Pediatr Radiol (2006) 36: 1190–1193 DOI 10.1007/s00247-006-0275-2

CASE REPORT

Hanefi Yildirim . Nimet Kabakus . Mustafa Koc . Ayse Murat . Feyza İnceköy Girgin

Meningoencephalitis due to anthrax: CT and MR findings

Received: 31 March 2006 / Revised: 6 June 2006 / Accepted: 11 June 2006 / Published online: 12 August 2006 # Springer-Verlag 2006

Abstract Anthrax is primarily a disease of herbivores, but it also causes cutaneous, respiratory and gastrointestinal infections in humans. Bacillus anthracis is an uncommon cause of meningitis and generally produces a haemorrhagic meningoencephalitis. We present the CT and MR findings of anthrax meningoencephalitis due to the cutaneous form of anthrax in a 12-year-old boy. They showed focal intracerebral haemorrhage with leptomeningeal enhancement. Keywords Anthrax . Encephalitis . CT . MRI

Introduction Anthrax is primarily a disease of herbivores, but it also causes cutaneous, respiratory and gastrointestinal infections in humans [1]. Meningoencephalitis as a complication of this disease is even rarer and is usually associated with lack of immunity and poor industrial hygiene [2]. It develops as a result of lymphohaematogenous spread from the primary lesions [3]. Brain CT [2, 4] and MR findings [4] have been previously reported. We present the CT and MR imaging findings of anthrax meningoencephalitis in a child demonstrating focal intracerebral haemorrhage with leptomeningeal enhancement.

H. Yildirim (*) . M. Koc . A. Murat Department of Radiology, Firat University, Elazig, 23119, Turkey e-mail: [email protected] Tel.: +90-424-2333555 Fax: +90-424-2376773 N. Kabakus . F. İnceköy Girgin Department of Paediatric Neurology, Firat University, Elazig, Turkey

Case report A 12-year-old boy was admitted with sudden loss of consciousness and seizures. His pupils were equal and reactive to light. Axillary body temperature was 37°C. Respiration was irregular and pulse rate was 90/min. White blood cell count was 18,700/mm3. Erythrocyte sedimentation rate was 3 mm/h. Blood biochemistry was normal except for AST (328 U/l) and ALT (93 U/l). C-reactive protein was elevated at 86 mg/dl. Further history revealed that the patient had slaughtered a sick sheep 1 week before admission. Physical examination revealed four perioral vesicles (0.5×0.5 cm) surrounded by erythema suggesting that the infection had been initiated through a break in the skin (cutaneous anthrax). Lumbar puncture demonstrated CSF under pressure and haemorrhagic with a white cell count of 1,465/mm3, of which 100% were polymorphonuclear leucocytes. Large gram-positive bacilli were seen in the CSF smear. Bacillus anthracis was isolated from cultures of CSF and blood. Unenhanced brain CT (Fig. 1) revealed a 1×1-cm hyperdense haemorrhage in the left posterior frontoparietal region. Contrast-enhanced CT (Fig. 1) revealed diffuse leptomeningeal enhancement. MR imaging of the brain was performed with spin-echo T1-weighted (T1-W), T2-weighted (T2-W), fluid-attenuated inversion recovery (FLAIR), and contrast-enhanced T1-W images on a 1.5-T system. This showed multiple areas of abnormal signal, especially in the left posterior parietal region and the basal ganglia bilaterally (Fig. 2) that were isointense on T1-W images and hyperintense on T2W and FLAIR images. Contrast-enhanced T1-W images showed diffuse leptomeningeal enhancement of the cerebrum and cerebellum and enhancement of the basal ganglia (Fig. 3). Haemorrhage in the left posterior frontoparietal region was hyperintense on FLAİR images. The radiological findings were consistent with haemorrhagic meningoencephalitis due to the anthrax. Although treatment of anthrax meningitis was started immediately, the patient died 1 day after admission. Autopsy was not performed.

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Fig. 1 CT. a Unenhanced axial CT shows left frontoparietal haemorrhage. b Contrast-enhanced axial CT scan shows diffuse leptomeningeal enhancement

Discussion Bacillus anthracis is a large, gram-positive, aerobic sporeforming bacillus. The principal virulence factors of B. anthracis are encoded on two plasmids, one involved in the synthesis of a polyglutamyl capsule that inhibits phagocytosis of vegetative forms and the other bearing the genes for the synthesis of the exotoxins it secretes [5]. Infection is initiated with the introduction of the spore through a break

Fig. 2 Axial FLAIR MRI. a Increased intensity in left posterior parietal cortex. b Increased intensity in the basal ganglia bilaterally

in the skin (cutaneous anthrax) or through the mucosa (gastrointestinal anthrax). Meningoencephalitis can develop from any primary focus, but survival appears to be most likely if meningoencephalitis develops from cutaneous anthrax [6].

1192 Fig. 3 MRI. a Contrast-enhanced axial T1-W image shows diffuse leptomeningeal and basal ganglia enhancement. b Contrast-enhanced axial T1-W image shows diffuse leptomeningeal enhancement. c Contrast-enhanced sagittal T1-W image shows diffuse leptomeningeal and basal ganglia enhancement

Haemorrhagic meningitis should raise suspicion of anthrax infection, particularly if gram-positive rods are demonstrated on Gram stain. The diagnosis of anthrax meningitis is supported by the presence of haemorrhagic CSF with a polymorphonuclear pleocytosis and grampositive rods on peripheral neutrophilic pleocytosis, with prominent band forms seen in inhalation cases. This pleocytosis is less marked in those with cutaneous anthrax [7]. Initial symptoms often include sudden onset of malaise, intense headache, fever, chills, nausea and vomiting, sometimes in the absence of meningism [8]. CT findings of anthrax meningoencephalitis include lesions at the cerebral grey–white matter junction and diffuse meningeal enhancement [2, 4]. Contrast-enhanced CT and MRI reveal diffuse meningeal enhancement. The differential diagnosis of anthrax meningoencephalitis includes subarachnoid or intracerebral haemorrhage, bacterial or aseptic meningitis, and encephalitis. MR imaging with contrast medium can easily distinguish haemorrhagic meningoencephalitis from subarachnoid or intracerebral

haemorrhage [4]. Haemorrhagic encephalitis can be seen in herpes simplex virus type I encephalitis [9] and rubella and varicella/zoster infections in immunocompromised patients [10, 11]. To differentiate other haemorrhagic or nonhaemorrhagic meningoencephalitides, Gram staining and culture of CSF should be performed [12]. Anthrax meningoencephalitis has a high mortality, even with aggressive antibiotic treatment and supportive therapy. Mortality approaches 100%. Early and aggressive antimicrobial therapy is critical. Occasionally, patients treated with antibiotics have survived [13]. Penicillin is used for the treatment of all forms of anthrax, although isolates may rarely be penicillin-resistant [14]. Fluoroquinolones were often effective in patients with inhalation and cutaneous anthrax during an outbreak in autumn 2001 [15]. Anthrax meningitis is almost always fatal, with death occurring 1–6 days after the onset of illness, despite intensive antibiotic therapy. This is exemplified by our patient who did not respond to treatment and died within 1 day.

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In conclusion, anthrax meningitis is an extremely rare entity that should always be distinguished from subarachnoid haemorrhage due to cerebrovascular accident and from other forms of haemorrhagic meningitis due to other agents such as herpes viruses or fungi. The clinician should consider anthrax meningitis if there is a history of contact with infected animals or their products. CT and MR scans may help the differential diagnosis. Diffuse leptomeningeal enhancement is prominent [4].

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