MRI Findings in an Immunocompromised Boy with CNS Fungal Infection

Abstract

An immunosuppressed 11-year-old with relapsed T-cell leukemia presented with subacute onset fever, headache and a “heavy” right hand. Neurologic examination revealed right-sided hemiparesis and hypesthesia. Magnetic resonance imaging (MRI) 24 hours after symptom onset disclosed lesions involving the right cerebellar hemisphere, left putamen, and cortex in the right frontal lobe and left frontoparietal region (Figure 1). The lesions were gyriform, T1 hypointense, non-enhancing, and T2 hyperintense, with blooming of the larger lesions on the gradient echo sequence consistent with hemorrhage. Interestingly, on fluid attenuation inversion recovery (FLAIR) imaging, the lesions were predominantly isointense with only a small peripheral rim of increased signal. The lesions demonstrated increased signal on the diffusion weighted sequences (DWI) and decreased signal on the apparent diffusion coefficient (ADC) map in keeping with restricted diffusion. There was minimal edema and mass effect. Cerebrospinal fluid (CSF) showed normal glucose, protein, red and white blood cell counts. Flow cytometry did not reveal leukemic cells. There was no serum or CSF evidence of acid-fast bacilli, toxoplasma, enterovirus or herpes simplex virus. Echocardiogram was normal. Biopsy of a lung infiltrate was non-diagnostic. The clinical course fluctuated, with worsening hemiparesis, expressive language difficulties and depressed level of consciousness, which responded only temporarily to corticosteroids. The lesions progressed in size despite maximal empiric broad-spectrum antimicrobial treatment against bacteria, viruses, fungi and toxoplasma. Repeat MRI one week after onset showed enlargement of the lesions. They were hyperintense on T1 sequences and without clear contrast-enhancement. They continued to show restricted diffusion. MRI 17 days after symptom onset again showed lesion growth. There was ring enhancement and significant vasogenic edema with mass effect (Figure 2). The lesions no longer showed restricted diffusion. Due to disease progression despite maximal therapy, the brain lesions were not biopsied and the child was transferred to the palliative care service. He died at home six weeks after symptom onset. Postmortem brain examination showed multifocal chronic fungal abscesses in the frontal lobes, left putamen and right cerebellum. Central coagulative necrosis harboured thrombosed blood vessels bearing fungal angioinvasion. Though morphologically suggestive of Aspergillus, the hyphae were degenerate, precluding definitive identification (Figure 3). Abscess capsules were well-formed and contained multinucleated giant cells and focal granulomata (Figure 4). Adjacent parenchyma was gliotic and focally degenerate, suggesting chronic edema. Leukemic infiltrates were not present. We report a case of multifocal fungal cerebritis with MRI showing restricted diffusion. At the time of presentation, the