Neuroimaging of Central Nervous System Infections in childhood
MedantaThe Medicity India
Central nervous system (CNS) infections commonly present with non-specific features. Neuroimaging plays an important role in the integrated clinical-radiological diagnosis and management of CNS infections.Magnetic-resonance-imaging (MRI) is more sensitive than CT for diagnosis of various CNS infections. Standard sequences recommended for CNS infections include T1-sagittal and axial, T2-axial and coronal, fluid-attenuated-inversion-recovery, post-contrast T1, and diffusion-weighted. Proton MR-spectroscopy studies the patterns of brain metabolites non-invasively and helps determine the etiology of brain abscesses or intracranial-space-occupying lesions. Diffusion-weighted and diffusion-tensor-imaging aid differentiation of abscesses from tumours, cerebritis from infarcts, lymphoma from toxoplasmosis etc. Magnetic-transfer-imaging is especially useful in tuberculous meningitis for demonstration of meningeal enhancement even on pre-contrast T1 images.Infections such as neurocysticercosis show characteristic imaging appearances according to their pathological stages in the brain. Gradient-echo based sequences such as CISS help in detection of neurocysticerci in CSF spaces.
Although all cases of acute bacterial meningitis do not require neuroimaging, suspicion of complications such as ventriculitis, brain abscess, hydrocephalus, empyema and vasculopathy/thrombosis need radiological corroboration.
MRI should ideally be done in all cases for evaluation of encephalitis;Characteristic patterns of involvement may help in predicting the etiological agent such as temporal lobe and hippocampus in herpes; diffuse white-matter in HIV, JC virus and SSPE; anterior temporal lobes and white-matter in congenital CMV; splenium of corpus callosum in influenza and adenovirus; thalamus andsusbstantianigrain Japanese and West-Nile encephalitis; basal ganglia in EBV, HIV and Mycoplasma; dorsal brainstem in enterovirus and rabies, spinal cordgray matter in enterovirus and varicella, and spinal cord white matter in HIV. MRI also excludes closely mimicking clinical conditions such as ADEM.
The clinician can judiciously use neuroimaging in CNS infections to corroborate the clinical diagnosis and exclude other differentialsin the appropriate clinical context
Disclaimer: The Views and opinions expressed in the articles are of the authors and not of the journal.
Mid City Hospital, 3-A Shadman II
Jail Road, Lahore ,Pakistan