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|Year : 2020 | Volume
| Issue : 4 | Page : 906-909
Scedosporium Apiospermum: Rare Cause of Brain Abscess in an Immunocompetent Patient
Amol Y Sudke1, Salman T Shaikh1, Chandrashekhar E Deopujari1, Asmita S Sakle2
1 Department of Neurosurgery, Bombay Hospital Institute of Medical Sciences, Mumbai, Maharashtra, India
2 Department of Microbiology, Bombay Hospital Institute of Medical Sciences, Mumbai, Maharashtra, India
|Date of Web Publication||26-Aug-2020|
Dr. Chandrashekhar E Deopujari
Room No 114, MRC Building, Bombay Hospital, 12, New Marine Lines, Mumbai - 400 020, Maharashtra
Source of Support: None, Conflict of Interest: None
Scedosporium apiospermum is a filamentous fungus causing a broad spectrum of clinical diseases especially in those who are immunocompromised. The common sites involved are lungs, skin, sinuses, eyes, bones, joints, and central nervous system (CNS). CNS is involved in invasive Scedosporiosis in the form of a cerebral abscess. An antecedent event of either near-drowning or history of some trauma is present in the majority of the cases where the patients' immune response remains intact. Prognosis is generally poor since the majority of the patients have coexistent medical morbidity. Surgical drainage followed by adjuvant antifungal, i.e., voriconazole therapy offers the best possible chance for survival in these patients. This case report discusses a rare event of brain abscess caused by S. apiospermum in an immunocompetent patient without any preceding precipitating factor.
Keywords: Brain abscess, immunocompetent, scedosporium
Key Messages: Scedosporium apiospermum is a rare cause of fungal brain abscess, more so in an immunocompetent individual. History of near-drowning and trauma must be ruled out. Treatment consists of surgical drainage followed by intravenous voriconazole therapy. Prognosis remains poor.
|How to cite this article:|
Sudke AY, Shaikh ST, Deopujari CE, Sakle AS. Scedosporium Apiospermum: Rare Cause of Brain Abscess in an Immunocompetent Patient. Neurol India 2020;68:906-9
Scedosporium family consists of two medically important species: Scedosporium apiospermum and Scedosporium prolificans, which are commonly found in soil, polluted water and sewage. The whole spectrum of infection caused by this complex is termed as Scedosporiosis. Central nervous system (CNS) infection in the form of brain abscess is more common in immunocompromised patients although they rarely occur in healthy patients as well, especially those with a history of trauma or near-drowning. The plausible hypothesis for the spread of the organism can be attributed to hypoxia, use of steroids for aspiration pneumonitis affecting the hosts' immune response, and hematogenous spread of the organism from the lungs following the near-drowning episode., Diagnosis can be challenging as many features are similar to common fungal infections such as Aspergillosis. Microbiological culture of the organism is the only investigation to differentiate it from other infections and hence is considered mandatory before proceeding with definitive medical therapy. Antifungal treatment alone in invasive Scedosporiosis provides a suboptimal response. Surgical drainage is imperative before starting drug therapy.
| » Case Presentation|| |
A 72-year-old male without any comorbidities presented with complaints of sudden onset, left-sided limb weakness for four days, and history of a generalized tonic-clonic seizure on the morning of admission. There was a history of low grade, intermittent fever for two weeks associated with mild holocranial headache, which was not associated with vomiting. There was no history of trauma or any near-drowning episode. The patient had not received any immunosuppressive drugs in the past and there was no significant history suggestive of an immunocompromised state. He was a chronic smoker with no contributory family history. On examination, he was conscious and oriented with hemiplegia present in left limbs. Haematological investigations revealed hemoglobin of 14.80 gm/dl with a total leucocyte count of 14400/cu.mm (55% neutrophils, 40% lymphocytes and 5% monocytes). No abnormalities of leucocytes were seen. Erythrocyte sedimentation rate (ESR) was 16 mm/hr. Fasting and post-prandial blood sugar were 110 and 166 gm/dl, respectively. Serological status was non-reactive. Chest X-ray was normal. Sputum sent for microbiology examination yielded no growth of any organism. Magnetic resonance imaging (MRI) brain with contrast was done. A lesion in the right parietal cortex was seen with a hypointense rim on T2-weighted image (T2WI) [Figure 1]. There was evidence of hemorrhage in the lesion as seen by the peripheral hyperintense rim on pre-contrast T1WI [Figure 2] with corresponding areas of T2 shortening on gradient recalled echo (GRE) image [Figure 3]. A predominant peripheral pattern of enhancement [Figure 4] with central restricted diffusion [Figure 5] confirmed the atypical infective nature of the disease. The possibility of atypical fungal abscess was considered as a differential diagnosis due to an increased likelihood of vascular involvement and resultant hemorrhage. Positron emission tomography-computed tomography (PET-CT) scan was done and it ruled out the remote possibility of lymphoma.
