High Frequency of Low-Virulent Microorganisms Detected by Sonication of Implanted Pulse Generators: So What?

INTRODUCTION: Deep brain stimulation (DBS) has become a well-established treatment modality for a variety of conditions over the last decades. Multiple surgeries are an essential part in the postoperative course of DBS patients if nonrechargeable implanted pulse generators (IPGs) are applied. So far, the rate of subclinical infections in this field is unknown. In this prospective cohort study, we used sonication to evaluate possible microbial colonization of IPGs from replacement surgery. METHODS: All consecutive patients undergoing IPG replacement between May 1, 2019 and November 15, 2020 were evaluated. The removed hardware was investigated using sonication to detect biofilm-associated bacteria. Demographic and clinical data were analyzed. RESULTS: A total of 71 patients with a mean (±SD) of 64.5 ± 15.3 years were evaluated. In 23 of these (i.e., 32.4%) patients, a positive sonication culture was found. In total, 25 microorganisms were detected. The most common isolated microorganisms were Cutibacterium acnes (formerly known as Propionibacterium acnes) (68%) and coagulase-negative Staphylococci (28%). Within the follow-up period (5.2 ± 4.3 months), none of the patients developed a clinical manifest infection. DISCUSSIONS/CONCLUSIONS: Bacterial colonization of IPGs without clinical signs of infection is common but does not lead to manifest infection. Further larger studies are warranted to clarify the impact of low-virulent pathogens in clinically asymptomatic patients.

Detection of bacterial DNA on neurostimulation systems in patients without overt infection.

OBJECTIVE: Hardware-related infection remains a major problem in patients with neurostimulation systems. The role of bacterial colonization and the formation of biofilm on the surface of implanted devices remain unclear. Here, we analysed the incidence of bacterial DNA on the surface of implantable pulse generators (IPGs) using 16S rRNA gene sequencing in a consecutive series of patients who underwent routine IPG replacement without clinical signs of infection. PATIENTS AND METHODS: We included 36 patients who underwent scheduled replacement surgery of 44 IPGs. The removed IPGs were processed and whole genomic DNA was extracted. The detection of bacterial DNA was carried out by Polymerase Chain Reaction (PCR) using universal bacterial primers targeting the 16S rRNA gene. The DNA strands were analysed by single-strand conformation polymorphism (SSCP) analysis. RESULTS: Indications for chronic neurostimulation were Parkinson disease, tremor, dystonia, neuropathic pain and peripheral artery occlusion disease. Mean age of patients at the time of implantation was 48 ±â€¯17.6 years. The mean interval between implantation and replacement of the IPG was 24.8 months. PCR/SSCP detected bacterial DNA of various species in 5/36 patients (13.9%) and in 5/44 pacemakers (11.4%), respectively. There was no evidence of clinical infection or wound healing impairment during follow-up time of 45.6 ±â€¯19.6 months. CONCLUSION: Bacterial DNA can be detected on the surface of IPGs of neurostimulation systems in patients without clinical signs of infection by using PCR techniques. It remains unclear, similar to other permanently implanted devices, which mechanisms and processes promote progression to the point of overt infection.

Deep Brain Stimulation-Related Infections: Analysis of Rates, Timing, and Seasonality.

