KEY FACTS Terminology Brain parenchyma infection caused by herpes simplex virus type 1 (HSV1) Typically reactivation in immunocompetent patients Imaging Best imaging clue: T2/FLAIR hyperintensity of limbic system (medial temporal and inferior frontal cortex) with DWI restriction Typically bilateral disease,…
KEY FACTS Terminology Collection of pus in subdural or epidural space, or both (15%); subdural much more common Subdural empyema (SDE), epidural empyema (EDE) Imaging Best diagnostic clue: Extraaxial collection with enhancing rim, DWI positive Supratentorial typical EDE: Often adjacent…
KEY FACTS Terminology Ventricular ependyma infection related to meningitis, ruptured brain abscess, or ventricular catheter Imaging Best imaging clue: Ventriculomegaly with debris level, abnormal ependyma, periventricular T2/FLAIR hyperintensity DWI Restriction of layering debris with low ADC is characteristic T1WI C+…
KEY FACTS Terminology Focal pyogenic infection of brain parenchyma, typically bacterial; fungal or parasitic less common 4 pathologic stages: Early cerebritis, late cerebritis, early capsule, late capsule Imaging Ring-enhancing lesion with T2 hypointense rim and central diffusion restriction characteristic Imaging…
KEY FACTS Terminology Acute or chronic inflammatory infiltration of pia, arachnoid, and cerebrospinal fluid (CSF) Classified as acute pyogenic (bacterial), lymphocytic (viral), chronic (tuberculosis or granulomatous) Imaging Imaging best delineates complications: Empyema, ischemia, hydrocephalus, cerebritis/abscess, ventriculitis FLAIR MR: Hyperintense signal…
Overview of CNS Infections General Considerations Classification : Infectious diseases can be classified into congenital/neonatal and acquired infections. They can be further subdivided by etiology, i.e., bacterial, viral, fungal, parasitic, and rickettsial diseases. Infectious diseases can have different manifestations depending…
KEY FACTS Terminology Cerebrospinal fluid (CSF)-filled parenchymal cavity Deep, unilateral/bilateral cavity/excavation Usually communicates with ventricle &/or subarachnoid space Lined by reactive gliosis/astrocytic proliferation Congenital (perinatal brain destruction) or acquired (trauma, infection, etc) Imaging Best diagnostic clue: CSF-filled cavities with enlarged…
KEY FACTS Terminology Choroid plexus cysts (CPCs) Nonneoplastic, noninflammatory cysts Contained within choroid plexus; lined by compressed connective tissue Imaging General Typically in atria of lateral ventricle Usually small (2-8 mm) Rare: Large cysts (> 2 cm) Usually multiple, often…
KEY FACTS Terminology Nonneoplastic intrapineal glial-lined cyst Imaging CT Sharply demarcated, smooth cyst behind 3rd ventricle 80% < 10 mm (can be large; reported up to 4.5 cm) Fluid iso-/slightly hyperdense to cerebrospinal fluid (CSF) 25% Ca++ in cyst wall…
KEY FACTS Terminology Perivascular spaces (PVSs) Also known as Virchow-Robin spaces Pial-lined interstitial fluid-filled structures Accompany penetrating arteries Do not communicate with subarachnoid space Imaging Clusters of variably sized, well-delineated nonenhancing cysts PVSs occur in all locations, at all ages;…