|Figure 1: MRI brain T2-weighted axial images showing an ill-defined lesion in the right parietal region with hypointense rim and perilesional edema|
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|Figure 2: MRI brain T1-weighted axial image showing a hyperintense rim around the lesion suggestive of haemorrhage|
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|Figure 4: MRI brain post-contrast axial images demonstrating rim enhancement in the solitary lesion of the right parietal lobe|
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|Figure 5: MRI brain diffusion-weighted (DWI) axial images showing restricted diffusion in the center of the lesion|
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Right parietal burr hole with drainage of abscess under navigation guidance was done. Intraoperatively, thick yellowish color pus was drained and sent for histopathological and microbiological examination. Due precautions to prevent spillage and seepage of pus intracranially was taken. A thorough normal saline wash was given. Postoperative CT brain showed mild cerebral edema with excision of the lesion. Postoperative flow cytometry and immunoglobulin study was done to assess the immune response in detail revealed no abnormality. Histopathological examination was suggestive of cerebral mycoses with a necrotising granulomatous response [Figure 6]. Gram staining of the pus revealed no organism and potassium hydroxide (KOH) smear showed fungal branching hyphae. Acid-fast bacilli (AFB) stain and Gene-Xpert test were negative. Bacteriological culture revealed no growth. On the basis of the above findings, antifungal agent voriconazole (loading dose of 6 mg/kg followed by a maintenance dose of 4 mg/kg) was started intravenously. For about three weeks postoperatively, he showed mild improvement in left-sided weakness following vigorous physiotherapy. Fungal culture report after 21 days showed growth of grayish suede-like colonies on Sabouraud's dextrose agar [Figure 7], with grayish black colonies on reverse macroscopically [Figure 8]. Microscopic examination of culture on lactophenol cotton blue mount showed branching septate hyphae with single-celled ovoid conidia typical of S. apiospermum [Figure 9]. Intravenous voriconazole (4 mg/kg) was advised to be continued for further three months, once the final culture report was ready (after 3 weeks) and the patient was discharged. Unfortunately, despite regular intake of drug therapy, the patient passed away in his hometown after two months due to sudden respiratory failure as a sequela of pulmonary embolism, which may be attributed to immobilization due to weakness.
|Figure 6: Histopathological examination demonstrating branched fungal hyphae (black arrow) with necrotising granuloma representing cerebral mycoses|
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|Figure 9: Microscopic examination showing branched septate hyphae with single-celled ovoid conidia typical of scedosporium apiospermum.|
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| » Discussion|| |
S. apiospermum is an asexual form of Pseudallescheria boydii, a fungal saprophyte found in soil, contaminated water, sewage, and animal manure. S. apiospermum causes a broad spectrum of clinical conditions in immunocompromised patients involving cutaneous and subcutaneous tissues, lungs, sinuses, brain, bones, and joints., Mycetoma of the foot is a common clinical manifestation seen due to this organism. It involves the CNS in 50% of invasive disease cases, with brain abscess being the main pathology with or without associated meningitis. The usual location of abscess is cerebral hemispheres, brainstem, cerebellum, and spinal cord causing focal neurological deficit. A major predisposing factor for CNS infection is an immunocompromised status, which includes immunosuppressive therapy, transplantation, hematological malignancy, diabetes, pneumonitis, osteomyelitis, endophthalmitis, and prosthetic valve endocarditis. Near-drowning or trauma may be the causative factor for CNS infection in immunocompetent patients. A study of 99 reported cases from 1948 to 2007 found that 44/99 (44%) of reported cases affecting the CNS occurred in an immunocompetent patient. Of these patients, 24/44 (55%) had a history of near-drowning, 10/44 (23%) were post-traumatic/iatrogenic cases and 4/44 (10%) had a history of alcohol abuse. The involvement of CNS leads to a very poor prognosis, with a known mortality rate of approximately 74%, which may be due to delay in diagnosis and the lack of effective drugs that penetrate the blood-brain barrier adequately.
S. apiospermum is diagnosed on the basis of culture and microbiological examination. As the clinical and histopathological presentations of S. apiospermum infections may coincide with other similar fungal infections, culture becomes the most useful tool for diagnosis. Real-time polymerase chain reaction-based assays allow for quick, specific, and quantitative detection of Scedosporiosis from clinical samples like blood, serum, pus, etc. As of today, there is no internationally accepted fixed protocol for the treatment of invasive Scedosporiosis.
Medical management consists predominantly of voriconazole, long considered as the drug of choice in this disease due to its better penetration of the blood-brain barrier and a more potent responsein vitro against S. apiospermum. Lack of available data favoring the use of posaconazole against S. apiospermum makes this drug a second choice behind voriconazole. Troke et al. studied the efficacy of voriconazole in 107 patients with Scedosporiosis and reported a successful therapeutic response of 57%, which included those with complete or partial response to therapy. CNS involvement of the organism was associated with the worst outcome with an overall response of 43%. Invasive nature of the organism, poor response to therapy, and the persistently high mortality rates has led to wide research on the efficacy of combination drug therapy. There have been reports favoring the use of voriconazole and terbinafine,, and voriconazole or amphotericin B combined with an echinocandin. However, research on a larger scale is needed before implementing a combination regime in current practice as no literature yet has conclusively contributed towards changing the preferred regime.
Surgical drainage of the abscess along with postoperative voriconazole therapy has been recommended traditionally. Mortality rates vary from approximately 30% in those patients of S. apiospermum cerebral abscess being treated by surgical drainage plus medical therapy to 74% in those treated with antifungals alone.
| » Conclusion|| |
S. apiospermum causing brain abscess in an immunocompetent patient without any preceding event viz. drowning or trauma is a rare occurrence. Diagnosing it on microbiological cultures is imperative before proceeding with appropriate antifungal therapy. Surgical drainage removes the foci of infection, helps in obtaining a specimen for culture, and relieves the mass effect if present. This, along with adjuvant antifungal therapy with voriconazole for approximately 8 to 12 weeks, is the recommended line of treatment. A compromised immune response coupled with the widespread nature of the disease leads to a poor response to therapy. Prognosis depends upon the immune status of the patient and research efforts are ongoing for studying the efficacy of combination antifungal drug therapy. Possibility of fungal infection must be ruled out, even in an otherwise healthy patient presenting with brain abscess.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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