BACKGROUND: Infection is one of the most common complications of deep brain stimulation (DBS). Long-term infection rates beyond the immediate postoperative period are rarely evaluated. OBJECTIVE: To study short- and long-term DBS-related infection rates; to evaluate any potential seasonality associated with DBS-related infections. METHODS: We retrospectively reviewed all DBS surgeries performed in a 5-yr period at 1 hospital by a single surgeon. Infection rates and clinical characteristics were analyzed. Postoperative "infections" were defined as occurring within 6 mo of implantation of DBS hardware, while "erosions" were defined as transcutaneous exposure of hardware at ≥6 mo after implantation. Based on the date of surgery preceding an infection, rates of infection were calculated on a monthly and seasonal basis and compared using Chi square and logistic regression analyses. RESULTS: A total of 443 patients underwent 592 operations; 311 patients underwent primary DBS placement with 632 electrodes. Primary DBS placement infection incidence was 2.6%. DBS procedure infection and infection rate by electrode were 2.9% and 3.2%, respectively. Infectious complications presented later than 6 mo postoperatively in 38% of infected patients Summer (July-September) infection rate was significantly higher than other seasons (P = .002). The odds ratio of an infection related to a surgery performed in August was found to be 4.15 compared to other months (P = .021). CONCLUSION: There is a persistent risk of DBS infection and erosion beyond the first year of DBS implantation. Start of the academic year was associated with increased infection rate at our institution.

Systematic review of hardware-related complications of Deep Brain Stimulation: Do new indications pose an increased risk?

INTRODUCTION: Deep Brain Stimulation (DBS) is an effective treatment extended broadly to many neurological and psychiatric disorders. Nevertheless, complications may arise during DBS procedures or following implantation due to implanted hardware. This may result in both minor and major adverse events that may necessitate hardware removal and/or compromise maximal therapeutic benefit for the patient. OBJECTIVES AND METHODS: To identify relevant literature on hardware-related complications from DBS procedures by performing a systematic review, and propose how to identify at-risk group and possible preventive approaches. RESULTS: Of 4592 abstract screened, 96 articles fulfilled the selection criteria and were reviewed. Overall, the most common hardware-related complications were infections (5.12% of patients), followed by lead migration (1.60%), fracture or failure of the lead or other parts of the implant (1.46% and 0.73%, respectively), IPG malfunctions (1.06% of patients), and skin erosions without infections (0.48% of patients). New indications for DBS, including Tourette's syndrome, cluster headache, and refractory partial epilepsy, were found to bear a higher incidence of hardware-related infections than established indications such as Parkinson's disease. The highest rate of lead fracture or failure was found in dystonia patients (4.22%). Ultimately, the highest rate of pain at the implantation sites was found in refractory partial epilepsy patients (16.55%). CONCLUSION: Our analysis identified a variety of potential hardware-related complications among patients who underwent DBS procedures. Patients who were at risk of complications, such as patients with dystonia and off-label indications (e.g. Tourette's syndrome) should be informed prior to surgery and closely followed thereafter.

Spinal Cord Stimulator Implant Infection Rates and Risk Factors: A Multicenter Retrospective Study.

OBJECTIVES: Spinal cord stimulation is an evidence-based treatment for a number of chronic pain conditions. While this therapy offers improvement in pain and function it is not without potential complications. These complications include device failure, migration, loss of therapeutic paresthesia, and infection. This article looked to establish a modern infection rate for spinal cord stimulators, assess the impact of known risk factors for surgical site infections and to determine the impact of certain preventative measures on the rate of infection. METHODS: After institutional review board approval, a multisite, retrospective review was conducted on 2737 unique implants or revisions of SCS systems. Patient demographics, risk factors including diabetes, tobacco use, obesity, revision surgery, trial length, implant location, implant type, surgeon background, prophylactic antibiotic use, utilization of a occlusive dressing, and post-operative antibiotic use were recorded and analyzed. RESULTS: The overall infection rate was 2.45% (n = 67). Diabetes, tobacco use, and obesity did not independently increase the rate of infection. Revision surgeries had a trend toward higher infection rate; however, this did not meet statistical significance. There was no difference in the rate of infection between implants performed by physicians of different base specialties, cylinder leads vs. paddle leads, or between different prophylactic antibiotics. Implants performed at academic centers had a higher rate of infection when compared to implants performed in nonacademic settings. When patients received an occlusive dressing or post-operative antibiotics they had a lower rate of infection. CONCLUSIONS: The infection rate (2.45%) reported in this study is lower than the previously reported rates (3-6%) and are on par with other surgical specialties. This study did not show an increased rate of infection for patients that used tobacco, had diabetes or were obese. It's possible that given the low overall infection rate a larger study is needed to establish the true impact of these factors on infection. In addition, this study did not address the impact of poorly controlled diabetes mellitus (elevated hemoglobin A1c) vs. well-controlled diabetes. It can be concluded from this study that utilizing an occlusive dressing over the incision in the post-operative period decreases the rate of infection and should become the standard of care. This study also demonstrated the positive impact of post-operative antibiotics in decreasing the rate of infection. Studies in other surgical specialties have not shown this impact which would suggest that further research is needed.

