Intracerebral abscess is a life-threatening neurosurgical condition. Reference Aras, Sabanci and Izgi2 Advances in neuroimaging, stereotaxy, pathogen isolation/sequencing, and antibiotic therapy have improved care of patients with intracerebral abscess. Reference Aras, Sabanci and Izgi2,Reference Nathoo, Nadvi, Narotam and van Dellen3 However, case fatality rates vary from ∼10% to 25%. Reference Helweg-Larsen, Astradsson, Richhall, Erdal, Laursen and Brennum4–Reference Amornpojnimman and Korathanakhun8 Abscess development may occur via contiguous spread of local infection or hematogenous spread of systemic infection. Risk factors include immunosuppression, immunodeficiency, disruption of brain protective barriers, and prior cranial neurosurgical intervention. Reference Brouwer, Tunkel, McKhann and van de Beek1,Reference Brook9 Abscess-associated complications include hydrocephalus, acute ventriculitis, and epilepsy Reference Brouwer, Tunkel, McKhann and van de Beek1,Reference Aras, Sabanci and Izgi2,Reference Brouwer and van de Beek10 and therefore prompt identification of abscesses that will benefit from surgical intervention is crucial.
Two commonly utilized approaches to surgical management include (1) craniotomy for complete excision of abscess contents and capsule and (2) burrhole aspiration with or without stereotactic guidance. Reference Aras, Sabanci and Izgi2,Reference Brouwer and van de Beek10–Reference Gadgil, Patel and Gopinath14 Many surgeons believe complete excision of the abscess and associated capsule may offer improved source control and penetration of antibiotics (i.e., following resection of collagenous abscess capsule). Prior reports indicate this may lead to lower abscess recurrence rates, decreased length of hospital stay, decreased overall cost, and shorter length of antibiotic requirement. Reference Aras, Sabanci and Izgi2,Reference Gadgil, Patel and Gopinath14–Reference Mut, Hazer, Narin, Akalan and Ozgen16 In contrast, abscess aspiration alone may provide a microbiological diagnosis, reduce mass effect, and minimize the risk of morbidity (i.e., neurovascular injury, intracerebral hemorrhage, delayed-onset epilepsy. Reference Zhang, Hu, Wu, Hu, Ding and Lu5,Reference Mut, Hazer, Narin, Akalan and Ozgen16–Reference Ratnaike, Das, Gregson and Mendelow18 However, to date there have been no randomized controlled trials comparing these approaches. Reference Nathoo, Nadvi, Narotam and van Dellen3 Furthermore, indications (e.g., lesion size, location, single or multiple, primary or recurrent) and timing for surgery remain unclear.
To date, there are no widely accepted neurosurgical guidelines, and no standard practices have been adopted by the greater neurosurgical community. Here, we investigate Canadian practice patterns for the medical and surgical management of primary, recurrent, and multiple intracerebral abscesses. Identifying heterogeneity or consensus in national practice patterns may inform the development of national standard guidelines.
Study Design and Population
The Canadian Neurosurgery Research Collaborative (CNRC) is led by resident neurosurgeons, uniquely positioned to capture multicenter data to address the multidimensional knowledge gaps pertaining to the medical and surgical management of neurosurgical entities such as primary, recurrent, and multiple intracerebral abscess. We conducted a self-administered, cross-sectional electronic survey of Canadian staff and resident neurosurgeons. Board-certified fellows were also eligible. Institutional ethics review board approval was obtained prior to survey development. A local chart review was performed, and anonymized data were utilized during the development of case examples subsequently included in the survey. All data during survey development and administration were collected and stored on a secure REDCap server.
Survey design was iterative and completed by the primary investigators (MKS, TD, and KR). The initial survey draft was assessed for redundancy and clarity by the steering committee of the CNRC. Reference Dakson, Tso and Ahmed19 Face and content validity were assessed via board-certified neurosurgeons at multiple sites.
The anonymous, voluntary survey was distributed by email to all active members of the Canadian Neurosurgical Society (CNSS) and CNRC over a scheduled 8-month period with several email reminders. A final personal communication via local CNRC member to their colleagues was completed over the 2-month period prior to survey closure. We anticipated 175 potential respondents across both targeted groups.
