Cochlear implant infections

INTRODUCTION — Cochlear implants are medical devices that electronically stimulate the auditory nerve in the cochlea (inner ear), allowing people with severe to profound hearing loss to perceive sound.

Infection is the most common serious complication of cochlear implants. Forms of infection associated with cochlear implants include surgical site infection and otitis media; complications of otitis media include meningitis and mastoiditis.

A policy statement on surgical site infections and the prevention and treatment of acute otitis media and meningitis in children with cochlear implants was published in 2010 by the American Academy of Pediatrics [1]. Our recommendations are generally in keeping with this statement.

The pathogenesis, clinical presentation, microbiology, diagnosis, prevention, and treatment of cochlear implant infections will be reviewed here. General information about cochlear implants is discussed separately. (See "Hearing loss in children: Treatment", section on 'Cochlear implants' and "Hearing amplification in adults", section on 'Cochlear implants'.)

HARDWARE COMPONENTS — A cochlear implant consists of an internal device (implanted surgically) and external components (applied postoperatively) (figure 1).

The external device is the "sound processor"; it includes microphones that convert sound into electrical signals, a signal processor that filters and arranges the electrical signals, and a transmitter coil that sends processed signals and power across the scalp to a matching coil in the internal "receiver-stimulator."

The internal receiver-stimulator processes the signals it receives and passes them through an array of electrodes in the cochlea, where electrical activity stimulates auditory nerves based on electrode location in the cochlea, with higher frequencies in the base and lower frequencies toward the apex.

The internal and external devices contain magnets, which align the coils for efficient electrical induction. For patients with an older internal magnet, magnetic resonance imaging (MRI) may be contraindicated or require special preparation. For patients with a newer cochlear implant model, MRI may be performed without special preparation. Most implanted devices have magnets that are surgically removable, which reduces the metal artifact on MRI.

Issues related to perioperative antibiotic prophylaxis are discussed below. (See 'Perioperative antibiotic prophylaxis' below.)

FORMS OF INFECTION — Forms of infection associated with cochlear implants include surgical site infection (superficial wound infection versus deep infection involving the implanted device) and otitis media; complications of otitis media include meningitis and mastoiditis. Surgical site infections are more common in adults, while otitis media, meningitis, and mastoiditis are more common in children [2].

The general incidence of infection following cochlear implant placement ranges from 1.4 to 11.2 percent [3-6]. In one retrospective study including five state databases, the incidence of infectious complications following cochlear implantation was 8.2 per 1000 person-years in children and 5.2 per 1000 person-years in adults [5]. The higher rate of complications in children was attributed to repeat infections within 180 days of implantation.

Surgical infection: Superficial versus deep — Forms of surgical site infection include superficial wound infection and deep infection involving the implanted device.  

Epidemiology — Rates of surgical site infection have declined with use of smaller incisions and advances in surgical technique and skin flap design [3,6,7]. In one series including 462 adults and 271 children who underwent cochlear implantation between 1993 and 2002, the overall incidence of postoperative infection was 4.1 percent; deep infections occurred in 3 percent of cases, most of which required surgical intervention [3].

Microbiology — Most surgical site infections (superficial as well as deep) are caused by skin flora, specifically Staphylococcus aureus [3,4,8]. Other reported pathogens include coagulase-negative staphylococci, streptococci, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Achromobacter xylosoxidans, and Candida albicans.

S. aureus infection in the setting of foreign material, such as a cochlear implant, can be difficult to eradicate due to the formation of biofilm. S. aureus adheres to foreign material and produces exopolysaccharides (also known as glycocalyx); eventually, the organisms encased in glycocalyx coalesce to form biofilm [9,10]. Biofilms are complex bacterial communities with intraspecies communication and adaptation through quorum-sensing, which regulates both virulence and biofilm formation [11]. Bacteria near the surface of the biofilm are usually metabolically active, with access to surface nutrients; bacteria deep within the biofilm are metabolically inactive or in various stages of dormancy, so they are protected from host phagocytes and antimicrobial penetration. Approaches for specimen collection to optimize culture yield in the context of biofilm are discussed elsewhere. (See "Prosthetic joint infection: Epidemiology, microbiology, clinical manifestations, and diagnosis", section on 'Biofilm' and 'Obtaining specimens for culture' below.)

The presence of a foreign body reduces the S. aureus minimal inoculum required to cause infection by a factor of more than 100,000 to as little as 100 colony-forming units [12]. At least two factors increase this risk: (1) foreign bodies do not have a microcirculation, which is crucial for host defense and antibiotic delivery, and (2) the interaction between neutrophils and the foreign body can induce a neutrophil defect that may enhance susceptibility to infection [12,13].

Clinical manifestations — Patients who have undergone cochlear implantation and present with signs or symptoms suggesting infection warrant careful assessment to distinguish between superficial surgical site infection and deep infection of the implanted device.

Superficial surgical site infection typically occurs relatively early in the postoperative period; in one study including 653 adults with cochlear implant infection, the median time to presentation of superficial infection was 68 days (range 28 to 317 days). Findings may include fever, pain, erythema, swelling, and granulation tissue around the electrode array. Many cases present indolently, with pain around the receiver-stimulator in the absence of clinical evidence of inflammation. Some cases may be detected on routine evaluation with findings of painless swelling or crusting at the incision. Some patients with superficial infection require progressively stronger processor magnets, which may lead to development of a pressure ulcer; this finding may also develop if the processor is worn continuously (eg, not removed for sleep).

Deep (implant) infections typically occur in the first few months following placement; however, some manifest years later [8,14]. In one review of cochlear implantation surgeries among 653 Danish adults, major complications occurred in 11 patients (2 percent); of these, 6 occurred within the first 7 months postoperatively, 4 occurred approximately 2 to 3 years postoperatively, and 1 occurred 11 years later [14]. Findings of implant infection may include manifestations of surgical site infection as well as incisional drainage and/or wound dehiscence with implant exposure.

