Brain abscess by Streptococcus anginosus because of chronic pansinusitis: a case report

Introduction

Streptococcus anginosus species is the principal member of the Streptococcus anginosus group, a subgroup of viridans streptococci previously described as Streptococcus milleri group. Based on biological similarities and a predisposition for causing similar infections, two other species are also considered part of Streptococcus anginosus group: Streptococcus constellatus and Streptococcus intermedius. All three are commensal bacteria found on the mucosal membranes of the oropharynx and nasopharynx, the gastrointestinal system, and the urogenital system (1). When pathogenic, they are often associated with the formation of abscesses wherever infection occurs and, to a lesser extent, endocarditis. Literature reports a predominance of Streptococcus intermedius responsible of the formation of a brain abscess (2,3). Infections are often polymicrobial and involve various anaerobic bacteria. They are generally susceptible to β-lactam antibiotics. More than 98% of the strains would be considered fully susceptible to penicillin G (4). This case describes an exceptional manifestation of an invasive Streptococcus anginosus infection with a brain abscess, arisen from a chronic pansinusitis in an immunocompetent patient, and necessitating multiple surgical drainages and long-term treatment with intravenous antibiotics. We present this case in accordance with the CARE reporting checklist (available at https://jeccm.amegroups.com/article/view/10.21037/jeccm-24-46/rc).

Case presentation

A 21-year-old male was referred by the general practitioner to the emergency department because of persisting headache. The complaints started a month before, but improved for a period after taking over the counter medication against sinusitis. A week before presentation the headache started again progressively, associated with nausea, vomitus, and progressive fatigue. A day before presenting at the emergency department the complaints were even more progressively with difficulties to open the left eye.

Past medical history of this man was limited with known pansinusitis since 2014, no known daily medication or no risk factors causing immunosuppression were present for this patient.

At presentation in the emergency department vitals were stable, no fever was measured. The man was weak and in need of a wheelchair. Physical examination showed abnormalities in the neurological evaluation. We marked mydriatic left eye and ptosis of the left eyelid. Eye movement tests were divergent, adduction and elevation of the left eye was impossible.

Blood was drawn and revealed: hemoglobin 13.9 g/dL (normal range, 13.1–17.3 g/dL), leukocyte count 10.9×10³/µL [normal range, (3.6–10.9)×10³/µL], neutrophils 76%, C-reactive protein 10.4 mg/dL (normal range, <5.0 mg/dL). Blood cultures were taken, but showed no significant growth of bacteria. A cranial computed tomography (CT) with and without contrast was performed, which showed a multifocal, peripheral coloring and space-consuming mass in the left frontal lobe with extensive perilesional edema, and concomitant mass-effect at the supratentorial ventricular system. The scan also showed pansinusitis, with bilateral breakthrough of the posterior wall of the frontal sinus. In the differential diagnosis an infectious process from the sinus cavities, or a tumoral mass from the brain parenchyma (e.g., glioblastoma) was considered (Figure 1).

Figure 1 MRI brain results. (A,B) T2-TSE image showing a multifocal mass in the left frontal lobe with extensive perilesional edema and pansinusitis with close contact between the mass and the frontal sinus. (C) Diffusion image showing central diffusion restriction of the mass with extensive perilesional edema. MRI, magnetic resonance imaging; TSE, turbo spin-echo.

Empiric antibiotics were already started at the emergency department, ceftriaxone 2 g twice a day and metronidazole 500 mg three times a day, in combination with steroids (methylprednisolon 40 mg three times a day). He was subsequently admitted to the intensive care department where we arranged an urgent brain magnetic resonance imaging (MRI) (Figure 1). While not completely diagnostic, the presence of central diffusion restriction of the mass fit best with an infectious abscess.

We consulted our neurology, ophthalmology, ear, nose, and throat (ENT), neurosurgery, and microbiology department. The neurologist suggested to start the patient on levetiracetam, for epilepsy prevention. The ophthalmologist did a full examination where they withheld bilaterally papillary edema and paresis of the left trochlear nerve. The ENT physician performed a sinus cavity punction with drainage of purulent fluid. Cultures of this fluid showed growth of Staphylococcus epidermidis (two out of four different cultures), methicillin-susceptible Staphylococcus aureus (MSSA) (two out of four different cultures), Streptococcus salivarius, and Streptococcus oralis. The neurosurgeons planned a stereotactic punction and drainage of the abscess for further diagnostics, which took place at day four of hospitalization. Cultures of the drainages gave us the diagnosis of an infection with Streptococcus anginosus species, which the microbiologist identified with the MaldiTof-MS method of Bruker with a score of 2.06. So, the presumption of an intraparenchymal brain abscess was confirmed. The empiric antibiotic therapy with ceftriaxone and metronidazole was continued, and vancomycin was added for 14 days.

Meanwhile, neurologic symptoms persisted and brain CT controls showed a slight increase in abscess dimensions, so two new stereotactic punctures and drainages were performed (on days 8 and 22 of hospitalization). In combination with persistent intravenous antibiotics, we eventually saw improvement in symptoms and brain CT controls. It was on day 43 the neurosurgeons proceeded to do a trepanation with closure of the frontal sinus defect.