Descriptive data were tabulated. Responses between subgroups (e.g., adult vs pediatric practice, staff vs. resident, years in practice) were analyzed using the Chi-square test with statistical significance set at p < 0.05. A 7-point Likert scale was provided for determining the self-perceived response confidence. Free text responses were analyzed qualitatively. Categorical data were reported as counts and percentages.
In total, 101 respondents (57.7%) completed the survey. The majority (60.0%) were attending staff neurosurgeons working in an academic, adult care setting (80%) (Figure 1). Thirty-four percent of respondents were neurosurgical residents. Twenty-seven percent of attending staff reported being in practice for between 11 and 20 years. The majority of respondents (47.5%) reported managing between 26 and 50 patients in consultation per week. Responses were widely distributed across Canadian centers. The majority (63.4%) of respondents reported managing either one or zero intracerebral abscess per month.
Guidelines and Recommendations
A minority of (23.8%) respondents indicated that they are aware of general guidelines for the management of intracerebral abscesses (Table 1). Several respondents further elaborated further that their practice was informed by Infectious Disease Society of America (IDSA) or American Association of Neurosurgery (AANS) guidelines. The majority of respondents (77.2%) agreed (i.e., somewhat, mostly, or entirely) with a theoretical recommendation that neurosurgical management is indicated for any brain abscess measuring at least 2.5 cm in diameter. Fifty two (51.5%) recommended this approach for all patients with intracerebral abscess they managed during the 6 months preceding survey completion. Clinicians disagreeing with this indication provided cases in which they would not offer neurosurgical treatment: abscesses in the early cerebritis stage, avoiding aggressive therapy in patients who may not tolerate surgery, abscesses in deep or inaccessible locations, and known microbial etiology with improvement on antibiotic therapy.
Surgical Technique and Indications
Most respondents (67.3%) chose a surgical technique (i.e., aspiration vs evacuation and resection of abscess capsule) based on assessment of clinical and radiological factors (Table 1). The majority of respondents favored of excising an intracerebral abscess over performing aspiration if located superficially in non-eloquent cortex (60.4%), located in the posterior fossa (65.4%), or causing mass effect leading to herniation (75.3%) (Figure 2). Choice of surgical technique was equivocal if there was a high suspicion of nocardia, tuberculous, fungal, or branching bacteria, or when the abscess capsule appears radiologically mature. Fifty-eight percent (57.4%) of respondents were not in favor of open resection to prevent ventriculitis when an abscess is abutting but has not yet ruptured into the ventricular system. The majority of respondents agreed with the published management recommendations in each scenario as visualized in Figure 2B.
Intraoperative Antibiotic Use
Half of our respondents (54.5%) felt there is a role for antibiotics administration directly into the abscess cavity (Figure 3). Although half (53.5%) believed vancomycin powder should be applied to the cavity following excision, 81.2% had not applied vancomycin powder for any intracerebral abscess excision case during the 6-month period prior to survey completion. While 42 (41.6%) surgeons agreed that synthetic duraplasty should not be used if a craniotomy is performed for evacuation of an intracerebral abscess, 30 (29.7%) respondents were uncertain. The primary exception stated by most respondents was in cases where a watertight closure was needed and pericranium could not be harvested.
Multiple and Recurrent Abscesses
Most respondents (81.2%) reported that in situations involving multiple abscesses the largest one should be aspirated for culture and antibiotic sensitivities (Figure 4). A third of respondents (30.7%) implemented this guideline in more than half of their recent cases. Eighty-nine respondents (88.1%) indicated that choosing to aspirate additional lesions would depend on other factor such as lesion size, maturity, surrounding edema, patient’s symptoms, and prior response to antimicrobials.
Most respondents were in favor of reoperation for recurrent abscesses if the recurrence measured greater than 2.5 cm, there was significant neurological deterioration, the prior operation was an aspiration and did not include resection of the abscess capsule, and if recurrence occurred despite maximal antibiotic therapy after the index surgery (Figure 5). Subtotal resection (85.2%) and goals of care that include “doing everything possible to save a patient’s life” (62.4%) were not considered stand-alone indications for repeat intervention by most respondents.