Diagnostic evaluation

General approach — The diagnostic evaluation for patients presenting with clinical manifestations of surgical site infection includes computed tomography (CT) of the head and temporal bone. In addition, for patients with incisional drainage and/or wound dehiscence with implant exposure, material from the site should be sent for culture. (See 'Radiographic imaging' below and 'Obtaining specimens for culture' below.)

Laboratory findings such as white blood count, erythrocyte sedimentation rate, and C-reactive protein are usually normal, so they do not help establish presence or absence of infection or guide treatment decisions.

Radiographic imaging — Routine CT of the head and temporal bone is warranted to evaluate for evidence of implant infection and/or identify other complications; findings of implant infection may include presence of fluid collection(s) or bony sequestration(s). For patients with suspected implant infection in the absence of localizing findings on CT imaging, gallium single-photon emission CT may be pursued [15].

Magnetic resonance imaging (MRI) is of minimal value for routine evaluation of patients who have undergone cochlear implantation, due to artifacts from the magnet and other metal in the receiver-stimulator. If MRI is absolutely necessary (eg, to evaluate for central nervous system involvement), the magnet can be removed and replaced with a titanium spacer (in most models) or the cochlear implant can be removed entirely (in older models or in case of refractory infection).

Obtaining specimens for culture — For patients with incisional drainage and/or wound dehiscence with device exposure, material from the site should be sent for culture. For patients without drainage who present with fluctuant fluid over the receiver-stimulator, the fluid may be aspirated; however, care must be taken to avoid injuring the device or introducing pathogens.

For patients with deep infection who undergo debridement, additional samples (including material debrided from the mastoid cavity, and receiver stimulator, if exposed) should be sent for culture. To optimize yield, cultures should be obtained directly from the implant surface, or if possible, sonicated from a removed portion of the device (such as a cochlear implant magnet) [8].

Molecular tests (eg, microbial gene sequencing) may be helpful when standard cultures are negative but clinical suspicion for infection is high or when specimens are obtained after antibiotic therapy has been initiated [8]. However, such findings must be interpreted carefully; molecular testing of material from nonsterile sites may reflect colonizing organisms rather than true pathogens causing significant infection.

Samples obtained from the external auditory canal are not useful for establishing a microbiologic diagnosis, given the presence of normal flora at this site.

Management

Superficial infection — Management of superficial surgical site infection consists of local wound care, oral antibiotic therapy with activity against methicillin-resistant S. aureus (MRSA), and close monitoring. Patients with persistent or progressive symptoms warrant further evaluation for deep infection. (See 'Deep (implant) infection' below.)

Appropriate regimens are summarized in the tables (table 1 and table 2 and table 3). The duration of therapy is 10 to 14 days. Additional issues related to antibiotic agents for treatment of skin and soft tissue infections due to MRSA are discussed further separately. (See "Methicillin-resistant Staphylococcus aureus (MRSA) in adults: Treatment of skin and soft tissue infections" and "Skin and soft tissue infections in children >28 days: Evaluation and management", section on 'Management approach'.)

Deep (implant) infection — Management of patients with suspected implant infection consists of culture of drainage material (if present), administration of empiric intravenous antibiotic therapy with activity against MRSA, surgical debridement (with collection of deep specimens for culture), and consideration regarding device removal [2].

●Empiric antibiotic therapy – Empiric antibiotic therapy consists of vancomycin; dosing is summarized in the tables (table 4 and table 5). Antibiotic therapy should be tailored to culture and sensitivity data when available. Patients with MRSA or Staphylococcus epidermidis should continue vancomycin; patients with methicillin-susceptible S. aureus (MSSA) should complete treatment with nafcillin (adults: 2 g intravenously [IV] every 4 hours; children: 150 to 200 mg/kg/day in 4 to 6 divided doses; max dose 12 g), oxacillin (same dosing as nafcillin) or cefazolin (adults: 2g IV every 8 hours; children: 100 to 150 mg/kg/day in 3 divided doses; max dose 12 g). In addition, for patients with S. aureus infection (MRSA or MSSA) and a retained device, we include adjunctive rifampin (adults: 300 to 450 mg orally twice daily; children: 10 to 20 mg/kg/day in 2 divided doses; max 600 mg/dose).

●Surgical debridement – The optimal scope of surgical debridement is uncertain. Some surgeons favor removal of all granulation tissue from the mastoid and middle ear, as well as debridement around the cochleostomy [16,17]. In most cases, inflammation and overt infection are limited to the receiver-stimulator [18], so exploration of the mastoid and middle ear and manipulation of the electrode array is usually not needed.

For patients who present with wound dehiscence associated with device exposure, device removal is typically required; such patients are unlikely to respond to conservative therapy. In one study including nine patients with wound dehiscence associated and device exposure, eight patients required device explantation [3].

●Duration of antibiotic therapy – The optimal duration of antibiotic therapy is not firmly established; the approach should be guided by individual patient circumstances and managed in consultation with an individual with infectious disease expertise [19]. Some treat with a two-week course of parenteral antibiotic therapy (in the absence of evidence for bone infection), without a prolonged course of oral antibiotics. Others advocate initial administration of at least four to six weeks of parenteral antibiotic therapy, after which the scalp over the receiver-stimulator and the postauricular crease should appear healed and the patient should be able to wear the processor without tenderness; thereafter, if there are no plans for implant removal, treatment is continued with long-term suppressive oral antibiotic therapy adjusted for culture and susceptibility results.

The management approach should be tailored to individual patient circumstances (including age, frailty, comorbidities, and the potential impact of implant removal on hearing). As examples, a frail, older adult with a unilateral implant who is a poor candidate for surgical replacement might be maintained on suppressive antibiotic therapy, while a young individual with bilateral implants might undergo implant removal and parenteral antibiotic therapy, followed by implant replacement.

