Mastoidectomy does not decrease the possibility that young patients will develop a middle ear infection

Performing a mastoidectomy, a group of operations on the temporal bone and middle ear to drain, expose, or remove an infectious, inflammatory, or neoplastic lesion, during cochlear implantation for young children does not decrease the possibility that the young patient will develop a middle ear infection. This is the conclusion of a new research study out of Israel.

Acute otitis media (AOM), or middle ear infection, has emerged as being a very common complication of cochlear implantation, especially in children under age two. An ear infection at first glance may appear to be a minor post-implantation complication, but the threat of otitis media is nevertheless very worrisome for the patients and their families. Their concern is that acute otitis media in implanted patients can be complicated by meningitis more often than in the non-implanted population.

One consequence of acute middle ear infection is mastoiditis, which occurs when the infection of the ear spreads from the ear to the mastoid bone of the skull (anatomically located directly behind the ear). The mastoid bone fills with infected materials and its honeycomb-like structure may deteriorate. Before the advent of antibiotics, mastoiditis was one of the leading causes of death in children. Now mastoiditis is a relatively uncommon complication of middle ear infection. However, past research has shown an increased incidence in mastoiditis among implanted children and adults who develop middle ear infections.

Some 350 patients have undergone cochlear implantation at a major Israeli treatment facility between 1989 and 2003. Pediatric implantations were carried out from 1993. Acute otitis media and mastoiditis complicated the post-operative course only in children. Specialists at the facility set out to determine the incidence of post-implantation acute infection of middle ear and mastoid only in pediatric patients.

This is the first investigation that evaluates the rate of acute otitis media in children implanted with different surgical approaches, one with and one without mastoidectomy. The authors of “Acute Otitis Media and Mastoiditis Following Cochlear Implantation: Comparison of Two Surgical Approaches,” are Lela Migirov MD, Arkadi Yakirevitch MD, and Jona Kronenberg MD, from the Department of Otolaryngology and Head and Neck Surgery, Sheba Medical Center (affiliated to the Sackler Faculty of Medicine), Tel Aviv University, Tel Aviv, Israel. Their findings are being presented at the American Academy of Otolaryngology-Head and Neck Surgery Foundation Annual Meeting & OTO EXPO, being held September 19-22, 2004, at the Jacob K. Javits Convention Center, New York City, NY.

Methodology:

A comparative retrospective study was conducted on all the children up to 16 years of age at the time of implantation who underwent cochlear implantation between 1993 and 2003 and were followed up for at least 18 months. The children were divided into two groups according to the surgical technique that had been used for the implantation: the Posterior tympanotomy approach (MPTA-with mastoidectomy) group and the Suprameatal approach (SMA-without mastoidectomy) group.

The SMA is based on the retroauricular tympanotomy technique. The middle ear is entered through the external auditory canal. The wide exposure of the promontory enables safe and easy performing of cochleostomy. The electrodes are passed into the cochleostomy through the closed suprameatal tunnel drilled within the temporal bone, postero-superior to the external auditory canal, posteriorly to the chorda tympani and lateral to the body of the incus. The selection of the SMA ran counter to the traditional MPTA cochlear implantation procedure, used primarily between 1993 until 1999.

The patients’ medical records were reviewed for age at the time of implantation, gender, a history of pre- and post-implantation acute otitis media, or mastoiditis, the surgical approach used, and history of adenoidectomy or insertion of ventilating tubes prior to implantation. The incidence of middle ear infection and mastoiditis before and after the implantation was compared between the two groups.

Results:

The study cohort consisted of 234 children, aged between 11 months and 16 years. Of these children, 116 (68 boys and 48 girls) underwent the implantation with the MPTA and the remaining 118 children (77 boys and 41 girls) were operated on with the SMA. The postoperative follow-up time was at least 18 months in both groups. Children in SMA group were significantly younger. Key findings include:

• Sixty-seven of the 234 (28.6 percent) study children had a history of acute otitis media prior to implantation. The subjects included children in which AOM was diagnosed from four weeks to 18 months after the implantation. There were no significant differences between the two groups in terms of AOM prior to implantation and AOM after surgery.
• A significant majority of the children with a history of pre-implantation AOM (22/29 in MPTA group, 26/38 in the SMA group) did not suffer from AOM post-implantation. In addition, an incidence of AOM after implantation in children who did not have history of AOM prior to the procedure was unrelated to surgical approach.
• Overall, 47 children (20.1 percent) had post implantation AOM compared to 67 children (28.6 percent) who had pre surgery middle ear infections.
• Eleven patients developed subperitosteal abscess after implantation. All 11 had been implanted with MPTA, and mastoiditis was diagnosed only on the implanted side in each case. Swelling behind the ear, and edema and ear protrusion were seen in all 11 children.
• Seven out of 11 children had no history of AOM prior to implantation. Three patients suffered from AOM a few months following mastoiditis, these children had no history of pre-implantation AOM or AOM before mastoiditis.

Conclusions:

Otitis media is the most common bacterial infection in children. Since cochlear implant (CI) patients include children less than two years of age, it is not surprising that AOM and mastoiditis represent common problems in the implanted population. The findings from this research reveal that children with pre-implantation history of AOM had higher risk of post implantation AOM than implanted healthy children. The rate of AOM decreased after the implantation, a finding that had previously been reported by others. However, more than a half of children who suffered from AOM post-CI had no history of AOM prior to implantation.

Eleven patients developed mastoiditis in their late post-implantation stage with four treated for an abscess beneath the membrane surrounding the bone. The possible explanation for development of mastoiditis and subperiosteal abscess in patients implanted with MPTA may be that the post-mastoidectomy cavity can collect a large amount of pus before clinical presentation.

Essentially, the researchers found that mastoidectomy in cochlear implantation surgery did not prevent the development of acute infection in the middle ear and mastoid. The incidence of post-implantation AOM generally decreased compared to pre implantation AOM, and this decrease was not related to whether or not the surgical approach for implantation included mastoidectomy. In our opinion, the decrease of incidence of acute middle ear infection in implanted children is the result of the natural course of otitis media.