Clinical Case Scenarios
The most common goal of surgery in all three clinically distinct cases of intracerebral abscesses was identification of the organism (Figure 6). Regarding Case 1 (i.e., multiple intracerebral abscesses), 40.6% of respondents would recommend stereotactic aspiration of any abscesses greater than 2.5 cm in diameter on radiographic imaging. Regarding Case 2 (i.e., intraventricular rupture of abscess), 32% of respondents recommended surgical excision of abscess and insertion of an external ventricular drain (EVD). Regarding Case 3 (i.e., pediatric intracerebral abscess from otitis media), 39 (38.6%) respondents recommended stereotactic aspiration of the largest abscess only (Figure 7).
We compared responses between groups according to type of practice (i.e., pediatric vs adult practice), position (i.e., residents vs attending staff), years in practice (greater or less than 10 years), number of abscesses managed per month (0 or 1 vs greater than 1), and awareness of guidelines (Supplementary Table 1). A greater proportion of respondents with less than 10 years in practice and awareness of guidelines were more likely to recommend abscess excision compared to aspiration alone. A greater proportion of respondents practicing pediatric neurosurgery, residents, and those with less than 10 years in practice were more likely to recommend excision of abscesses in non-eloquent locations. Residents and those in practice with less than 10 years of experience favored excision for situations where abscesses produce a mass effect resulting in herniation. When the abscess capsule was perceived as “thick” and radiologically “mature,” significantly more adult neurosurgeons compared to pediatric surgeons recommended craniotomy and excision over aspiration; whereas a greater proportion of residents and those in practice for less than 10 years in practice recommended excision.
A greater proportion of attending staff felt there was no role for antibiotic administration into the abscess cavity, including using vancomycin in an open excision, compared to residents. Respondents who saw at least one intracerebral abscess a month were more likely to rely on additional factors including size, maturity, surrounding edema, and response to antimicrobial treatment when deciding to aspirate additional lesions aside from the largest lesion. Regarding Case 1 (i.e., multiple abscesses) and Case 3 (i.e., pediatric abscess), we did not identify statistically significant differences across subgroups (Supplementary Tables 2 and 4). In Case 2 (i.e., intraventricular rupture), a greater proportion of those with > 10 years in practice (compared to <10 years), attending staff (compared to residents), with greater than 1 abscess (compared to 0–1) seen in consultation per month, and perceived awareness of guidelines (Supplementary Table 3) observed significant differences between subgroups (p < 0.001). Attendings and those with >10-years experience were more likely to stereotactically aspirate where residents wand fellows would surgically excise. Whereas clinicians who manage more than 1 abscess per month were more likely to excise rather than stereotactically aspirate.
To date, there are no widely accepted neurosurgical guidelines for management of intracerebral abscess. Despite the lack of standard practices among the greater neurosurgical community, no randomized controlled trials comparing common surgical techniques (e.g., craniotomy for excision of abscess vs. stereotactic aspiration via burr holes) have been completed. This cross-sectional national survey of Canadian neurosurgery attending staff and residents captures practice patterns regarding the medical and surgical management of primary, recurrent, and multiple intracerebral abscesses. We identified few areas of consensus and significant heterogeneity in practice patterns. These results may inform development of national practice guidelines.
Indications for neurosurgical intervention include significant mass effect, intracranial hypertension, progressive neurologic deficit, and pathogen identification. Reference Arlotti, Grossi and Pea20 While surgery is generally considered a mainstay of treatment, medical treatment alone may be appropriate. Such instances include small abscesses (<2.5 cm), good initial neurological status, known pathogen, and when the patient is a poor surgical candidate. Reference Arlotti, Grossi and Pea20,Reference Mameli, Genoni, Madia, Doneda, Penagini and Zuccotti21
Although there are no current, widely accepted neurosurgical guidelines for the management of intracerebral abscess, approximately a third of respondents indicated they were aware of general guidelines (e.g., IDSA). Most respondents in this study agreed with the theoretical recommendation that any abscesses larger than 2.5 cm should be operated on. However, few respondents reported implementing this practice for abscesses they recently managed. A patient with a larger abscess may be a candidate for conservative management if there were significant contraindications to surgery, refusal of surgery, or the abscess is in the early cerebritis stage. On the other hand, select abscesses smaller than 2.5 cm may be also be amenable to surgery. The 2.5 cm size cutoff is commonly cited but unfortunately lacks objective evidence to support an impact on functional outcome and overall survival. Reference Brook9,Reference Brouwer and van de Beek10,Reference Arlotti, Grossi and Pea20,Reference Brouwer, Tunkel, McKhann and van de Beek1,Reference Mamelak, Mampalam, Obana and Rosenblum22 Respondents also felt that lesion location (e.g., non-eloquent, eloquent, deep, posterior fossa), high suspicion for fungal or atypical bacterial species (e.g., nocardia or tuberculous disease), radiographic appearance, and symptomatic mass effect leading to herniation were also important considerations in the surgical management of intracerebral abscesses.