For patients who fail to respond to culture-directed antimicrobial therapy, consideration should be given to the limitations of cultures taken from wound drainage, which may not reflect the microbial profile on the surface of the receiver-stimulator [8]. (See 'Microbiology' above.)

●Persistent or progressive symptoms  

•Review culture data and antibiotic regimen – For patients who fail to respond to culture-directed antimicrobial therapy, consideration should be given to the limitations of cultures taken from wound drainage, which may not reflect the microbial profile on the surface of the receiver-stimulator [8]. In such cases, additional microbiology data (including collection of more specimens and/or addition of molecular testing) should be pursued, with adjustment of the antibiotic regimen accordingly. (See 'Microbiology' above.)

•Device removal – For patients with persistent or progressive symptoms of infection within a few weeks following debridement and treatment with appropriate parenteral antibiotic therapy, device removal (partial or complete) should be pursued [20-22]. In one study, 8 of 11 patients with deep infection ultimately required explantation, including 4 of 7 who had undergone surgical revision as part of the attempt to treat the infection [14].

If the receiver-stimulator is removed but no gross evidence of infection is observed in the middle ear, the electrode may be severed in the mastoid, leaving the intracochlear leads in place to guide future electrode placement; in such cases, the microbial burden on the retained electrode array is likely to be low [18]. For patients who undergo complete device removal (ie, including the electrode array), reimplantation may be difficult due to scarring and cochlear ossification (bone formation in the cochlear scala).

•Completion of antibiotic therapy – Following receiver-stimulator removal, we discontinue parenteral antibiotic therapy and treat with an oral antibiotic regimen (tailored to culture and susceptibility data) for 7 to 10 days postoperatively [19]. After a window of two to three months off of antibiotic therapy with no signs of symptoms of infection, reimplantation may be pursued.

Prevention — Preoperative antibiotic prophylaxis is considered an important tool for reducing the risk of cochlear implant infection; however, no controlled study has shown this intervention to reduce the generally low rate of postoperative surgical site infection or meningitis. (See 'Perioperative antibiotic prophylaxis' below.)

Otitis media — Otitis media can occur in the context of a cochlear implant. General issues related to otitis media in children and adults are discussed in detail separately:

●(See "Acute otitis media in children: Clinical manifestations and diagnosis".)

●(See "Acute otitis media in children: Epidemiology, microbiology, and complications".)

●(See "Acute otitis media in children: Treatment".)

●(See "Acute otitis media in adults".)

Epidemiology — Among children who are predisposed to developing otitis media, risk for both acute and chronic otitis media with effusion persists after cochlear implantation. In one prospective study including 60 children who underwent cochlear implantation, at least one episode of acute otitis media in a mean follow-up of 20 months occurred in 13 out of 34 predisposed to otitis media versus 2 out of 26 who were not predisposed to otitis media prior to cochlear implantation [23]. Otitis media occurred within the first month following implantation in 36 percent. Placement of tympanostomy tube (TT; with or without adenoidectomy) prior to cochlear implantation and presence of normal tympanic membranes with no drainage from the TT for at least two weeks before cochlear implant placement did not decrease the risk of otitis media post implantation.

In adults, acute otitis media following cochlear implant placement is rare. Patients with a history of eustachian tube dysfunction, otitis media with effusion, and/or cholesteatoma prior to cochlear implant placement may occasionally develop transient postoperative otitis media with effusion.

Microbiology — Most cases of otitis media are attributable to respiratory tract pathogens, usually Haemophilus influenzae and Streptococcus pneumoniae [24]. In one study including 615 children with acute otitis media in the post-13-valent pneumococcal conjugate vaccine era, nontypeable H. influenzae was the most common organism isolated by tympanocentesis and 45 percent of the isolates were beta-lactamase positive [25].

Additional issues related to the microbiology of otitis media are discussed further separately. (See "Acute otitis media in children: Epidemiology, microbiology, and complications", section on 'Microbiology' and "Acute otitis media in adults", section on 'Microbiology'.)

Clinical manifestations and diagnosis — Among patients who undergo cochlear implantation, findings of otitis media may include swelling in the postauricular crease and auricular proptosis. In patients who have undergone cochlear implant surgery (including surgical removal of the mastoid cortex), postauricular swelling may reflect bulging of the tympanic membrane (whereas such findings in patients who have not undergone cochlear implant surgery generally reflect mastoiditis). Other tympanic membrane findings consistent with acute otitis media include bulging (with or without erythema) (picture 1) or acute perforation with purulent otorrhea.

A diagnosis of otitis media is established based on clinical manifestations. Some patients warrant further evaluation, including culture of middle ear fluid and/or radiographic imaging:

●Patients with fever and other signs of systemic toxicity should undergo tympanocentesis or myringotomy to collect middle ear fluid for culture prior to initiation of empiric antimicrobial therapy, if feasible; however, this should not cause undue delay in initiation of antibiotic therapy. (See 'Management' below.).

●Radiographic imaging should be pursued in the setting of postauricular swelling (particularly in very young patients, nonverbal patients) or systemic toxicity. Such imaging should consist of CT of the head and temporal bone, with contrast to assess for spread of infection outside the temporal bone (including sigmoid sinus thrombophlebitis, epidural or intradural empyema, or brain abscess).  

Additional issues related to the clinical manifestations and diagnosis of otitis media are discussed further separately. (See "Acute otitis media in children: Clinical manifestations and diagnosis" and "Acute otitis media in adults", section on 'Presentation and diagnosis'.)

Management

●Importance of prompt antibiotic treatment – Among cochlear implant recipients, early diagnosis and prompt treatment of acute otitis media is considered crucial; such patients should not be managed with observation, given the possibility for progression to meningitis (although the risk is relatively low). (See 'Epidemiology' below.)

