[Intracranial cystic lesions]

Clinical problem: Intracerebral cysts are common findings in imaging of the neurocranium and are not always clinically significant. The pathological spectrum of intracerebral cysts is, however, very broad and in addition to incidental findings includes developmental disorders, malformation tumors, primary and secondary neoplasms and infectious etiologies, such as cerebral abscess formation, cysticercosis or residuals after congenital cytomegalovirus infections. Intracerebral cystic defects may be caused by inflammatory central nervous system (CNS) diseases, such as multiple sclerosis as well as by mitochondriopathies, leukodystrophy, electrolyte disturbances or osmotic demyelination syndrome or brain infarctions, e.g. after lacunar infarctions or as encephalomalacic changes after severe traumatic brain injury.

Radiological standard procedures: In addition to the radiological findings of cysts in magnetic resonance imaging (MRI) or in computed tomography (CT), the localization, patient age, patient medical history and laboratory diagnostics are helpful for the differential diagnostics.

Methodical innovation: In addition to the morphological assessment, advanced MRI techniques, such as diffusion-weighted imaging for epidermoids or the use of MR spectroscopy, can provide valuable information for the differential diagnosis.

Performance/assessment: Intracranial cysts can be subdivided into intraventricular and periventricular cysts, intra-axial cysts and cysts in the external fluid-filled spaces. Associated tumor nodules and the contrast medium behavior of the cyst walls and/or associated soft tissue components as well as the reaction of the adjacent parenchyma are helpful for the diagnosis and assessment.