The optimal surgical technique for management of intracerebral abscess is a topic of ongoing debate. Reference Wu, Wei and Yu23,Reference Makwana, Merola, Bhatti, Patel and Leach24 Advantages and disadvantages of each technique have been reported including the challenges and experiences in developing countries. Reference Singh, Rohilla and Kumawat25 In the literature, abscess excision has been observed to be associated with decreased recurrence and re-operation rates, decreased duration of antibiotic course, shorter hospital stays, and lower overall cost relative to aspiration. Reference Aras, Sabanci and Izgi2,Reference Moorthy and Rajshekhar13–Reference Mut, Hazer, Narin, Akalan and Ozgen16,Reference Ratnaike, Das, Gregson and Mendelow18,Reference Wu, Wei and Yu23 Excision may be preferred in cases of large, superficial, or multiloculated abscesses, when there is significant mass effect, in trauma- and/or foreign body associated abscesses, and those located in the posterior fossa. Reference Aras, Sabanci and Izgi2,Reference Ratnaike, Das, Gregson and Mendelow18,Reference Kural, Kırmızıgoz, Ezgu, Bedir, Kutlay and Izci26 We identified further suggestions for excision over aspiration including abscesses in non-eloquent areas of the brain, with suspicion of more resistant pathogens such as fungi, TB, or branching bacteria. Reference Brouwer, Tunkel, McKhann and van de Beek1 However, excision has been associated with an increased rate of mortality, Reference Ratnaike, Das, Gregson and Mendelow18 intracranial hemorrhage, Reference Makwana, Merola, Bhatti, Patel and Leach24 and seizures. Reference Aras, Sabanci and Izgi2 Advantages of aspiration include minimally invasive technique, potential to avoid general anesthesia in poor surgical candidates, less potential morbidity and mortality, and use in deep-seated or eloquent areas. Reference Aras, Sabanci and Izgi2,Reference Gadgil, Patel and Gopinath14,Reference Ratnaike, Das, Gregson and Mendelow18,Reference Kural, Kırmızıgoz, Ezgu, Bedir, Kutlay and Izci26 The largest drawback of aspiration is that the abscess capsule remains in situ and may lead to higher rates of early recurrence and need for re-operation. Reference Aras, Sabanci and Izgi2,Reference Gadgil, Patel and Gopinath14,Reference Wu, Wei and Yu23
Most of our survey respondents agreed that either aspiration or excision may be an acceptable approach depending on specific clinical and radiographic factors. There remained a preference for less invasive techniques, however, as a much larger proportion of surgeons used aspiration (30.7%) compared to excision (2%) exclusively. Choice of procedure was equivocal if the abscess abuts the ventricle, with more resistant pathogens, and a more radiologically mature capsule. Of particular interest was the discordance in responses between experienced surgeons and residents, those < 10 years into practice, and those managing 0–1 abscesses per month. Specifically, while more experienced surgeons were less likely to excise an abscess in a non-eloquent area, they were more likely to resect an abscess that appears radiologically mature with a “thick” capsule and less likely to use topical antibiotics in the abscess cavity following excision (e.g., vancomycin powder) (Supplementary Table 1).
Additional unresolved issues investigated in this study include intraoperative antibiotic administration and use of synthetic duraplasty in the setting of intracerebral abscess. Some experts advised intra- or postoperative administration of antibiotics into the abscess cavity as penetration through the abscess capsule may be limited during an aspiration procedure. Reference Xiao, Tseng, Teng, Tseng and Tsai7 Some authors observed good clinical and radiological outcomes with the use of intracavity antibiotics and suggest their utility in large, poorly resolving abscesses, or those involving more resistant pathogens; however, evidence is limited. Reference Broggi, Franzini, Peluchetti and Servello27–Reference Mathisen and Johnson30 In our study, we found that most Canadian neurosurgeons did not routinely utilize intraoperative intracavitary antibiotics unless for repeat procedures.