●Initial approach – The initial management approach depends on a number of factors including the clinical presentation, the type of cochlear implant, the interval since surgery, and individual patient circumstances.

•Oral therapy – Among patients with acute otitis media who meet all of the following criteria, treatment may be undertaken with oral antibiotic therapy:

-The patient underwent cochlear implantation more than two months previously.

-The patient has no history of inner ear dysplasia, such as a “Mondini” malformation.

-The patient does not appear severely ill and has no clinical evidence of mastoiditis or meningitis.

-The patient does not have a cochlear implant that includes a positioner/spacer (Advanced Bionics model AB5100H or AB-5100H-11); such implants were available between 1999 and 2002 but were recalled due to increased risk of meningitis. (See 'Meningitis' below.)

For patients who meet criteria for oral therapy, we treat with amoxicillin-clavulanate for targeted treatment of nontypeable H. influenzae (children: 80 to 90 mg/kg per day orally divided every 12 hours; adults: 875 mg orally every 12 hours) [1,25]. Reasonable alternative agents for patients with beta-lactam hypersensitivity include cefdinir, cefpodoxime, or levofloxacin [1]. (See 'Microbiology' above.)

•Parenteral therapy – For patients who do not meet all of the above criteria, management consists of parenteral antimicrobial therapy. Patients who appear toxic should undergo prompt collection of middle ear fluid for culture (via TT or tympanocentesis) prior to initiation of empiric antimicrobial therapy.

We treat with ceftriaxone (children: 50 to 75 mg/kg/day in one or two divided doses; adults 2 g IV every 12 hours) or cefotaxime (children: 150 mg/kg/day in 3 divided doses; adults: 2 g IV every 4 to 6 hours); for patients who appear toxic we add vancomycin (children: 15 mg/kg/dose every 6 hours; adults 15 to 20 mg/kg every 8 to 12 hours) to include activity against penicillin-resistant pneumococcus. Antibiotic selection should be tailored to susceptibility data when available.

●Persistent or worsening symptoms – For patients with persistent or worsening symptoms after 24 hours of antibiotic therapy, a myringotomy should be performed to facilitate drainage of the middle ear (with or without TT placement) and to obtain middle ear fluid for microbial analysis, if not done previously [1]. In addition, radiographic imaging should be pursued (if not done previously). (See 'Clinical manifestations and diagnosis' above and 'Microbiology' above.)

●Duration of treatment – We administer antibiotics for 10 to 14 days; treatment may be completed with oral therapy (amoxicillin-clavulanate; dosing as above) once patients have improved clinically, are afebrile for at least 24 hours, and able to keep food and medication down.  

Prevention

●Otitis media  

•Vaccination and perioperative prophylaxis – Issues related to vaccination and perioperative antibiotic prophylaxis are discussed below. (See 'Vaccination' below and 'Perioperative antibiotic prophylaxis' below.)

•Role of TT placement and adenoidectomy – In some patients, TT placement and adenoidectomy may help clear otitis media with effusion reduce the risk of acute otitis media; the optimal approach to these interventions is uncertain.

-Our approach – For otitis-prone children or children with persistent middle ear effusion, we favor TT placement (as well as adenoidectomy for children age >3 years) prior to cochlear implant placement; once middle ear inflammation has resolved, we remove the TT and repair the eardrum at the time of cochlear implant placement. (See "Acute otitis media in children: Prevention of recurrence", section on 'Tympanostomy tubes' and "Overview of tympanostomy tube placement, postoperative care, and complications in children".)

-Supporting evidence – The above approach is guided in part by the possibility that TT placement at the time of cochlear implantation may increase the likelihood of implant exposure to recalcitrant pathogens such as MRSA and P. aeruginosa [1]. However, infectious complications after cochlear implantation are rarely associated with presence of TT. In one review including 557 cases of cochlear implantation (including 135 ears with TT placed prior to or after cochlear implantation), there was no difference in the overall rates of infectious complications between those with and without TT; however, the rate of meningitis was higher in the TT group (2.22 versus 0.24 percent) [26]. Similarly, in a retrospective review including 194 patients (of whom 39 had otitis media with effusion treated with TT prior to cochlear implantation, 56 had untreated otitis media with effusion prior to cochlear implantation, and 99 had no otitis media); the rates of early and late postoperative complications were low in all groups [27].

•Education – For patients with otitis media, prompt medical attention is critical to prevent complications. Therefore, patients and their families should be educated about the signs and symptoms of otitis media (fever or earache) or meningitis (fever, headache, vomiting, stiff neck, or change in level of consciousness) and the importance of seeking prompt medical attention if such findings are present.

●Meningitis – Tools for preventing meningitis include prompt treatment of otitis media, if present, and careful cochleostomy sealing at the time of cochlear implantation [16]. Careful cochleostomy sealing (by packing of the cochleostomy with fibrous tissue around the implanted electrode) is important for reducing the likelihood of bacteria spread from the middle ear into the cochlea; this is particularly important for patients with an underlying cochlear malformation [28].

Complications of otitis media

Meningitis — Among patients with cochlear implants who develop otitis media, meningitis can occur as a complication.

General issues related to meningitis in children are discussed separately:

●(See "Bacterial meningitis in children older than one month: Clinical features and diagnosis".)

●(See "Bacterial meningitis in children older than one month: Treatment and prognosis".)

General issues related to meningitis in adults are discussed separately:

●(See "Clinical features and diagnosis of acute bacterial meningitis in adults".)

●(See "Initial therapy and prognosis of community-acquired bacterial meningitis in adults".)

Epidemiology — Among cochlear implant recipients, factors conferring increased risk for development of meningitis include [16,29-34]:

●Age <5 years

●Current or recent episode of otitis media

●Presence of a congenital inner ear dysplasia, such as a Mondini malformation (see "Congenital anomalies of the ear")

●Prior history of meningitis

●Presence of a ventricular shunt or other neurologic prosthesis

●Presence of a cerebrospinal fluid (CSF) leak

●Pneumococcal bacteremia with hematogenous cochlear seeding

●Impaired immune status

●Inadequate cochleostomy sealing at the time of cochlear implantation  

●Use of a positioner or spacer inserted next to the implanted electrode; such devices have been recalled.