On day 50, antibiotic therapy was stopped and the patient was discharged from the hospital. On that point, the follow-up CT showed persistent regression of the mass together with decrease in perilesional edema, but was still not completely disappeared. He followed an outpatient rehabilitation program and came on follow-up consultations with the ophthalmologist and the neurologist. Ten weeks after discharge we saw a promising neuropsychologic examination without any cognitive dysfunction. Also, the paresis of the left trochlear nerve recovered. The papillary edema remained to a lesser extent. Eventually also at the brain CT control, we saw regression of the known mass.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent for publication of this case report and accompanying images was not obtained from the patient or the relatives after all possible attempts were made.

Discussion

We described a case of a young man without comorbidities, with an intraparenchymal brain abscess because of an invasive Streptococcus anginosus infection. According to literature, the incidence of an invasive Streptococcus anginosus bacteremia is around 0.93 per 100,000 population per year (5). Further information on the occurrence of a brain abscess is only known in case reports, but no general numbers are available. A brain abscess can develop due to the direct spread of bacteria, as seen in a sinusitis, otitis media, or mastoiditis, where the adjacent tissues are affected. Another mechanism is the hematogenous spread of bacteria from an extra-cranial infection (2). Predisposing factors for invasive Streptococcus anginosus infections include being immunocompromised, penetrating trauma, neurosurgical operation, bad oral/dental hygiene, and severe sinusitis (4).

The diagnosis of intraparenchymal brain abscesses still remains difficult. Presenting symptoms of headache, vomiting, fatigue of focal neurological symptoms are mostly tenuous. Possible diagnosis for an immunocompetent patient would be less invasive (example: sinusitis, migraine, etc.). Initial treatment would be with over the counter medication. As described in the article from Oyama et al., half of the patients in their population were diagnosed inaccurately in the initial stage, and it took 7.2 days to achieve the final diagnosis of brain abscess for the misdiagnosed patients. In addition, inflammatory markers such as leukocyte count and C-reactive protein can stay relative low and this makes the initial diagnosis even more difficult. The reason for these low values can be found in the absence of associated meningitis or ventriculitis (6).

The virulence factors of invasive Streptococcus anginosus and risk of refractory infections can complicate the individual treatment and pose a challenge to the treating physician (7). In recent years, an increased prevalence of these invasive infections has been described. It is not clear whether this increased prevalence is only due to better microbiological testing, a higher vigilance for this pathogen or a concrete increase of disease burden (8).

As described in the introduction, penicillin G should give enough coverage because of the low probability of antibiotic resistance (9). We chose in this case for a wider antibiotic coverage with ceftriaxone, temporarily vancomycin, and metronidazole because of the initial unclear presentation of the case and the presence of a polymicrobial infection with other pathogens from the sinus cavity puncture. Noticeable was the absence of Streptococcus anginosus group pathogen in the sinus cavity puncture cultures. A possible explanation is the difficulty to differentiate in a polymicrobial sample the role as normal commensal flora or a more pathogenic bacteria.

The recommended treatment consists of long-term intravenous antibiotics, in combination with surgical interventions. This pathogen often requires more aggressive surgical interventions and longer lasting antibiotic treatment in comparison with some other bacteria (1,9). Literature suggests to continue the intravenous antibiotics for at least 6 to 8 weeks, and longer if necessary based on clinical presentation and radiographic follow-up (10). Like the patient in this case, 50-day antibiotic treatment was administered in combination with three stereotactic punctures and drainages, followed by a reconstruction of the frontal sinus defect. It was because of this invasive and multidisciplinary treatment course that this patient made a promising recovery.

There is one study of Kameda-Smith et al. in 2022 who described the surgical approach of brain abscesses, but it was not specified for the different pathogens. They found no significant difference in outcome of the patients if they compared the surgical excision with the needle aspiration (11). Our neurosurgeon chose the method of needle aspiration because the less invasive character of this approach and their expertise.

We advocate to be aware for this rare infection in immunocompetent patients, and to put this possible diagnosis higher in your differential diagnosis when you encounter a patient with a new onset of headache and other associated but mild symptoms. Furthermore, we recommend early and invasive therapy with long lasting antibiotic treatment and surgical drainage of the abscess.

Conclusions

This case represented an intraparenchymal brain abscess in a generally healthy young man, most likely originated from the direct spread from a chronic pansinusitis. It is a rare infection in immunocompetent patients, but it is important to be vigilant for this disease presentation. The case renders the difficulties in diagnoses with often tenuous or mild symptoms and relative low inflammatory markers. However, it emphasizes the importance of adequate imaging and long-lasting antibiotic treatment for at least 6 weeks, along with the necessity of (sometimes multiple) surgical interventions.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://jeccm.amegroups.com/article/view/10.21037/jeccm-24-46/rc

Peer Review File: Available at https://jeccm.amegroups.com/article/view/10.21037/jeccm-24-46/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jeccm.amegroups.com/article/view/10.21037/jeccm-24-46/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent for publication of this case report and accompanying images was not obtained from the patient or the relatives after all possible attempts were made.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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