Approach to Multiple Abscesses
For confirmed intracerebral abscess, the incidence of multiple lesions ranges from 10% to 50%. Reference Mameli, Genoni, Madia, Doneda, Penagini and Zuccotti21,Reference Burke, Thawani and Berger31–Reference Mampalam and Rosenblum35 Patient presentation depends on multiple factors: abscess location (i.e., eloquence), size and mass effect, and stage of abscess formation. When there are multiple small brain abscesses (<2.5 cm), Brouwer et al. advocate for diagnostic aspiration of the largest lesion, with subsequent decision to aspirate other abscesses made based on their size, extent of surrounding edema, patient’s symptoms, and response to broad-spectrum anti-microbial therapy. Reference Brouwer and van de Beek10 Given the apparent higher mortality rate with multiple abscesses, more aggressive management may be required to achieve source control. Reference Dyste, Hitchon, Menezes, VanGilder and Greene33 Mamelak et al. suggest an algorithm with aspiration of all abscesses >2.5 cm on an urgent basis with antimicrobials held until surgical specimens are obtained in the patient with no primary source of infection. Reference Mamelak, Mampalam, Obana and Rosenblum22 Interestingly, the conservative cutoff of 2.5 cm for surgical intervention in the nonearly cerebritis phase intraparenchymal abscess was first advocated by Mamelak et al. using Rosenblum et al. finding that solitary abscesses that are 3.0 cm were more likely to require surgical intervention to achieve a cure (p < 0.005). Reference Rosenblum, Hoff, Norman, Edwards and Berg36
Rupture of the intracerebral abscess into the ventricular system either spontaneously or iatrogenically during a surgical procedure is associated with a case fatality rate reported between 84% and 100%. Reference Omar and Khu37,Reference Zeidman, Geisler and Olivi38 The spontaneous event is thought to result from a poorly formed abscess capsule on the ventricular wall. The mortality of intraventricular rupture has decreased in recent years with the application of surgical techniques such as intraventricular lavage akin to infective hydrocephalus Reference Zeidman, Geisler and Olivi38,Reference Qin, Liang and Xu39 and broader-spectrum antibiotics that can cross the blood–brain barrier. In this survey, many respondents selected a maximally invasive surgical approach to the management of an intracerebral abscess with imaging suggestive of intraventricular rupture (Figure 7B).
We identified little discordance between the pediatric and adult trained clinicians in the management of intracerebral abscesses. In a recent review of pediatric brain abscesses, Mameli et al. outline recommendations for surgical aspiration versus excision of intracerebral abscesses in children. Reference Mameli, Genoni, Madia, Doneda, Penagini and Zuccotti21 Specifically, these authors recommend aspiration for abscesses >2.5 cm, multiple and deep-seated abscesses that may be in eloquent locations and at high risk of complication with excision. Abscesses in children may be considered for surgical excision if located in the posterior fossa, there are multilobulated lesions, or result from a prior cranial trauma.
In the present survey study, given the small number of pediatric neurosurgeon respondents, we were unable to identify differences in pediatric compared to adult practice in the management of intracerebral abscesses. Additionally, despite a long data collection period, the response rate was low including some large high-volume centers, therefore the generalizability of the findings to the practices across the country are limited. Recall bias may have influenced respondents estimates of the number of intracerebral abscesses seen in consultation per month.
This survey demonstrated heterogeneity in the medical and surgical management of primary, recurrent, and multiple brain abscesses. No standardized practices have been proposed or adopted by the Canadian neurosurgical community. These results highlight the clinical benefit of the development of evidence-based national clinical guidelines.
To view supplementary material for this article, please visit https://doi.org/10.1017/cjn.2022.299.
The authors would like to acknowledge Donna Irvin from the CNSS who helped to disseminate the survey to the CNSS members and all the surgeons and trainees who participated in this project.
Conflicts of Interest
The authors have no conflicts of interest to disclose.
Statement of Authorship
MKS and KR conceptualized the research question. MKS, MR, SH, TD, MM, JC, MR, DB, ME, AC, A-M-L, CG, AP, MH, AW, and LE extracted that data from the databases. MKS, MA, and FF analyzed and interpreted the data. MKS wrote the manuscript with significant revisions contributed by MR and TD, and FF. KR, SC, and FF supervised the study. All authors reviewed the results and commented on the manuscript.