In 2002, several cases of bacterial meningitis occurred among patients who underwent cochlear implant placement with insertion of a positioner or spacer inserted beside the electrode to facilitate electrical signal transmission [1,29,35,36]. Such devices were available between 1999 and 2002, when they were recalled. Elective removal of these devices is not recommended [37]. In the United States, the incidence of meningitis associated with these devices was 2.4 to 4.5 cases per 1000 person-years; the odds ratio for infection was 4.5 (95% CI 1.3-17.9) [35,38]. Possible explanations for increased infection risk include larger cochleostomy required for the insertion, introduction of an additional foreign body, inner ear trauma related to placing the positioner (ie, breaching the barrier to the subarachnoid space), and/or incomplete connective tissue seal at the cochleostomy site [29,35].

Since the recall of positioners, available data suggest that the risk of developing bacterial meningitis in the context of otitis media (via intracochlear and intracranial extension) is relatively low [1,16,29,30,35,36]. In one study including 173 pediatric cases of pneumococcal meningitis between 2007 and 2013, one case was associated with cochlear implant [39]. Another study noted an incidence of 11 to 14 cases per 100,000 per year [40]. Vaccination remains an important tool for prevention. (See 'Vaccination' below.)

Microbiology — The microbiology of meningitis associated with cochlear implants often mirrors the microbiology of otitis media; the most common organisms are S. pneumoniae and, less often, H. influenzae [29,35]. Less common organisms include Acinetobacter baumannii, E. coli, and Enterococcus spp [35].

While S. aureus is the main pathogen in surgical site infections (superficial and deep), it is rare for this pathogen to ascend along the electrode, into the inner ear and on to the subarachnoid space to cause meningitis. (See 'Microbiology' above.)

Pseudomonas spp are not typically implicated in meningitis associated with cochlear implants; this pathogen warrants consideration if isolated previously (eg, in the setting of chronic otitis media prior to implant placement), or if Gram stain of middle ear fluid or CSF demonstrates gram-negative rods.

Cochlear implantation does not confer increased risk for Neisseria meningitidis in the absence of other risk factors [1].

Clinical manifestations — The time to onset of meningitis after cochlear implantation ranges from <24 hours to several years after implantation [16]; the risk is highest during the first two months [1,35]. In one review including 26 children with cochlear implants and bacterial meningitis (24 definite and 5 probable episodes), 9 cases occurred within 30 days after surgery, and 20 cases occurred 1.5 months to 2 years after surgery (with 1 exception which occurred at 3 years) [35]. Among the late episodes, 40 percent occurred in patients with acute otitis media at the time of their presentation with meningitis.

Most patients with meningitis present with fever and symptoms and signs of meningeal inflammation (such as nuchal rigidity, headache, and photophobia); additional manifestations may include vomiting or change in level of consciousness. However, the clinical manifestations of bacterial meningitis are variable and nonspecific; no single sign is pathognomonic. Additional details related to clinical manifestations of meningitis are discussed further separately. (See "Bacterial meningitis in children older than one month: Clinical features and diagnosis" and "Clinical features and diagnosis of acute bacterial meningitis in adults".)

Diagnostic evaluation — Cochlear implant recipients with signs of meningitis should be seen urgently by an otolaryngologist with experience in cochlear implant surgery.

The diagnostic evaluation consists of:

●Radiographic imaging (CT of the head and temporal bone, with contrast) to assess for spread of infection outside the temporal bone (including sigmoid sinus thrombophlebitis, epidural or intradural empyema, or brain abscess).  

●Lumbar puncture (CSF should be sent for cell count, Gram stain, and culture); in addition, middle ear fluid should be sent for culture if present [1]. Typical CSF findings are summarized in the table (table 6); the presence of a cochlear implant does not influence the criteria used for diagnosis of bacterial meningitis.

Following collection of specimens for culture, empiric antibiotic therapy should be initiated promptly without awaiting diagnostic test results. (See 'Management' below.)

Additional details related to diagnosis of meningitis are discussed separately. (See "Bacterial meningitis in children older than one month: Clinical features and diagnosis" and "Clinical features and diagnosis of acute bacterial meningitis in adults".)

Management

●Empiric treatment – Management of meningitis consists of parenteral antimicrobial therapy. Selection of empiric antibiotic therapy should be guided by the timing since cochlear implantation:

•In patients presenting >2 months after cochlear implantation, empiric antibiotic therapy should include activity against antibiotic-resistant S. pneumoniae, H. influenzae, and N. meningitidis. Appropriate regimens include vancomycin (children: 60 mg/kg IV divided every 6 hours in children; adult dosing is summarized in the table (table 5)) PLUS either ceftriaxone (children: 100 mg/kg IV divided every 12 to 24 hours; adults: 2 g IV every 12 hours) or cefotaxime (children: 300 mg/kg IV divided every 6 to 8 hours; adults: 2 g IV every 4 to 6 hours).

•In patients presenting ≤2 months after cochlear implantation, empiric antibiotic therapy should include activity against gram-negative pathogens, as well as gram-positive bacteria such as S. aureus (including MRSA) [1,16]. Appropriate regimens include vancomycin (children: 60 mg/kg IV divided every six hours in children; adult dosing is summarized in the table (table 5)) PLUS either ceftazidime (children: 150 mg/kg/day IV every eight hours; adults: 2 g IV every eight hours) or cefepime (children: 150 mg/kg/day divided every eight hours; adults: 2 g IV every eight hours).