Subsequent Pulse Generator Replacement Surgery Does Not Increase the Infection Rate in Patients With Deep Brain Stimulator Systems: A Review of 1537 Unique Implants at a Single Center.

INTRODUCTION: Deep brain stimulation (DBS) is a well-recognized treatment for patients with movement disorders and other neurological diseases. The implantable pulse generator (IPG) is a fundamental component of the DBS system. Although IPG implantation and replacement surgeries are comparatively minor procedures relative to the brain lead insertion, patients often require multiple IPG replacements during their lifetime with each operation carrying a small but possibly cumulative risk of complications. To better educate our patients and improve surgical outcomes, we reviewed our series of patients at our institution. METHODS: Using electronic health record data, we retrospectively reviewed all initial and subsequent IPG surgeries from patients who underwent at least one IPG surgery between the years of 2010 and 2015 at the Cleveland Clinic main campus. We calculated infection rates for initial IPG implantation surgeries and the infection rate for subsequent replacements. Fisher's exact tests were used to evaluate the chance of an infection between the initial implantation and replacement. Fisher's exact tests and simple logistic regression analyses were used to determine the predictive ability of selected demographic and clinical variables RESULTS: Our final sample included 697 patients and 1537 surgeries. For all patients, the infection rate at the first surgery was 2.01%; at the second surgery, it was 0.44%; and at the third surgery, it was 1.83%. When considering only patients that underwent at least three replacement surgeries (n = 114) the infection rate did not change in a significant manner with subsequent interventions compared to the first replacement. No other variable of interest was a significant predictor of infection. CONCLUSION: We did not find increasing rates of infection with subsequent IPG replacement procedures.

Frame-based stereotactic neurosurgery in children under the age of seven: Freiburg University's experience from 99 consecutive cases.

INTRODUCTION: Stereotactic frame-based procedures proved to be precise, safe and are of widespread use among adult patients. Regarding pediatric patients few data is available, therefore the use of the stereotactic frame remains controversial in this population. This motivated us to report our experience in stereotactic procedures in the youngest patients and review the literature concerning this subject. METHODS: All frame-based procedures performed in patients younger than seven years in the University of Freiburg during the last 10 years were retrospectively analyzed and discussed under the light of the current literature. RESULTS: The studied population was composed of 72 patients under the age of seven (mean 3.4±2.1 years-old), in whom 99 stereotactic procedures were performed. Brain tumor was present in 60 patients, hydrocephalus in five, cystic lesions in three, intracranial abscess in three and epilepsy in one patient. Stereotactic surgery was performed in 36 cases for brachytherapy, in 29 for biopsy, in 20 cases for cyst puncture, in eight for stereotactically guided endoscopic ventriculostomy, in five for catheter placement and in one case for depth electrode insertion. The overall complication rate was 5%. There were three cases of pin penetration through the skull, one case of frame dislocation after extensive cyst drainage and two skull fractures. Neurologic deficit related to frame fixation was observed in none of the cases. In disagreement with other authors, no case of pin related infection, air embolism, hematoma or CSF leak was observed. CONCLUSION: Frame-based stereotactic neurosurgery is a safe technique also in the youngest patients. Rather than the simple use of torque-limiting devices training and experience in the manual adjustment of the stereotactic frame in children have been proven to be crucial factors that contribute to reducing pin related complications.

