Aspergillus is a common fungus in the environment. Humans are usually infected by inhalation of spores, the most common cause in immunocompetent patients and can lead to local infections in the lungs, sinuses, or other sites. In immunocompromised subjects, it can lead to life-threatening, invasive infections; this is very rare in immunocompetent patients. Today we share a rare case of aspergillosis in immunocompetent patients and their imaging manifestations.
Case profile
A formerly able-bodied 6-year-old girl was taken to the emergency room after experiencing an isolated convulsive crisis. Patients were diagnosed with febrile seizures and viral infections, for which supportive measures were taken. A week later, the patient developed progressive right-sided hemiplegia and underwent a non-enhanced CT scan (Figure 1), which was reported as a right frontal lobe tumor; subsequently, the patient was transferred to the hospital for further examination and a brain MRI was performed.
Figure 1 Non-enhanced CT of the basal axis of the brain shows extensive angioedema of the right frontal lobe with scattered in the bleeding area with minimal mass effect. Source: Department of Radiology, High Specialty Regional Hospital of elBajio, Mexico, 2019
Imaging manifestations:
MrI (Figure 2) shows an irregularly shaped right frontal lobe lesion with blurred edges, peripheral angioedema, and some bleeding areas; despite the size of the lesion and extensive angioedema, the lump effect is mild. In the augmentation scan, there is an "open ring" of enhancement. No proliferation restrictions were found. Other smaller lesions with similar features are found. Head and neck imaging shows no signs of the course of infection. Biopsy shows granulomatous inflammatory processes with vasodilation. Patients begin steroid use and supportive therapy.
Fig. 2a Brain basal axis T1 weighted image shows an irregular, uneven lesion of the right frontal lobe, the edges are not clear, and the high-intensity frontal lobe lesion suggests bleeding
Figure 2b Brain basal axial FLAIR weighted image shows extensive right frontal angioedema with minimal mass effect
Figure 2c Basal axis sensitivity enhancement image of the brain shows multiple right frontal lobe lesions, representing microbleeds
Figure 2d Axial dispersion weighted image of the base of the skull shows the large high signal clear area of the right frontal lobe
Figure 2e Brain basal axis ADC plot shows a wide range of high signals consistent with DWI with clear boundaries
Figure 2f Axial gadolinium-enhanced t1 weighted image of the skull base shows an irregular "open loop" enhancement in the right frontal lobe region. Other similar smaller satellite lesions are present at the department of Radiology, High Specialty Regional Hospital of elBajio, Mexico, 2019
No improvement was achieved under the established treatment, so a second MRI examination (Figure 3) was performed, showing an increase in the number and size of lesions.
Figure 3a Axel FLAIR shows extensive angioedema of the right frontal lobe with increased mass effect
Figure 3b Followed up with gadolinium-enhanced T1 weighted images showing surgical changes due to biopsy and an increase in the size of satellite lesions
Figure 3c follow-up axial gadolinium-enhanced T1 weighted image shows a new large right parietal lobe lesion showing open annular intensification. Source: Department of Radiology, High Specialty Regional Hospital of elBajio, Mexico, 2019
Case discussion
Aspergillus is a common fungus in the environment. Humans are usually infected by inhalation of spores, the most common cause in immunocompetent patients and can lead to local infections in the lungs, sinuses, or other sites. In immunocompromised subjects, it can lead to life-threatening, invasive infections; this is very rare in immunocompetent patients. Aspergillosis of the central nervous system is becoming more common due to the increased prevalence of immunosuppression, as well as the increase in life expectancy in these patients.
When Aspergillus infects the central nervous system, it usually reaches the central nervous system through blood transmission; direct inoculation may come from the paranasal sinuses or trauma (including surgery). The prognosis for aspergillosis is poor, especially since its diagnosis usually occurs later in the course of the disease. The reported mortality rate was 88 per cent. Diagnostics may be delayed. Because symptoms are nonspecific, especially in immunocompetent patients, this CNS infection is rarely suspected.
Clinical manifestations of aspergillosis are nonspecific; they may include altered mental status, behavioral alterations, hemiplegia, dysarthria, drowsiness, and seizures. Although the disease is contagious, it may or may not be feverish. These signs and symptoms in immunosuppressed patients require neuroradiological evaluation. Immunocompetent patients may have fewer specific signs and symptoms; in addition, invasive fungal infections are not considered part of the differentiation of these patients.
Imaging plays an important role in the management of these cases, but the features found are not always conclusive. Aspergillosis is characterized by hemorrhagic infarction (due to aspergillosis invading blood vessels) and abscesses; however, encephalitis, meningitis, and fungal aneurysms may also occur. The most common imaging manifestations are thick-walled fortified (host defense) lobular abscesses, severe inflammation involving adjacent structures (paranasal sinuses, dura with focal meningitis, osteomyelitis), and extensive parenchymal edema; more than half of patients have callosomal lesions (affected only in a few diseases), a sign that helps narrow the differential diagnosis. In cases of Aspergillus abscesses, DWI/ADC target lesions are common. This can be explained by central necrosis and the external hyphal margins with peripheral inflammation.
conclusion
Aspergillosis is a rare but often fatal complication of invasive aspergillosis. Unclear signs and symptoms complicate treatments in these patients, and a lack of suspicion can delay diagnosis and treatment.
Common differential diagnoses: advanced glioma, acute disseminated encephalomyelitis, bacterial abscess.
Imaging plays an important role in the diagnosis of disease; therefore, radiologists should use it as a differentiator between immunocompetent and immunocompromised patients in order to begin appropriate antifungal therapy as early as possible.
Cerebrospinal fluid examination is determined to be aspergillus encephalitis, positive for ASPERGI PCR. Antifungal therapy was initiated, with a positive clinical and radiological response.
Compiled from: https://www.eurorad.org/case/17700