Keywords
brain tumor - meningioma - abscess
Introduction
Intra- and parasellar tumors are the most common intracranial neoplasms to harbor
abscess because of direct extension of microbial flora from paranasal sinuses.[1]
[2] Glioblastoma, astrocytoma (high and low grade), ependymoma, and metastatic lesions
have also been reported to harbor abscesses within them. Only nine cases of intracranial
meningioma associated with brain abscess have been reported in literature so far,
with intra- and peritumoral location of abscess being rare.[3]
[4]
[5] We report yet another case; however, a source of infection could not be identified
in our patient.
Case Description
A 56-year-old man with well-controlled diabetes mellitus was evaluated for headache
associated with vomiting and found to have a dural-based, contrast-enhancing lesion
with perilesional edema located in relation to middle one-third of the falx on the
left side. He refused surgery and presented 7 months later with headache and clumsiness
of the right upper limb. Repeat imaging showed increase in the size of the lesion
with change in the pattern of contrast enhancement in the area adjacent to the original
lesion ([Fig. 1]). Differential diagnoses of meningioma with malignant transformation, metastasis,
and tuberculoma were considered.
Fig. 1 MRI T1 contrast (first row) and CT of the brain with contrast (second row) done 7
months apart. There is a change in the size, shape, perilesional edema, and pattern
of contrast enhancement. The original lesion is thick walled with areas of calcification
and the newer lesions are thin walled but incontiguous with the first one.
After obtaining consent, a left temporoparietal craniotomy and excision of the lesion
was performed. Perioperatively, the dural-based lesion was vascular with a thick capsule
and pus in the center of the lesion that was communicating with the peritumoral abscess
([Fig. 2A]). Gross total excision of the lesion with dural attachment was performed. Histopathology
was suggestive of meningioma ([Fig. 2B–D]). Escherichia coli was isolated from the purulent material. The patient had an uneventful recovery and
was treated with antibiotics for 4 weeks.
Fig. 2 (A) Intraoperative photograph showing abscess within the tumor (arrow head). (B) H&E stain showing neoplastic tissue composed of fascicles of cells with oval to
spindled nuclei and psammoma body (arrow). (C) Neoplastic cells are positive for epithelial membrane antigen on immunohistochemistry.
(D) Dense infiltration by lymphocytes, plasma cells, and histiocytes with focal necrosis
also noted in the wall of the tumor. H&E stain, hematoxylin and eosin stain.
Discussion
The vascularity of meningioma, location outside the blood-brain barrier, and the rich
nutritive environment provided by tumor cells make meningiomas susceptible to abscess
formation, especially in the presence of foci of infection elsewhere in the body.[5]
[6]
[7]
[8] The vascular pattern of the meningioma is such that the feeding artery supplies
the core of the meningioma and the branches supply the periphery facilitating entrapment
of pathogen in the center of the tumor. In the presence of additional venous compression
by tumor, especially in the parasagittal location, the stagnation of blood and pathogen
in the center of the tumor is facilitated. Peritumoral abscess can be explained by
the seedling of pathogens during bacteremia at the sites of blood-brain barrier breakdown
induced by tumor response.[9] The patient probably had an untreated, asymptomatic urinary tract infection in the
past, which could have precipitated low grade bacteremia, thereby predisposing to
intra and peritumoral abscess formation.
1H-magnetic resonance spectroscopy (MRS), diffusion-weighted imaging (DWI), dynamic
susceptibility contrast perfusion magnetic resonance imaging (MRI), and 99mTc-labeled
sulesomab (LeukoScan, Immunomedics, Inc.) are investigations that can aid in differentiating
brain abscesses from cystic or necrotic tumors. Lactate (1.3 ppm), acetate (1.92 ppm),
and succinate (2.4 ppm) peaks noted on MRS in patients with brain abscess presumably
originate from enhanced glycolysis and fermentation of microorganisms. Valine, isoleucine,
and leucine (0.9 ppm) peaks in spectroscopic imaging of abscess result from end products
of proteolysis by enzymes released by neutrophils in pus.[10] These peaks also disappear following effective antibiotic therapy and hence, can
be used to monitor response to therapy. The spectral metabolite pattern of lactate,
amino acids, alanine, and acetate, with or without succinate, shows an abscess caused
by obligate anaerobes or a mixture of obligate and facultative anaerobes while that
of lactate and amino acids reveals an abscess caused by obligate aerobes or facultative
anaerobes. Presence of lactate alone shows small and/or treated abscesses.[11] Diffusion and apparent diffusion coefficient (ADC) maps are more accurate than MRS
in differentiating abscesses from cystic or necrotic tumors. Pyogenic abscesses have
high signal on DWI with ADC ratios between 0.45 and 0.8. Cystic and necrotic portion
of tumors have low signal on DWI and ADC values between 15 and 18.[10]
[12] Measurement of regional cerebral blood volume (rCBV) by dynamic susceptibility contrast
(T2 weighted) MRI hemodynamic imaging reveals high rCBV for high-grade tumors and
low rCBV for abscesses compared with normal white matter tracts.[13] Sulesomab is a monoclonal antibody that binds to antigen present on the surface
of activated neutrophils present in the abscess cavity. Absence of tracer uptake in
brain lesion on 99mTc-labeled sulesomab (LeukoScan) rules out infection with a high
degree of certainty. However, false-negative result may be obtained if the patient
is on steroid therapy.[14]
Meningioma with abscess should be considered in the differential diagnosis of dural-based
lesions with significant perilesional edema, especially in those with a history of
systemic infection. Preoperative evaluation in such patients should include echocardiography,
ultrasound of the abdomen and pelvis, dental screening, and, in symptomatic patients,
urine culture and ENT (ear-nose-throat) consultation for sinusitis. Radical surgery
followed by a suitable antibiotic protocol, deferring adjuvant postoperative therapy
till resolution of abscess, is associated with a favorable outcome.[14]
Note
A written informed consent was obtained from the patient for publication of this case
report and any accompanying images.