Reuse of internal pulse generator in cases of infection after deep brain stimulation surgery.

BACKGROUND: Hardware-related infection after deep brain stimulation (DBS) is one of the most serious complications and may need additional interventions. OBJECTIVES: To reuse the internal pulse generator (IPG) after DBS infection and to reduce the economic costs. METHODS: A database of 102 patients who underwent DBS surgery was used in the study. The incidence, clinical characteristics and management of infections while reusing the IPG after DBS-related infection were analyzed and reported. RESULTS: The overall infection rate was 5.9% (6 of 102 patients). Management consisted of total hardware removal followed by intravenous antibiotics. The IPG was at first kept in a solution, then rinsed with water and dried following sterilization with ethylene oxide gas at 38 °C for 18 h. When the treatment of the infection was finished, we reused the IPG and reimplanted the DBS. No hardware-related infection or other complications were observed after reimplantation. CONCLUSIONS: Management of hardware-related infections can be challenging. The medical and economic costs associated with these infections are enormous. The IPG can often be saved in infected patients. Thus, a significant cost burden is eliminated. Properly executed, reuse of IPG should markedly reduce the costs of these devices.

Surgical lead extraction for total occlusion of the superior vena cava by chronic lead infection after mustard procedure.

We present a case of total occlusion of the superior vena cava (SVC) with extensive thrombosis of the adjacent large veins secondary to multiple abandoned pacemaker leads with a superimposed chronic lead infection by Corynebacterium jeikeium. A surgical lead extraction was performed with an extensive en-bloc resection of the SVC together with the right subclavian vein and the right innomate vein. No venous reconstruction was required because of an unobstructed runoff via a well-developed azygos system.

Vacuum assisted vegetation extraction for the management of large lead vegetations.

BACKGROUND: Complete device and lead removal is recommended for management of infected implantable cardiac device. Management of large lead vegetation (2 cm) is still in debate. METHODS: We report a series of patients involving percutaneous extraction of large vegetations (>2 cm) from ICD/pacing leads using the AngioVac Cannula in patients with infective endocarditis. This approach was used to debulk the ICD/pacing lead vegetations in order to minimize the risk of septic pulmonary embolism during lead explantation. CONCLUSION: AngioVac Cannula can be used safely and effectively as an adjunctive method for patients with large lead vegetation.

[Biomaterials in cochlear implants]. / Biomaterialien bei Cochlea-Implantaten.

Cochlear implants (CI) represent the "gold standard" for the treatment of congenitally deaf children and postlingually deafened adults. Thus, cochlear implantation is a success story of new bionic prosthesis development. Owing to routine application of cochlear implants in adults but also in very young children (below the age of one), high demands are placed on the implants. This is especially true for biocompatibility aspects of surface materials of implant parts which are in contact with the human body. In addition, there are various mechanical requirements which certain components of the implants must fulfil, such as flexibility of the electrode array and mechanical resistance of the implant housing. Due to the close contact of the implant to the middle ear mucosa and because the electrode array is positioned in the perilymphatic space via cochleostomy, there is a potential risk of bacterial transferral along the electrode array into the cochlea. Various requirements that have to be fulfilled by cochlear implants, such as biocompatibility, electrode micromechanics, and although a very high level of technical standards has been carried out there is still demand for the improvement of implants as well as of the materials used for manufacturing, ultimately leading to increased implant performance. General considerations of material aspects related to cochlear implants as well as potential future perspectives of implant development will be discussed.

Pulmonary valve replacement for pacing electrodes related bacterial endocarditis.

