin silicone ring around the magnet well was
likely. The literature was not helpful in this respect: as far as we
know, no similar cases were reported in the literature, neither surgical
options different from explantation, were offered. PDLLA was identified
by our Maxillo-Facial Surgery consultant as a possible means to reduce
the risk of recurrent dislodgment. After thorough discussion and
informed consent by the parents, 2 weeks after the head trauma, the boy
underwent a surgical revision. A small skin incision over the R/S was
performed and 1 cm of the cortical bone around it for was expose.
(Figure 2) The dislodged magnet was replaced with a new sterile one, and
a tiny fissure of the silicon ring was observed. In order to reinforce
the damaged silicone case a PDLLA mesh was prepared: first it was heated
in hot water, then it was shaped in order to correctly cover the recess,
and finally it was screwed to the bone using 5 dedicated Sonic
Pins®, inserted in pre-drilled holes, by means of the
SonicWeld® system. The insertion was done with a
“sonotrode”, a dedicated ultrasonic tool that liquifies and expands
the pins after the insertion, allowing a tight bond with the mesh and
anchoring them securely to the holes in the bone. (Figure
2) No complications
were noticed immediately after the surgery. Figure 3 shows the surgical
site without inflammation, edema, hematoma, or infection at 1 month
after surgery; the area above the R/S was thickened but no coupling
troubles were reported at the time of CI reactivation. Immediate
restoration of optimal auditory performances at the pre-trauma levels
was achieved. At the latest check-up (18 months), no complications have
been observed, the CI is working regularly, and the child has no
complaint.