●Tailoring antibiotics and treatment duration – Antibiotic therapy should be tailored to findings of CSF and/or middle ear fluid culture data, as needed. The duration of parenteral antibiotic therapy for meningitis due to S. pneumoniae is two weeks; the duration of parenteral antibiotic therapy for meningitis due to H. influenzae is at least one week. The duration of treatment for gram-negative meningitis is at least three weeks or for two weeks after the first negative repeat CSF culture (whichever is longer). Issues related to duration of therapy are discussed further separately. (See "Treatment of bacterial meningitis caused by specific pathogens in adults".)

●Role of corticosteroids – There is no role for routine corticosteroid use. In children, steroids have been associated with benefit in the setting of infection due to H. influenzae type b (Hib). These issues are discussed further separately. (See "Bacterial meningitis in children: Dexamethasone and other measures to prevent neurologic complications" and "Dexamethasone to prevent neurologic complications of bacterial meningitis in adults".)

●Role of surgery – Surgery is warranted only for situations in which the cochlear implant includes a positioner; in such cases, the cochlear implant and electrode array should be removed.

●Adverse event reporting – All cases of meningitis should be reported to the device manufacturer. In the United States, cases should also be reported to MedWatch, the US Food and Drug Administration safety information and adverse event reporting program.

Additional issues related to treatment of bacterial meningitis are discussed in greater detail separately. (See "Bacterial meningitis in children older than one month: Treatment and prognosis" and "Initial therapy and prognosis of community-acquired bacterial meningitis in adults" and "Treatment of bacterial meningitis caused by specific pathogens in adults".)

Prevention — Issues related to prevention of meningitis are discussed above. (See 'Prevention' above.)

Mastoiditis — Among patients with cochlear implants who develop otitis media, mastoiditis (a suppurative infection with destruction of the air cells within the mastoid (figure 2)) can occur as a complication [17].

General issues related to mastoiditis are discussed separately:

●(See "Acute mastoiditis in children: Clinical features and diagnosis".)

●(See "Acute mastoiditis in children: Treatment and prevention".)

●(See "Chronic otitis media and cholesteatoma in adults".)

Epidemiology — In two retrospective studies among children with cochlear implants, the incidence of mastoiditis ranged from 1 to 3.5 percent [41,42]. The time from implant insertion to mastoiditis ranged from months to approximately five years. Given that it may be difficult to distinguish acute otitis media from mastoiditis among patients with cochlear implants, these rates may be viewed with some degree of skepticism.

Acute mastoiditis following cochlear implant in adults is exceedingly rare.

Microbiology — In one review including 43 patients with cochlear implant-associated mastoiditis, the most common organisms were S. pneumoniae, Streptococcus pyogenes, S. aureus, Pseudomonas spp, and H. influenzae [43].

Clinical manifestations — Because cochlear implant placement usually involves removal of the lateral mastoid cortex and mastoid air cells, it may not be possible to differentiate uncomplicated acute otitis media from mastoiditis in the absence of more severe complications.

Clinical manifestations of mastoiditis may include ear pain, fever, auricle protrusion (picture 2), as well as postauricular swelling, erythema, and tenderness (picture 3). Tympanic membrane findings consistent with acute otitis media (bulging, erythema, or perforation with purulent otorrhea) often are present; a normal-appearing tympanic membrane usually (but not invariably) excludes mastoiditis. (See 'Clinical manifestations and diagnosis' above.)

Complications of mastoiditis may include progression of infection to involve adjacent structures including the subperiosteal space, epidural space, subdural space, or brain (figure 3) [44].

Diagnosis — The diagnosis of mastoiditis should be suspected based on clinical manifestations (ear pain, fever, auricle protrusion, characteristic tympanic membrane findings, as well as postauricular swelling, erythema, and tenderness). However, acute otitis media presents similarly.

The diagnostic evaluation consists of:

●Radiographic imaging (CT of the head and temporal bone, with contrast) should be pursued to assess for sigmoid sinus thrombophlebitis, epidural empyema, or subperiosteal abscess that may require drainage.

●Myringotomy to collect middle ear fluid for culture prior to initiation of empiric antimicrobial therapy.

Management — Management of mastoiditis consists of prompt administration of antimicrobial therapy (following myringotomy for drainage of middle ear fluid, to be sent for culture) [41].

●Antibiotic therapy – Appropriate empiric regimens include vancomycin (children: 60 mg/kg IV divided every 6 hours in children; adult dosing is summarized in the table (table 5)) PLUS either ceftriaxone (children: 100 mg/kg IV divided every 12 to 24 hours; adults: 2 g IV every 12 hours) or cefotaxime (children: 300 mg/kg IV divided every 6 to 8 hours; adults: 2 g IV every 4 to 6 hours).

If Pseudomonas spp is a consideration (eg, patient had a prior history of chronic suppurative otitis media, with or without cholesteatoma), ceftazidime (children: 150 mg/kg/day IV every eight hours; adults: 2 g IV every eight hours) or cefepime (children: 150 mg/kg/day divided every eight hours; adults: 2 g IV every eight hours) should be administered rather than ceftriaxone or cefotaxime.

Antibiotic therapy should be tailored to middle ear fluid culture results, if needed.

●Role of surgery – For patients with subperiosteal abscess or persistent symptoms despite antimicrobial therapy, surgical drainage may be needed; however, implant removal is rarely necessary [41,42].

In one review including 43 children with cochlear implants and mastoiditis, surgery was performed in half of cases and included TT insertion, abscess drainage, and/or mastoidectomy [43]. Cochlear implant explantation was required in one case, due to the failure of initial medical and surgical interventions; the patient developed signs suggestive of device malfunction (pain on stimulation).

PREVENTION

General principles — Tools to minimize the likelihood of infection associated with cochlear implants include vaccination against organisms that commonly cause bacterial meningitis and preoperative antibiotic prophylaxis [1,30,45]. These are discussed further below.

Issues related to management and prevention of otitis media are discussed above. (See 'Otitis media' above.)