Infective endocarditis of pulmonary valve requiring surgery is rare. We report a case of 80-year-old woman with a permanent pacemaker implanted 14 years ago. She had signs of infection resistant to antibiotic therapy, secondary cachexia, and dyspnea. Echocardiography examination revealed an infectious mass on pacing electrodes in the right atrium, right ventricular dysfunction, and pulmonary hypertension. Removal of the infected pacing system was indicated. During the operation, destruction of the pulmonary valve due to bacterial endocarditis was diagnosed. Replacement with a stented porcine valve was performed. The patient was discharged on postoperative day 20. Seven months after the operation, the patient is in a good condition.

[How to treat infected pacemaker leads in very elderly patients].

Infection of pacemaker leads is one of the difficult problems after implantation, especially in elderly patients. Three octogenarians were referred to our hospital due to infection of pacemaker leads which had been resistant to antibiotic treatments. The patients were 81 approximately 88 years old including 1 male and 2 females. Primary implantation of pacemaker had been performed 9 months approximately 16 years before and infection had started 7 months approximately 7 years before. The infected leads were partially resected in an 88-year-old woman who had serious dementia and poor nutrition status. The infected leads were completely removed under cardiopulmonary bypass (on-beating) in an 81-year-old woman who had undergone 3 previous surgical treatments. The infected lead was partially removed in an 82-year-old man, but infection was not perfectly controlled. Therefore, the lead was completely removed under cardiopulmonary bypass with cardiac arrest. In conclusion, complete removal of the whole pacemaker system is desirable, while palliative surgery might be an option for very elderly patients with high risks.

[Removal of infected pacemaker leads under extracorporeal circulation].

We report 3 cases of removal of infected pacemaker leads under extracorporeal circulation. The infections occurred 12, 29, and 58 months after the implantations. A skin ulcer was at first formed over the pacemaker; then the pacemaker itself became infected. The right atrium was incised, and the infected leads were pulled out. The ventricular leads adhered to the tricuspid valve, the chordae tendineae and the endocardia. A lead tip could easily be extirpated with sharp scissors. Two cases underwent implantation of myocardial electrodes; the new generators were implanted below the fascia of the rectus abdominis muscle. In the other case, a pacemaker was implanted transvenously because an appropriate epicardial pacing site could not be found. Case infected by methicillin-resistant Staphylococcus aureus (MRSA) died from mediastinitis a month after the operation. The others did not have a recrudescence of their infections. Removal of the leads under extracorporeal circulation is an invasive but sure procedure to extirpate.

Biocompatibility of an enzyme-based, electrochemical glucose sensor for short-term implantation in the subcutis.

BACKGROUND: Continuous glucose measurements provide improved glycemic control and may prevent hypoglycemia and long-term complications of diabetes. One of the most promising techniques is the short-term implantation of electrochemical glucose sensors in subcutis. However, the inflammatory reaction to these sensors may lead to bioinstability of sensor measurements. The purpose of the present investigation was to examine factors contributing to the observed subcutaneous inflammatory reaction to an enzyme-based electrochemical glucose sensor for continuous glucose measurements. The sensor biocompatibility was assessed in vitro and in vivo. METHODS: A toxicological assessment was performed on sensor materials and leachables, and the endotoxin content of sensors was determined by a Limulus amoebocyte lysate (LAL) test. Moreover, as a consequence of permanent penetration of the skin by the sensor the role of bacterial migration to the tissue was investigated. In vivo biocompatibility was investigated through histological examination of implanted sensor membranes for 3 days in pigs. Additionally, the effect of needle size and type (normal vs. inserter needle) on tissue trauma at sensor insertion was evaluated, and the healing of subcutis was assessed histologically from 3 to 14 days after removal of sensors. RESULTS: The toxicological assessment and the LAL test showed no concerns in a 3-day implantation scenario, and bacterial migration to the subcutis could not be detected. The histological examination showed that a reduction in needle size reduced the extent of inflammation to very low levels, and that the different sensor membranes showed similar extent and type of inflammation. Additionally, the extent of subcutaneous tissue reaction after removal of sensors declined gradually over time and returned to near-normal levels after 2 weeks. CONCLUSION: The electrochemical enzyme-based glucose sensor for continuous glucose measurements in subcutis is acceptable from a biocompatibility point of view. Reducing the inserter needle in size reduces the trauma induced at sensor implantation to neglible levels. Furthermore, the tissue reaction to the sensor returns to near-normal 2 weeks after the sensor has been removed following a 3-day implantation period.

