Medical Imaging of CNS Infection

Abstract

For mild meningitis, CT and MRI often have no finding or only show mild hydrocephalus. For bacterial meningitis, CT and MRI may show leptomeningeal enhancement and mild hydrocephalus. Some cases have exudate in the basal cistern, and some cases are associated with arterial or venous infarctions. Some cases are also associated with brain abscess or subdural empyema. CT and MRI can clearly show these complications. Brain abscesses reveal ring enhancement with severe peripheral white matter edema in CT and MRI. DWI and MRS are helpful for differential diagnosis of brain abscess with tumor necrosis. MRI is better than CT to detect encephalitis, showing hyperintensity on T2WI and FLAIR. In some instances, the affected brain tissue has diffusion restriction, indicating hyperintensity on DWI, and some have contrast enhancement because of BBB disruption. Central nervous system (CNS) infections include meningitis (Figs. 7.1-7.10), brain abscess (Figs. 7.7, 7.11-7.17), epidural and subdural empyema (Fig. 7.7), encephalitis (Figs. 7.18-7.25), and meningoencephalitis (Figs. 7.6, 7.9, and 7.25). Besides, CNS infections may involve the spinal cord and spinal canal, namely encephalomyelitis and meningoencephalomyelitis. CNS infection pathogenesis includes the virus, bacteria, fungus (Figs. 7.3 and 7.6), and parasites (Fig. 7.17). Some cases of CNS infections involve post-infectious encephalitis, such as acute disseminated encephalomyelitis (ADEM) (Figs. 7.26 and 7.27). However, the pathogen of numerous CNS infection cases has yet to be revealed (Fig. 7.5).