MRI-induced artifact by a cochlear implant with a novel magnet system: an experimental cadaver study.

PURPOSES: To primarily evaluate MRI-induced effects for Ultra 3D cochlear implantation in human cadavers in terms of artifact generation and MR image quality. METHODS: Three human cadaveric heads were submitted to imaging after unilateral and bilateral cochlear implantation. The 1.5 T MR examination protocol was chosen in accordance with our institutional protocol for the assessment of brain pathology. The maximal signal void size was measured according to each sequence and plane. Two experienced neuro-radiologists and one experienced otoneurosurgeon independently evaluated the MR image quality findings. A 4-point scale was used to describe the diagnostic usefulness of 14 brain structures. RESULTS: Shape and size of the artifacts were found to be highly related to MRI sequences and acquisition planes. MRI sequences and processing algorithms affected the ability to assess anatomical visibility. Image quality appeared either high or assessable for diagnostic purposes in 9 out of 14 of the ipsilateral structures, in at least one plane. Anatomical structures contralateral to the cochlear implant were highly visible in all conditions. Artifact intrusion clearly improved after application of metal artifact-reduction techniques. In the case of bilateral cochlear implant, a mutual interaction between the two implant magnets produced an additional artifact. CONCLUSIONS: We performed the first cadaver study aimed at systematically evaluating the MRI-induced artifacts produced by a cochlear implant with a novel four bar magnet system. Specific brain structures can be assessable for diagnostic purposes under 1.5 T MRI, with the cochlear implant magnet in place.

The usefulness of the O-MAR algorithm in MRI skull base assessment to manage cochlear implant-related artifacts.

Objective: To assess artifact size and MRI visibility when applying the "Orthopedic-Metal Artifact Reduction" (O-MAR) algorithm for cochlear implant (CI) scanning. Methods: Two volunteers were submitted to 1.5 T MRI with an Ultra 3D CI receiver stimulator placed on their head. Four angular CI orientations were adopted: 90, 120, 135 and 160 degrees. Volunteers were scanned in each condition using T1w and T2w TSE sequences, as well as O-MAR sequences, in both axial and coronal planes. Quantitative comparisons were made of signal void and penumbra extent. Additionally, qualitative evaluations of global image quality, MRI readability with respect to 12 anatomical structures and visibility through the penumbra were undertaken. Results: After application of the O-MAR protocol, the radius of the signal void reduced from 50.76 mm to 45.43 mm and from 49.22 mm to 40.15 mm on T1w and T2w TSE axial sequences, respectively (p < 0.05). Qualitatively, sequences acquired with O-MAR produced better outcomes in terms of image quality and anatomical depiction. Despite the area of the penumbra being increased for the O-MAR protocol, visibility through penumbra was improved. Conclusions: Application of O-MAR may provide a complementary strategy to those already in use to obtain diagnostically useful MRI examinations in the presence of a CI, especially in case of skull base diseases requiring MRI monitoring.

Extrusion and Dislocation in Titanium Middle Ear Prostheses: A Literature Review.

Titanium middle ear (ME) prostheses are widely used in surgical practice due to their acoustic properties. However, they present a significant drawback shared by all synthetic materials currently in use for ME reconstruction: they can be rejected by the organism of the host. In this study, we aim to review the current literature on titanium partial ossicular replacement prostheses (PORPs) and total ossicular replacement prostheses (TORPs) extrusion and dislocation. Eighty articles were analysed after a full article review based on the inclusion and exclusion criteria. The most common indication for reconstruction was chronic otitis media with cholesteatoma. The average extrusion or dislocation rate was 5.2%, ranging from 0 to 35%. The average improvements in the air-bone gap were 12.1 dB (1.6 dB to 25.1 dB) and 13.8 (-0.5 dB to 22.7 dB) for the PORP and TORP groups, respectively. The data reported on this topic are highly variable, demonstrating that functional outcomes are difficult to predict in clinical practice. We believe that the current limitations could be overcome with technological developments, including bioengineering research focused on promoting prosthesis adaptation to the ME environment.

Titanium Biohybrid Middle Ear Prostheses: A Preliminary In Vitro Study.

Ossiculoplasty is a surgical operation performed to restore auditory transmission through the reconstruction of the ossicular chain using prosthetics. Tissue bioengineering has assumed a pivotal role in implementing alternatives to conventional ossicular middle ear replacement prostheses, to overcome extrusion while preserving acoustic properties. This in vitro study aims to explore, for the first time in current literature, the feasibility of a biohybrid middle ear prosthesis, composed of titanium surrounded by a bone extracellular matrix as bio-coating. We have hereby studied the adhesion and proliferation of human adipose-derived mesenchymal stem cells (hASC) on titanium scaffolds in vitro. Moreover, we identified the osteogenic differentiation of hASC using an immunofluorescence assay to analyze osteoblasts' gene expression profiles (Alp, Runx2, Col1a1, Osx, and Bglap), and we counted the presence of collagen as a marker of hASC's ability to secrete an extracellular matrix. We utilized scanning electron microscopy to evaluate the presence of an extracellular matrix on the scaffolds. Our preliminary data demonstrated the titanium's ability to support human adipose-derived mesenchymal stem cell colonization, proliferation, and osteoblastic differentiation, in order to obtain a biohybrid device. Our experience seems encouraging; thus, we advocate for further in vivo research to corroborate our results regarding bone transplantation.

Current trends on subtotal petrosectomy with cochlear implantation in recalcitrant chronic middle ear disorders.

Objective: To establish the safety and effectiveness of subtotal petrosectomy with cochlear implantation in patients affected by chronic middle ear disorders to refractory to previous surgical treatments. Methods: A multicentre, retrospective study was conducted on patients affected by recalcitrant chronic middle ear disorders who underwent cochlear implantation in combination with subtotal petrosectomy. Patients' details were collected from databases of 11 Italian tertiary referral centres. Additionally, a review of the most updated literature was carried out. Results: 55 patients were included with a mean follow-up time of 44 months. Cholesteatoma was the most common middle ear recurrent pathology and 50.9% of patients had an open cavity. 80% of patients underwent a single stage surgery. One case of explantation for device failure was reported among the 7 patients with post-operative complications. Conclusions: Subtotal petrosectomy with cochlear implantation is a benchmark for management of patients with recalcitrant chronic middle ear disorders. A single stage procedure is the most recommended strategy. Optimal follow-up is still debated. Further studies are required to investigate the role of this surgery in paediatric patients.

"Emergency" Cochlear Implantation in Labyrinthitis Ossificans Secondary to Polyarteritis Nodosa: How to Face a Rare Entity.

Polyarteritis nodosa (PAN) is a systemic vasculitis affecting the small- and medium-sized arteries that may present with hearing impairment. In rare cases, PAN may be associated with progressive labyrinthitis ossificans (LO), an otologic emergency requiring early cochlear implantation (CI) to restore hearing before the complete, irreversible cochlear ossification. We report the first case in the literature of a patient affected by PAN with bilateral sudden sensorineural hearing loss and rapid LO who underwent "emergency" bilateral simultaneous CI. This case report emphasizes the importance of an early audiological evaluation in patients with PAN when LO is suspected. Multidisciplinary approach is mandatory when facing organ-specific manifestations in patients with PAN. Detailed discussion is provided with particular regard to clinical and radiological presentation as well as CI outcomes in such a rare and challenging case.