Nosocomially acquired Pseudomonas stutzeri brain abscess in a child: case report and review.

Pseudomonas stutzeri is a rare cause of nosocomial infection. We report a pediatric case of nosocomially acquired P. stutzeri brain abscess after subdural grid implantation before surgery for refractory epilepsy and review the literature.

Incidence and prognosis of pacemaker lead-associated masses: a study of 1,569 transesophageal echocardiograms.

UNLABELLED: Endovascular lead infection is an uncommon but serious problem. Transesophageal echocardiography (TEE) is a useful tool for identification of pacemaker lead vegetations. Additionally, incidental echogenic masses are occasionally identified by TEE. The prognosis and optimal treatment of either suspected lead infection or an incidental mass is poorly understood. OBJECTIVE: The purpose of this study was to examine the incidence and clinical course of pacemaker lead masses. METHODS: A total of 1,569 sequential TEE examinations performed from January 2002 to January 2005 were reviewed. Retrospective chart analysis of patients with a pacing lead-associated mass was performed to review the indication for TEE as well as clinical management. Telephone follow up was also performed. RESULTS: During 125 TEE examinations, pacemaker leads were visualized in the right-sided chambers. Fifteen studies demonstrated an echogenic mass associated with the lead. In 9 of these studies, endocarditis was suspected, and the mass was felt to be a vegetation: 6 were treated with antibiotics alone, with 1 death attributed to a complication of endocarditis (autopsy proven massive pulmonary embolus); 3 patients were treated with lead extraction, both were alive at follow up; 1 patient was lost to follow up after the TEE. Six patients (5%) were found incidentally to have a mass on the pacing lead during TEE: 3 were treated with warfarin; 2 received no specific therapy; and 1 underwent surgical debridement of the lead during valve surgery. All of the patients in this group were alive at follow up, and no significant clinical events attributable to the lead-associated mass were observed. CONCLUSIONS: TEE identified an echogenic mass on 12% of the leads imaged, with 60% having suspected endocarditis. The mortality rate of lead vegetation was 11%. An incidental mass was noted on 5% of the leads, with no significant associated morbidity or mortality observed.

Chronic Pseudomonas infections of cochlear implants.

OBJECTIVE: To discuss chronic, refractory Pseudomonas infections of cochlear implants and their management. DESIGN: Retrospective case series. SETTING: Two university-based cochlear implant programs. PATIENTS: Twenty-eight-year-old (Case 1) and 4-year-old (Case 2), different devices. INTERVENTIONS: Medical and surgical management. MAIN OUTCOME MEASURES: Clinical course. RESULTS: Both patients had delayed presentations, 4 months and 3 years postimplantation, respectively, with fluctuating scalp edema and pain resistant to multiple courses of oral antibiotics. Infections began as localized granulation and progressed to complete encasement of both devices with rubbery, poorly vascularized tissue. In each case, two different strains of multiresistant Pseudomonas aeruginosa were cultured. Infections progressed despite local debridement and targeted antipseudomonal antibiotic coverage, and sensitive organisms continued to appear in cultures of refractory granulation tissue. Both patients underwent partial explantation, with the electrode array left in the cochlea, then received 2 to 3 more months of further medical therapy and observation and then were reimplanted successfully with new devices. Both have shown excellent performance and no sign of recurrent infection. CONCLUSIONS: Infections of cochlear implants are uncommon, and cases of successful conservative management without device explantation have been reported. However, our experience and the implanted device literature suggest that chronic Pseudomonas infections may represent a distinct clinical entity, likely to fail protracted therapy and ultimately require device removal. Fortunately, successful reimplantation is possible.