Vaccination — Vaccination of cochlear implant candidates and recipients is important to reduce the likelihood of bacterial meningitis. Adults should be vaccinated against pneumococcus, and children should be vaccinated against pneumococcus and Hib. In addition, all cochlear implant candidates and recipients should receive other routine age-appropriate vaccines. (See "Standard immunizations for children and adolescents: Overview" and "Standard immunizations for nonpregnant adults".)

Ideally vaccines should be administered at least two weeks prior to surgery [1,46]. If this has not occurred, the indicated vaccines should be administered as soon as possible.

Additional information about vaccines for prevention of meningitis in patients with cochlear implants is available on the United States Centers for Disease Control and Prevention’s website.

Children — All children should receive all doses of the pneumococcal conjugate vaccine and Hib vaccine according to the routine schedule [1].

●Pneumococcal vaccination − Additional details on pneumococcal vaccination are discussed elsewhere. (See "Pneumococcal vaccination in children".)

●Vaccination against H. influenzae − Children <5 years of age should be vaccinated against Hib according to the routine schedule (table 7) [1]. The Hib vaccine is not routinely recommended for cochlear implant candidates >5 years of age since most older children and adults are already immune to Hib, even if they were not previously vaccinated [47]. (See "Prevention of Haemophilus influenzae type b infection", section on 'Routine schedule'.)

Children should be vaccinated against meningococcus according to routine recommendations (ie, they should receive the meningococcal vaccine only if they have a specific indication) [1]. Cochlear implant recipients do not appear to be at increased risk for invasive meningococcal disease. (See "Meningococcal vaccination in children and adults", section on 'Target groups'.)

Annual influenza immunization is recommended for all individuals ≥6 months of age; it is particularly important for cochlear implant recipients and their household contacts to reduce the incidence of otitis media [1]. (See "Seasonal influenza in children: Prevention with vaccines", section on 'Target groups'.)

In addition to the above vaccinations, pediatric cochlear implant candidates and recipients should also receive all routine age-appropriate vaccines (figure 4 and figure 5). (See "Standard immunizations for children and adolescents: Overview", section on 'Routine schedule'.)

Issues related to pneumococcal and Hib vaccines are discussed further separately. (See "Pneumococcal vaccination in children" and "Prevention of Haemophilus influenzae type b infection".)

Adults — Adults who are awaiting or who have undergone cochlear implant placement should receive pneumococcal vaccination. For adults who have never received any pneumococcal vaccine, the United States Centers for Disease Control and Prevention Advisory Committee on Immunization Practices recommends either one dose of the 20-valent pneumococcal conjugate vaccine (PCV20) alone or one dose of the 15-valent pneumococcal conjugate vaccine (PCV15) followed by one dose of the 23-valent polysaccharide pneumococcal vaccine (PPSV23) ≥8 weeks later [48]. For adults who have previously received a pneumococcal vaccine, the recommendations are discussed elsewhere (see "Pneumococcal vaccination in adults", section on 'Approach to recipients of prior pneumococcal vaccines'). Pneumococcal vaccination should be given prior to surgery, when possible. The evidence to support pneumococcal vaccination in adults is discussed in detail separately. (See "Pneumococcal vaccination in adults".)

Annual influenza vaccination is recommended for all adults but is particularly important for cochlear implant recipients and their household contacts to reduce the incidence of otitis media [1]. (See "Seasonal influenza vaccination in adults".)

As noted above, adult cochlear implant candidates and recipients should also receive all routine vaccines (figure 6). (See "Standard immunizations for nonpregnant adults".)

Perioperative antibiotic prophylaxis — Considerations for preoperative antibiotic prophylaxis include prevention of surgical site infection and prevention of otitis media and its complications.

For prevention of surgical site infection, a single antibiotic dose targeting skin flora should be administered parenterally immediately prior to surgical incision [49]. The choice of regimen depends should be guided by patient factors:

●For patients with no risk factors for methicillin-resistant S. aureus (MRSA) colonization (table 8), cefazolin (nonobese adults: 2 g, adults >120 kg: 3 g, children: 25 mg/kg) is the agent of choice [50]. Alternative agents for patients with beta-lactam hypersensitivity include vancomycin (adults: 15 to 20 mg/kg; children: 20 mg/kg) or clindamycin (adults: 600 to 900 mg; children: 20 mg/kg).

●For patients who are known to be colonized with MRSA or who are at risk for MRSA colonization (table 8), vancomycin (adults: 15 to 20 mg/kg; children: 20 mg/kg) is the agent of choice.

For patients with an active or recent history of otitis media, the spectrum of antibiotic prophylaxis should be expanded accordingly:

●For patients with a recent history of acute otitis media or otitis media with effusion, respiratory tract pathogens should be covered with ceftriaxone (adults: 2g; children: 50 mg/kg). This regimen is sufficient for empiric coverage of skin flora in the absence of concern for MRSA colonization (table 8); in presence of such concern, vancomycin (adults: 15 to 20 mg/kg; children: 20 mg/kg) should also be administered.

●For patients with a chronic tympanic membrane perforation, broader gram-negative coverage including activity against P. aeruginosa should be given. Reasonable choices include ceftazidime (adults: 2 g; children 50 mg/kg) or cefepime (adults: 2 g; children: 50 mg/kg). In such cases, vancomycin (adults: 15 to 20 mg/kg; children: 20 mg/kg) should also be administered for empiric coverage of skin flora.

Prophylactic antibiotics should be administered within 60 minutes prior to the surgical incision; however, vancomycin administration should begin within 120 minutes before the surgical incision because prolonged infusion time is required.

General issues related to antimicrobial prophylaxis for prevention of surgical site infection are discussed further separately. (See "Antimicrobial prophylaxis for prevention of surgical site infection in adults".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Cochlear implant infections".)

