Neuroimaging of infections

Abstract

Summary:Neuroimaging plays a crucial role in the diagnosis and therapeutic decision making in infectious diseases of the nervous system. The review summarizes imaging findings and recent advances in the diagnosis of pyogenic brain abscess, ventriculitis, viral disease including exotic and emergent viruses, and opportunistic disease. For each condition, the ensuing therapeutic steps are presented. In cases of uncomplicated meningitis, cranial computed tomography (CT) appears to be sufficient for clinical management to exclude acute brain edema, hydrocephalus, and pathology of the base of skull. Magnetic resonance imaging (MRI) is superior in depicting complications like sub-/epidural empyema and vasculitic complications notably on FLAIR (fluid-attenuated inversion recovery)-weighted images. The newer technique of diffusionweighted imaging (DWI) shows early parenchymal complications of meningitis earlier and with more clarity and is of help in differentiation of pyogenic abscess (PA) from ring enhancing lesions of other etiology. Proton magnetic resonance spectroscopy (PMRS) seems to produce specific peak patterns in cases of abscess. The presence of lactate cytosolic amino acids and absence of choline seems to indicate PA. Also in cases of suspected opportunistic infection due to toxoplasma DWI may be of help in the differentiation from lymphoma, showing no restriction of water diffusion. In patients with herpes simplex and more exotic viruses like West Nile and Murray Valley virus DWI allows earlier lesion detection and therapeutic intervention with virustatic drugs.

Comparative Evaluation of Fungal, Tubercular, and Pyogenic Brain Abscesses with Conventional and Diffusion MR Imaging and Proton MR Spectroscopy

“…1 Fungal abscesses appear as solid or ring-enhancing lesions in patients who are immunocompetent. 2 In patients who are immunocompromised, MR imaging shows patchy or punctate T2 hyperintensity with frequently absent enhancement on postcontrast images. 2,3 Conventional MR imaging shows similar features in the pyogenic, tubercular, and fungal abscesses and lacks specificity with respect to the identification of the offending microorganisms.…”

“…2 In patients who are immunocompromised, MR imaging shows patchy or punctate T2 hyperintensity with frequently absent enhancement on postcontrast images. 2,3 Conventional MR imaging shows similar features in the pyogenic, tubercular, and fungal abscesses and lacks specificity with respect to the identification of the offending microorganisms. 1,2,4 In recent years, there has been an effort to characterize the etiologic agents on the basis of diffusion-weighted imaging (DWI), magnetization transfer (MT), and in vivo proton MR spectroscopy (PMRS).…”

“…2,3 Conventional MR imaging shows similar features in the pyogenic, tubercular, and fungal abscesses and lacks specificity with respect to the identification of the offending microorganisms. 1,2,4 In recent years, there has been an effort to characterize the etiologic agents on the basis of diffusion-weighted imaging (DWI), magnetization transfer (MT), and in vivo proton MR spectroscopy (PMRS). [5][6][7][8][9][10] On DWI, low ADC has been found in fungal and tubercular abscesses similar to pyogenic abscesses.…”

In Vivo Proton MR Spectroscopy Evaluation of Pyogenic Brain Abscesses: A Report of 194 Cases

“…Conventional MR imaging also shows similar features in the pyogenic, tubercular, and fungal abscesses and lacks specificity with respect to the identification of the offending microorganisms. [3][4][5] It is important to make a rapid diagnosis of brain abscess to provide appropriate treatment. In vivo 1 H-MR spectroscopy, DWI, and DTI are currently being used routinely to assist in the differential diagnosis of focal and diffuse intracranial pathologies.…”

Ventriculitis: a rare case of primary cerebral toxoplasmosis in AIDS patient and literature review

“…Other forms of CNS involvement are rare. In cases of severe immunosuppression, the neuroimages can be completely atypical, misleading radiologists and clinicians [4]. In this report we described an unusual presentation of cerebral toxoplasmosis in an adult AIDS patient in whom ventriculitis and obstructive hydrocephalus without evidence of focal parenchymal lesion were observed as the primary manifestations of cerebral toxoplasmosis.…”