Usefulness of routine epicardial pacing wire culture for early prediction of poststernotomy mediastinitis.

Poststernotomy mediastinitis (PSM) is one of the most serious complications of cardiac surgery, and its associated morbidity and mortality demand early recognition for emergency therapy. In this study, we investigated the usefulness of epicardial pacing wire (EPW) cultures for the prediction of PSM. Among 2,200 patients who underwent a cardiac surgical procedure at our hospital between 1 January 1999 and 31 December 2001, 82 (3.7%) had PSM; Staphylococcus aureus was the organism (45.1%) most frequently isolated at the time of surgical debridement. EPWs from 1,607 (73.0%) patients, 73 (4.5%) of whom developed PSM, were cultured. EPW cultures from 466 (29.0%) were positive, most often (74.9%) for coagulase-negative Staphylococci. EPW cultures were truly positive in 26 cases, truly negative in 1,106 cases, falsely positive in 428 cases, and falsely negative in 47 cases (with sterile cultures in 35 cases and a culture positive for an organism different from that isolated at the time of debridement in 12 cases). EPW culture had a positive predictive value of only 5.7% and a high negative predictive value (95.9%) for the diagnosis of PSM, with an accuracy of 70.4%. However, the likelihood ratio of positive (1.27) and negative (0.89) tests indicated only small changes in pretest-to-posttest probability. Therefore, a strategy of routine culture of EPWs to predict PSM seems questionable.

Histologic evaluation of the tissue seal and biologic response around cochlear implant electrodes in the human.

HYPOTHESIS: Histopathologic study of the tissue seal and biologic response around cochlear implant electrodes in patients who had received a cochlear implant during life could provide clues concerning the pathogenesis of meningitis after cochlear implantation. BACKGROUND: Bacterial meningitis has been reported as an infrequent complication of cochlear implantation using a variety of electrode designs. The cause of meningitis in cochlear implant recipients has not been firmly established. In an analogous surgical situation, namely stapedectomy, delayed meningitis could occur as a complication of ipsilateral acute suppurative otitis media in which there was open communication between the middle ear and perilymph. METHODS: Twenty-one temporal bones from 20 individuals who had undergone cochlear implantation during life were studied by light microscopy. All sections passing through the cochleostomy site and electrode track were examined to evaluate the tissue seal at the cochleostomy, the presence or absence of an extracochlear electrode sheath, and finally, to seek evidence of a cellular inflammatory response near the electrode. These data were compared with clinical data, including electrode system used, the number of years between implantation and death, type of tissue used at surgery, and the age and sex of the patients. RESULTS: The 21 specimens included cases implanted with the Symbion Ineraid, Cochlear Corporation Nucleus 22-channel, Cochlear Corporation Nucleus 24-channel, a Cochlear Corporation Nucleus single channel, and Advanced Bionics Clarion C1 devices. At the cochleostomy site, and just within the cochlea, there was a robust fibrous and bony tissue response in all 21 ears and in most cases, there was a fibrous sheath surrounding the electrode in the middle ear. No recognizable open communication or potential communication between the middle ear and the inner ear was seen in any of the 21 ears. An inflammatory cellular response, including mononuclear leukocytes, histiocytes, and foreign body giant cells, were present in 12 of the 21 temporal bones (57%) and was most intense at the cochleostomy site. No statistically significant relationship was found between the presence or absence of inflammatory cells and the type of tissue graft used at surgery. CONCLUSIONS: The histologic evidence presented in this study does not support open communication between the middle and the inner ear as part of the pathogenesis of bacterial meningitis as a late complication after cochlear implantation. Rather, the finding of a cellular inflammatory response in 12 of 21 temporal bones suggests that late hematogenous contamination and colonization of the implant is a much more likely pathogenic mechanism. This putative mechanism has implications for possible strategies to prevent meningitis after cochlear implantation.