SUMMARY AND RECOMMENDATIONS

●Definition − Cochlear implants are medical devices that stimulate the auditory nerve in the cochlea (inner ear), allowing people with severe to profound hearing loss to perceive sound. (See 'Introduction' above.)

●Surgical site infection − Careful assessment is needed to distinguish between superficial surgical site infection and deep (implant) infection. (See 'Surgical infection: Superficial versus deep' above.)

•Many patients with superficial infection present indolently, with fever, pain, erythema, swelling, crusting at the incision site, and granulation tissue around the electrode array. Patients with deep (implant) infection can also present with incisional drainage and/or wound dehiscence with implant exposure. (See 'Clinical manifestations' above.)

•Patients with suspected surgical site infection should undergo computed tomography (CT) of the head and temporal bone and any draining fluid from the site should be collected and sent for culture. (See 'Diagnostic evaluation' above.)

•Management consists of oral antibiotic therapy for superficial infections and intravenous therapy for deep infections. Antibiotic regimens should have activity against methicillin-resistant Staphylococcus aureus (MRSA) (table 1 and table 2 and table 3). Management of deep infection also consists of surgical debridement with collection of deep specimens for culture. For patients with persistent or progressive symptoms within a few weeks following debridement and appropriate antibiotic therapy, we suggest device removal (partial or complete) (Grade 2C). (See 'Management' above.)

●Otitis media

•Findings may include swelling in the postauricular crease, auricular proptosis, tympanic membrane bulging (with or without erythema) (picture 1) or acute perforation with purulent otorrhea. For patients with systemic toxicity, middle ear fluid should be obtained for culture and CT should be pursued to assess for spread of infection beyond the temporal bone. CT is also warranted for patients with postauricular swelling. (See 'Clinical manifestations and diagnosis' above.)

•For patients with a cochlear implant who present with otitis media, we recommend prompt antibiotic treatment rather than observation, given risk for progression to meningitis (Grade 1C). (See 'Management' above.)

•Patients who meet all the following criteria may be treated with oral antibiotic therapy:

-cochlear implantation >2 months ago, in absence of positioner

-no history of inner ear dysplasia, and

-nonsevere illness with no evidence of mastoiditis or meningitis

Empiric treatment should include activity against Streptococcus pneumoniae and nontypeable Haemophilus influenzae. We treat with amoxicillin-clavulanate; alternative agents are summarized above. (See 'Management' above.)

•For patients who do not meet the above criteria, we suggest treatment with parenteral antibiotic therapy (Grade 2C). Appropriate regimens include ceftriaxone or cefotaxime; for patients who appear toxic we add vancomycin to include activity against penicillin-resistant pneumococcus. (See 'Management' above.)

●Meningitis

•The diagnostic evaluation consists of a CT to assess for spread of infection beyond the temporal bone, a lumbar puncture, and collection of middle ear fluid for culture. (See 'Diagnostic evaluation' above.)

•In patients presenting >2 months after cochlear implantation, empiric antibiotic therapy should include activity against antibiotic-resistant S. pneumoniae, H. influenzae, and Neisseria meningitidis. Appropriate regimens include vancomycin PLUS either ceftriaxone or cefotaxime. (See 'Management' above.)

•In patients presenting ≤2 months after cochlear implantation, empiric antibiotic therapy should include activity against gram-negative pathogens, as well as gram-positive bacteria including MRSA. Appropriate regimens include vancomycin PLUS either ceftazidime or cefepime. (See 'Management' above.)

•Antibiotic therapy should be tailored to findings of cerebrospinal fluid and/or middle ear fluid culture data, as needed. The duration of treatment should be guided by culture results. (See 'Management' above.)

●Mastoiditis

•Clinical manifestations of mastoiditis may include ear pain, fever, auricle protrusion (picture 2), as well as postauricular swelling, erythema, and tenderness (picture 3). Tympanic membrane findings consistent with acute otitis media (bulging, erythema, or perforation with purulent otorrhea) are often present; a normal-appearing tympanic membrane usually (but not invariably) excludes mastoiditis. (See 'Clinical manifestations' above.)

•The diagnostic evaluation consists of a CT to assess for spread of infection beyond the temporal bone and collection of middle ear fluid for culture. (See 'Diagnosis' above.)

•For most patients with mastoiditis, empiric antibiotic therapy should include activity against antibiotic-resistant S. pneumoniae, H. influenzae, and N. meningitidis; appropriate regimens include vancomycin PLUS either ceftriaxone or cefotaxime. (See 'Management' above.)

•For patients with history of chronic suppurative otitis media, empiric antibiotic therapy should also include activity against Pseudomonas spp; appropriate regimens include vancomycin PLUS either cefepime or ceftazidime. (See 'Management' above.)

•For patients with subperiosteal abscess or persistent symptoms despite antimicrobial therapy, surgical drainage may be needed; however, implant removal is rarely necessary. (See 'Management' above.)

●Prevention

•For otitis-prone children or children with persistent middle ear effusion, we suggest tympanostomy tube (TT) placement (as well as adenoidectomy for children age >3 years) prior to cochlear implant placement (Grade 2C); once middle ear inflammation has resolved, we remove the TT and repair the eardrum at the time of cochlear implant placement. (See 'Prevention' above.)

•All individuals should receive all doses of the pneumococcal conjugate vaccine, H. influenzae type b vaccine, meningococcal vaccine, and influenza vaccine according to the routine schedule. (See 'Vaccination' above.)

•Preoperative antibiotic prophylaxis is important to reduce the risk of surgical site infection as well as otitis media and associated complications. Regimens are summarized above. (See 'Perioperative antibiotic prophylaxis' above.)

ACKNOWLEDGMENTS — The UpToDate editorial staff acknowledges Tahaniyat Lalani, MBBS, MHS, Daniel Sexton, MD, and Debara L Tucci, MD, who contributed to an earlier version of this topic review.