Pediatric Cochlear Implantation

Introduction

The cochlear implant (CI) is unique among medical devices in that it serves as a neurosensory prosthesis capable of restoring or providing de novo the sense of hearing to its users. As technology advances with hardware, sound processing algorithms, and mapping strategies, CI users have achieved ever more impressive outcomes in both hearing and speech development. Many children born with severe to profound hearing loss today will go on to participate in mainstream curricula with the help of CIs. The US food and drug administration (FDA) has approved the use of CIs in children at least 1 year of age, and in certain cases, surgeons will implant children off-label at substantially younger ages. With careful patient selection, attention to surgical technique, and comprehensive postoperative rehabilitation, the CI is an extremely viable option for restoring hearing in children with severe to profound hearing loss.

Key Operative Learning Points

• Careful patient selection is the key to achieving optimal hearing and speech outcomes

• Use of intraoperative facial nerve monitoring is recommended

• Review of imaging prior to surgery is critical to anticipate anatomic variants, such as:

  • High-riding jugular bulb

  • Low-hanging dura

  • Narrow facial recess width

  • Bifid or dehiscent facial nerve

  • Stenotic round window niche

  • Cochleo-vestibular abnormalities, including enlarged vestibular aqueduct

• Be sure to calculate an appropriate weight-based volume of local anesthetic prior to injection. In very young children, the maximum allowable volume is often less than 10 cc of 1% lidocaine.

• To increase symmetry for bilateral simultaneous implantation, use metal templates to determine optimal location for incisions and for subperiosteal pocket development.

• Hemostasis at each step is critical, especially in very young children. Allow adequate time for vasoconstrictor effect, have bipolar cautery available (especially for the second side on bilateral surgery), use bone wax for unpneumatized diploic bone during mastoidectomy.

• Fixation can be achieved with a traditional well, with stay sutures, or with a tight subperiosteal pocket. Be prepared to use any of the above options if needed to ensure the secure positioning of the receiver stimulator.

• Device manufacturer and electrode choice will depend upon patient preference, anatomic considerations, and surgeon/implant program experience and routine. Be familiar with the device electrode to be implanted as there are subtle but critically significant differences among them.

• Soft surgery techniques can optimize outcomes not only by preserving residual hearing, but by preserving spiral ganglion neurons. These may include:

  • Use of systemic and/or topical steroids intraoperatively

  • Use a slow drill speed when drilling on the otic capsule

  • Slow electrode insertion to minimize intracochlear pressure during insertion

  • Choice of anterioinferior cochleostomy site confluent with round window or use of the round window approach to ensure scala tympani insertion

• Plugging of the cochleostomy (if performed) is usually accomplished with temporalis fascia or muscle. In bilateral simultaneous cases, harvest enough tissue for both cochleostomies from the first side to eliminate a second step and reduce the potential for bleeding from the contralateral side, particularly when electrocautery can no longer be used.

• Layered closure using absorbable suture.

• A tight mastoid dressing should be left in place for 48 hours. This can be replaced with a Glasscock dressing by the family, to be used during sleep for comfort, or if the child is manipulating the incision.

• Activation is typically performed 3 to 4 weeks postoperatively.

Preoperative Period

Extensive preparation is necessary prior to embarking upon CI in a child. It is critical to use a multidisciplinary approach for patient selection and preparation of the family and patient for surgery. While the surgery itself takes only a few hours, successful CI use requires months to years of intense therapy, continued device maintenance, and enrollment in an appropriate academic setting that will support the development of speech and language using electronic hearing. Patients should be evaluated by a CI program with experience implanting and habilitating children with hearing loss. Evaluation by Otolaryngology, Audiology, and Speech and Language Pathology are essential to determine candidacy for implantation. Collaboration with other specialties including genetics, social work, developmental pediatrics, neurology, and neuropsychology can help to predict postoperative rehabilitation challenges and set appropriate expectations for performance.

For children with congenital deafness, better speech and hearing outcomes are correlated with earlier age at implantation. The FDA has approved cochlear implantation for children with bilateral severe-to-profound cochlear implantation at 1 year of age or older. Off-label implantation at a younger age is frequently considered, particularly in conditions such as post-meningitic hearing loss, where progressive labyrinthitis ossificans can obliterate the cochlear duct, preventing successful electrode insertion. Children as young as 3 months of age have been successfully implanted.

It is difficult to overstress the importance of establishing a relationship between the family and the entire implant team. Educating families regarding the implant process, especially with regard to the necessary postoperative therapy required for successful use of the device, is critical in preventing implant failure in the form of non-use. While CI technology is certainly one of the more miraculous developments in modern medicine, it is by no means a cure-all, and success requires much more than good surgical technique. Partnering with families in advance to reach this understanding will make the habilitation process a much more positive experience for all parties involved. For families with a language barrier, limited socioeconomic support, or other comorbid medical conditions requiring frequent appointments, the process is often felt to be overwhelming. It can be helpful to involve social work to facilitate transportation, parking, and coordination of multiple appointments. Often, helpful insight can be obtained from teachers, audiologists, and speech pathologists from the child’s school, early childhood program, or early intervention service. Obtaining releases from the parents so providers can discuss cases with these individuals can lead to greater understanding of the needs of the patients and their families. Often creative solutions to problems can be reached in this manner.

Many cases require complex decision making regarding whether the patient will experience overall benefit from a CI. In pre-lingually deafened individuals, neural plasticity decreases over time, limiting the potential benefit of CIs in a time-dependent manner. Still, every case varies and any given child can have results, which exceed expectations. This is an especially important conversation to have with pre-lingually deafened teenagers who come seeking CIs. It is most important to ask what the patient’s expectations are in this situation; that is, why do they want an implant? Sound awareness for safety and speech pattern perception to augment and support lip-reading are reasonable expectations in such cases, whereas use of the telephone and development of typical speech are unreasonable expectations.