The MRI diagnotstics of cerebral edema. The discrimination of cytotoxic and vasogenic edema

Brain edema, defined as localized or extensive swelling of brain tissue, arises from various pathologies, including trauma, ischemia, hypoxic damage, inflammation (e.g., infection), rapidly growing tumors, and obstructive hydrocephalus. The main types are cytotoxic, vasogenic, and interstitial edema. Cytotoxic edema, typically affecting gray matter, occurs in acute infarction, hypoxic injury, and later stages of cranial trauma. Vasogenic edema, primarily affecting white matter, is associated with tumor growth, infection, early stages of trauma, and any condition disrupting the blood-brain barrier. Posterior reversible encephalopathy syndrome (PRES) is a specific pathology associated with vasogenic edema. Less common are osmotic or hydrostatic edema and brain swelling associated with hydrocephalus. Radiologically, CT scans demonstrate localized or generalized areas of hypodensity with CSF space constriction. Conventional MRI sequences show increased water signal in edematous areas (hyperintensity on FLAIR and T2-weighted images, hypointensity on T1-weighted images) and may reveal underlying causes such as tumors, abscesses, or hemorrhage. Diffusion-weighted imaging differentiates edema types: vasogenic and hydrostatic edema exhibit high ADC values (increased diffusion), while cytotoxic edema shows low ADC values (restricted diffusion). Although CT and conventional MRI cannot directly distinguish between edema types, identifying the underlying pathology can indirectly indicate the type of edema. Diffusion-weighted imaging, by detecting diffusion changes, allows for direct differentiation of edema types. CT scans and conventional MRI baseline sequences are unable to differentiate between edema caused by various factors. However, identifying the underlying cause can help classify the type and cause of brain edema indirectly. Diffusion-weighted imaging techniques enable the differentiation of edema by detecting diffusion restriction or by revealing high signal intensity on ADC maps.