Introduction
India is recently witnessing a surge in cases of melioidosis, usually considered an
endemic disease and an important public health problem in Southeast Asia and Northern
Australia.[1] It is caused by Burkholderia pseudomallei, an environmental saprophytic gram-negative bacterium, which predominantly affects
persons with diabetes mellitus and various other underlying predispositions such as
heavy alcohol intake, chronic pulmonary disease, chronic renal disease, glucocorticoid
therapy, and malignancy. The clinical manifestations range from a mild subacute disease
with localized lesions to a fulminant septicemic form. Involvement of central nervous
system (CNS) is an unusual event. We report a case of intracranial melioidosis manifested
as a brain abscess in an occupationally unexposed patient, who had an excellent outcome
owing to appropriate neurosurgical intervention, accurate etiological identification,
and effective antibiotic therapy.
Case Report
A 48-year-old lady was presented to the emergency room with a history of headache
for the last 10 days, holocranial in nature, associated with episodes of vomiting
followed by altered sensorium for last 2 days. She was a known diabetic and hypertensive
on irregular medication. She was drowsy on examination with right hemiparesis. Her
noncontrast computed tomography head, upon admission, showed a hypodense space-occupying
lesion present in left parietal region with significant perilesional edema, and midline
shift toward right present. Extradural collection was present in the left parietal
region along with developing infarct in the left posterior cerebral artery territory.
Contrast-enhanced magnetic resonance imaging done outside showed T1 hypointense, T2
hyperintense, ring enhancing lesion present in left parietal region with restriction
of diffusion suggestive of abscess. Extradural collection was present over the left
parietal region with contrast enhancement of the dura suggestive of extradural empyema.
In view of her poor sensorium, she was immediately intubated and taken up for urgent
surgery. All the three samples (intraparenchymal pus, extradural collection, and excised
dura) yielded pure growth of B. pseudomallei sensitive to ceftazidime, meropenem, and trimethoprim–sulfamethoxazole. Postoperative
imaging ([Fig. 1]) showed complete evacuation of the abscess cavity. Her echocardiography, blood culture,
and other systemic evaluation did not reveal any infective foci. The patient recovered
well from surgery and improved in neurology at 1-year follow-up.
Discussion
B. pseudomallei, the causative organism of melioidosis, is a gram negative, opportunistic, facultative
intracellular, motile, saprophytic bacterium, endemic to South and Southeast Asia,
China, and Northern Australia.[2] Melioidosis was first identified in Rangoon in 1911 by Alfred Whitmore, a British
doctor and his assistant, CS Krishnaswami.[3] Infection by B. pseudomallei can be acute, chronic, or latent, although in immunocompetent individuals it most
commonly presents as a subclinical infection. Only those patients who are clinically
symptomatic are considered to have melioidosis.[3] Routes of infection of B. pseudomallei are through ingestion, inhalation, and skin penetration. Nosocomial infections have
also been reported to occur through contaminated wound irrigation fluid, antiseptics,
and hand wash.[4]
[5] The average incubation period of period of melioidosis is 9 days.[6] CNS is rare, with 1.5 to 5% cases of melioidosis having a neurological involvement.[1] The usual presentation of melioidosis is pneumonia.[3] Diabetes mellitus is the most significant risk factor for the development of melioidosis,
conferring a 12-fold higher risk. Excess alcohol use, liver disease, prolonged steroid
use, and immunosuppression are other risk factors.[2]
Wongwangdee and Linasmita in their review of CNS melioidosis found that the median
age of the affected patients was 40 years, the youngest being 10 days old and the
oldest aged 75 years.[2] Most of the patients identified in their review were acute melioidosis. Encephalomyelitis
was the most common presentation followed by cerebral abscess. Patients with cerebral
abscess presented with fever, unilateral weakness, and altered sensorium. Fifty-six
percent patients had neck stiffness and 40% patients developed seizures. Cranial nerve
palsies were reported in 48% cases with facial palsy being the most common. Frontal
and parietal lobe, cerebellar hemispheres, and brainstem are the most common sites
affected by CNS melioidosis.
The diagnosis of cerebral abscess due to B. pseudomallei can be made by imaging followed by isolation of the organism. Pus from the abscess,
brain tissue, or cerebrospinal fluid (CSF) can be used for culture. Routine examination
of the CSF shows mononuclear pleocytosis with increased protein and decreased glucose
levels. Blood culture can also grow B. pseudomallei suggestive of hematogenous spread. If there is an overlying infection of the cranial
bones or the scalp, these can also be used for culture. Serology with indirect hemagglutinin
assay is not reliable enough for clinical practice.[3]
Medical management of B. pseudomallei includes an intensive phase of 8 weeks and an eradication phase of 6 months. Guidelines
recommend ceftazidime and meropenem to be the drug of choice for intensive phase and
trimethoprim–sulfamethoxazole for eradication therapy.[7] Surgical management is warranted to establish the diagnosis and to relieve the mass
effect. No definite guidelines are available regarding the choice of surgical strategy
for cerebral abscess due to melioidosis. Available options are burr hole and tapping
of abscess with stereotaxy if available for surgical drainage of the abscess with
excision. The surgical strategy must be decided on a case-by-case basis by the treating
surgeon.
Conclusion
B. pseudomallei causing cerebral abscess is a rare pathology and may pose a diagnostic dilemma. Appropriate
and rapid diagnosis along with treatment should be initiated as this presentation
is associated with a high mortality (25%).[8]
Fig. 1 (A) Preoperative computed tomography showing hypodense space-occupying lesion present
in the left parietal region with significant perilesional edema and midline shift
toward left. (B) Preoperative computed tomography brain showing developing infarct in left posterior
cerebral artery territory. (C) Preoperative magnetic resonance imaging brain showing ring enhancing lesion present
in the left parietal region. (D) Preoperative contrast-enhanced magnetic resonance imaging brain showing presence
of extradural collection in left parietal region with enhancement of the dura. (E) Preoperative diffusion-weighted image showing presence of diffusion restriction
within the lesion. (F) Postoperative computed tomography brain showing complete evacuation of the abscess
cavity. Parietal craniectomy defect present.
