Abscess formation within a cerebellar metastasis: Case report and literature review

Intracranial infections: lessons learned from 52 surgically treated cases

OBJECTIVE

Intracranial infections are serious and life-threatening health problems. They may present as subdural empyemas or intracerebral abscesses. Surgical drainage and subsequent antibiotic treatment is the main technique for a satisfactory clinical outcome. The aims of this study were to present a 10-year intracranial infection series and discuss the surgical characteristics in the light of literature.

METHODS

Fifty-two patients with intracranial infection underwent surgical treatment between 2008 and 2018. Eleven patients were female and 41 patients were male. The mean age was 40.46 years (range 10-75 years). Eighteen patients had intracerebral abscesses, and 34 had subdural empyemas. All patients underwent surgical treatment as well as an antibiotic regimen.

RESULTS

No etiological agent was isolated in 29 (56%) cases. Bacterial agents were detected in 20 cases, while fungi were observed in 3 cases. Staphylococci species were the most common agents and were isolated in 8 (15%) cases. Endoscopic aspiration was performed in 3 cases, while surgical drainage and capsule resection via craniotomy was performed in 49 cases. An associated intracranial tumor was diagnosed in 2 patients with brain abscesses. Four (8%) patients died despite surgical and medical treatments.

CONCLUSIONS

Surgical treatment via craniotomy is an older method, but it is still the best to treat the intracranial infections not only for decompression of the brain but also to attain an accurate diagnosis. The abscess wall should always be histologically examined after surgery to rule out any intracranial tumor.

Abscess Formation in Metastatic Brain Tumor with History of Immune Checkpoint Inhibitor: A Case Report

We present the case of a 68-year-old man with brain metastasis from lung cancer and a history of immune checkpoint inhibitor administration, with overlapping abscess within the metastatic lesion. He initially received antibiotic treatment under a diagnosis of brain abscess because of a hyper-intense area on diffusion-weighted imaging inside the gadolinium-enhanced wall. The size of the enhanced lesion did not change much, but the extent of perifocal edema decreased after antibiotic treatment. After 2–4 months, the lesion gradually enlarged, and imaging characteristics changed from single cyst to multiple cysts. Surgical resection was performed and pathological examination revealed the lesion as metastasis from the lung tumor. Smear preparation of the tumor contents detected Gram-positive bacilli, confirming the dual pathology of metastasis and brain abscess. Discussing the pathogenesis, we speculated that therapy with durvalumab (MEDI4736), an anti-PD-L1 antibody, induced immune status modification including immunosuppressive regulation, which might have promoted abscess formation.

Abscess within a Glioblastoma: Mimicking a Matryoshka Doll

BACKGROUND

Abscess coexisting within a brain tumor is rare. Case reports in the literature primarily consist of sellar pathology and parenchymal lesions, including meningioma, glioma, and metastases. We report a case of glioblastoma with an intratumoral abscess in a middle-aged patient with no prior invasive procedure or systemic focus of infection.

CASE DESCRIPTION

A 45-year-old woman presented with new-onset generalized seizures and rapidly progressive left hemiparesis. Imaging showed a right frontal necrotic lesion with a peripherally enhancing wall and solid component posteriorly. There was no diffusion restriction within the lesion. She was afebrile, and there was no systemic focus of infection. With provisional diagnosis of malignant glioma, she underwent surgical resection of the lesion. A differential diagnosis of abscess was considered preoperatively because of the rapid increase in size of the lesion. At surgery, there was a pus-filled cavity with a few areas of grayish, soft, flimsy wall and thrombosed veins. This raised a strong suspicion of a coexisting abscess within a malignant glioma, which was confirmed by histopathologic and microbiologic examination.

CONCLUSIONS

It is important for neurosurgeons to be aware of this rare entity. The treatment protocol remains controversial and is primarily guided by expert opinion. It is important to aggressively treat the patient with antibiotics followed by adjuvant therapy for malignancy. The timing and administration of adjuvant therapy are unclear. We suggest a delay of chemotherapy until at least 4 weeks of therapy with sensitive antibiotics.

Tubo-Ovarian Abscess (with/without Pseudotumor Area) Mimicking Ovarian Malignancy: Role of Diffusion-Weighted MR Imaging with Apparent Diffusion Coefficient Values

Objective

To assess the added value of diffusion-weighted magnetic resonance imaging (DWI) with apparent diffusion coefficient (ADC) values compared to MRI, for characterizing the tubo-ovarian abscesses (TOA) mimicking ovarian malignancy.

Materials and Methods

Patients with TOA (or ovarian abscess alone; n = 34) or ovarian malignancy (n = 35) who underwent DWI and MRI were retrospectively reviewed. The signal intensity of cystic and solid component of TOAs and ovarian malignant tumors on DWI and the corresponding ADC values were evaluated, as well as clinical characteristics, morphological features, MRI findings were comparatively analyzed. Receiver operating characteristic (ROC) curve analysis based on logistic regression was applied to identify different imaging characteristics between the two patient groups and assess the predictive value of combination diagnosis with area under the curve (AUC) analysis.

Results

The mean ADC value of the cystic component in TOA was significantly lower than in malignant tumors (1.04 ± 0 .41 × 10⁻³ mm²/s vs. 2.42 ± 0.38 × 10⁻³ mm²/s; p < 0.001). The mean ADC value of the enhanced solid component in 26 TOAs was 1.43 ± 0.16×10⁻³mm²/s, and 46.2% (12 TOAs; pseudotumor areas) showed significantly higher signal intensity on DW-MRI than in ovarian malignancy (mean ADC value 1.44 ± 0.20×10⁻³ mm²/s vs.1.18 ± 0.36 × 10⁻³ mm²/s; p = 0.043). The combination diagnosis of ADC value and dilated tubal structure achieved the best AUC of 0.996. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of MRI vs. DWI with ADC values for predicting TOA were 47.1%, 91.4%, 84.2%, 64%, and 69.6% vs. 100%, 97.1%, 97.1%, 100%, and 98.6%, respectively.

Conclusions

DW-MRI is superior to MRI in the assessment of TOA mimicking ovarian malignancy, and the ADC values aid in discriminating the pseudotumor area of TOA from the solid portion of ovarian malignancy.

Development of Glioblastoma after Treatment of Brain Abscess

OBJECTIVE

Abscess formation within a glioblastoma has been reported rarely. In the few reported cases, after aspiration to treat a presumed abscess, lesions recurred over a short period and, consequently, glioblastoma was recognized. We present a case of a glioblastoma that developed 1.5 years after successful treatment of a brain abscess. A latency of 1.5 years before symptom development seems overly long, even if the glioblastoma was present at the time of the initial brain abscess. Hence, we consider this a possible de novo glioblastoma arising from glial scar tissue. We also discuss possible mechanisms underlying malignant transformation.

CASE DESCRIPTION

A 78-year-old man was admitted to our hospital with progressive gait disturbance caused by a brain abscess. Aspiration of the cyst and systematic antibiotic therapy cured the abscess. However, 1.5 years later, the patient presented to our hospital with generalized convulsions due to recurrence of the cystic lesion. He underwent craniotomy for removal of the cystic lesion, which was found to be a glioblastoma rather than a recurrent brain abscess. Glial scar tissue was detected in the cyst wall.

CONCLUSIONS

Development of glioblastoma after treatment of a brain abscess is rare; the pathogenesis is open to speculation. Based on the clinical course, the pathologic findings, and comparison with previous reports, de novo glioblastoma arising from glial scar tissue may be the most likely explanation of the current case. If so, to our knowledge, this is the first report of this condition.