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|LETTER TO EDITOR
|Year : 2011 | Volume
| Issue : 5 | Page : 779-782
Nocardial brain abscess in an immunocompetent individual
Akshay Patil1, Ajith Cherian2, Thomas Iype2, P Sandeep2
1 Department of Neurosurgery, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India
2 Department of Neurology, Government Medical College, Trivandrum, Kerala, India
|Date of Submission||21-Jun-2011|
|Date of Decision||21-Jun-2011|
|Date of Acceptance||29-Jun-2011|
|Date of Web Publication||22-Oct-2011|
Department of Neurology, Government Medical College, Trivandrum, Kerala
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Patil A, Cherian A, Iype T, Sandeep P. Nocardial brain abscess in an immunocompetent individual. Neurol India 2011;59:779-82
Cerebral nocardiosis is uncommon, accounting for only 2% of all cerebral abscesses.  Nocardia asteroides , is responsible for up to 86% of nocardial infections.  Cerebral nocardiosis is associated with significant morbidity and mortality (34%), highest with brain abscess. Nocardiosis is often an opportunistic infection in an immunocompromised individual. We report a case of brain abscess due to Nocardia brasiliensis in an immunocompetent individual, which required repeated surgeries.
A 53-year-old male, with no preceding medical illness, presented with complaints of headache, visual disturbances, and generalized seizures of 3 months' duration. Examination showed bilateral papilledema and left homonymous hemianopia. Brain imaging with contrast computed tomography (CT) and contrast magnetic resonance imaging (MRI) revealed a 2.5 × 2.2 × 2.1-cm ring-enhancing lesion in the right occipital area, with significant perilesional edema [Figure 1]a-f. CT of chest and abdomen revealed a fibrotic band lesion in the apical segment of the left lung [Figure 1]h. The patient underwent right parieto-occipital craniotomy and abscess excision [Figure 1]g. Pus showed gram-positive bacilli with faint AFB staining, while culture grew N brasiliensis , sensitive to linezolid, trimethoprim/sulfamethoxazole (TMP/SMZ), imipenem, rifampin, and fluoroquinolone. The patient was initially followed up on linezolid, but 4 months later he presented with headache. Evaluation with contrast MRI showed a recurrent thick-walled right occipital abscess with a small epidural collection [Figure 2] a-f. He underwent re-exploration, and the lesion was excised in toto. Histopathology showed acute exacerbation of chronic inflammation.
|Figure 1: (a) axial plain CT scan showing hypodense lesion in the right occipital region, which shows ring enhancement on contrast (b). Axial MRI T1-weighted sequences showing hypointense lesion (c) with surrounding edema; this is appreciated better on T2-weighted sequences (d). The hypointense wall shows contrast enhancement (e), and conglomerate lesions are seen on coronal sections (f). The first postoperative contrast CT scan shows lack of ring enhancement (g). CT scan chest shows the healed left apical lung lesion (h).|
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|Figure 2: (a) Axial contrast CT scan prior to the second surgery showing hypodense ring-enhancing lesion in the right occipital region, suggesting recurrence. Axial MRI postcontrast T1-weighted sequences showing hypointense lesion (b) with ring enhancement; conglomerate lesions are seen on sagittal sections (c), along with subdural and extradural collection. Diffusion-weighted images (d) showing restricted diffusion, suggesting abscess, while apparent diffusion coefficient images (e) shows hypointensity. Magnetic resonance spectroscopy showed lipid lactate peak at 1.3, suggesting abscess (f).|
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The patient has now completed 9 months of follow-up after the second surgery. He was on two anticonvulsants, TMP/SMZ, and rifampin when he developed TMP/SMZ-induced leukopenia that required drug withdrawal. Follow-up imaging showed no recurrence [Figure 3] a-c. At present, the patient has residual hemianopia but is otherwise symptom free.
|Figure 3: (a) Diffusion-weighted images showing no restricted diffusion, while apparent diffusion coefficient images (b) shows hyperintensity, suggesting good abscess clearance. Axial MRI postcontrast T1-weighted sequences showing lack of enhancement, which favors a good outcome (c)|
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Nocardia spp. infection is acquired by inhalation of airborne bacteria from environmental sources and the lung is the commonest site of initial infection.  From India reports are scanty, possibly as a result of underreporting and lack of awareness. , The hallmark of nocardial lesions is abscess formation, and in the central nervous system (CNS) these lesions often mimic brain tumors.  Hematogenous dissemination from either the primary pulmonary or cutaneous infection can result in disease in virtually any part of the body, but the brain and soft tissues are most commonly affected. Unlike primary pulmonary and cutaneous infections, which may be self-limiting, lesions of disseminated nocardiosis progress unless treated.  On CT scan, a nocardial lesion is evident as a hypodense area that is predominantly supratentorial (in 57% of cases).  The abscess usually consists of a multiloculated structure resulting from coalescence of multiple daughter abscesses. Nocardiosis should be considered as a differential diagnosis if brain abscesses heal less rapidly or less completely than expected with standard empiric therapy. Excision of the abscess and antibiotic therapy results in rapid improvement and successful resolution of symptoms. Aspiration of the abscess, in combination with antibiotic therapy, may be tried as the first approach in immunosuppressed patients if poor wound healing is of concern. Patients may often require more than one surgical intervention for complete removal, as in our patient. The reported mortality in CNS nocardiosis varies, being 24% in patients treated with craniotomy and excision and 50% in patients treated with aspiration alone.
Our patient is unique in that he was an immunocompetent individual and the species isolated was N brasiliensis , an extremely uncommon organism even in Central and South America, which are endemic for nocardiosis. In patients with multiloculated ring-enhancing lesions, nocardiosis should be suspected even in nonendemic regions.
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[Figure 1], [Figure 2], [Figure 3]
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