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Intracranial Cysts,-Radiologic-Pathologic Correlation and Imaging Approach Radiology: Volume 239: Number 3-June 2006 Anne G. Osborn, MD Michael Preece, MD,Classification,This stable not include cystic and necrotic neoplasms, as well as brain abscesses,Choroid Plexus Cysts (CPCs),Pathologic Findings Nonneoplastic epithelial-lined cysts of the choroid plexus Most common of all intracranial neuroepithelial cysts, occurring in up to 50% of autopsy cases Most are bilateral and located in the lateral ventricular atria Most CPCs are asymptomatic , typically in neonates and older adults Symptomatic lesions are rare since the atria typically enlarge to accommodate the cyst,Transverse graphicrepresentation shows multiple cystic masses in the choroid plexus glomi (arrows). Most CPCs are actually degenerative xanthogranulomas,Pathologic Findings Occur when lipid accumulates in the choroid plexus from degenerating and/or desquamating choroid epithelium Can be almost entirely cystic, nodular, or partially cystic. Appear as nodular, yellowish gray masses within the glomus of the choroid plexus. Most are small, measuring 28 mm in diameter. Cysts greater than 2 cm are rare.,Choroid Plexus Cysts (CPCs),Choroid Plexus Cysts (CPCs),Microscopic Microcysts containing nests of foamy lipid-laden histiocytes Chronic inflammatory lymphocytic and plasma cell infiltrates, cholesterol clefts, hemosiderin, and peripheral psammomatous calcium,Choroid Plexus Cysts (CPCs),CT Iso- to slightly hyperattenuated on nonenhanced CT scans compared with CSF Peripheral calcification is common Enhancement varies from none to striking,Choroid Plexus Cysts (CPCs),MRI Iso- or hyperintense on precontrast T1-weighted MR images compared with CSF and show rim or nodular contrast enhancement Usually hyperintense to CSF on T2WI The majority do not become completely hypointense (suppress) on FLAIR images and remain slightly or moderately hyperintense to CSF Two-thirds show restriction (high signal intensity) on DWI,Transverse contrast-enhanced T1-weighted MR image in a healthy 52-year-old man shows bilateral CPCs with peripheral and nodular enhancement (arrows).,Choroid Plexus Cysts (CPCs),Differential Diagnosis Ependymal cyst: no enhancement Villous hyperplasia of the choroid plexus: rare , enhances strongly , Colloid cysts: typically occur only at the foramen of Monro,Enlarged PVSs (Virchow-Robin spaces),Pathologic Findings Pial-lined interstitial fluid-filled structures that accompany penetrating arteries and veins, do not communicate directly with the subarachnoid space Location: inferior basal ganglia, midbrain, deep white matter, and subinsular cortex. They can also be found in the region of the thalami, dentate nuclei, corpus callosum, and cingulate gyrus,Enlarged PVSs,Pathologic Findings Microscopically, PVSs consist of a single or double layer of invaginated pia. They are typically very small or inapparent as they pass through the cortex, enlarging in the subcortical white matter. They are typically not associated with gliosis in the surrounding parenchyma,Coronal gross slice of autopsied brain with postmortem gas in bilateral enlarged PVSs,Enlarged Pvss,Imaging Smoothly demarcated fluid-filled cysts Less than 5 mm in diameter Isointense to CSF at all sequences 25% may have a small rim of slightly increased signal intensity No enhncement, focal mass effect tat cribl,（筛板样小空腔） or cribriform state,Transverse contrast-enhanced T1-WI shows typical nonenhancing enlarged PVSs in right basal ganglia. The cluster of variably sized cysts is a common appearance,Transverse T2-weighted MR image shows multiple bizarre-appearing cysts (arrows) in centrum semiovale and subcortical white matter of both hemispheres. The cysts vary in size and focally expand but otherwise spare the overlying cortex,Enlarged Pvss,Differential Diagnosis Multiple lacunar infarcts: many exhibit adjacent parenchymal hyperintensity Cystic neoplasms : rarely exhibit signal intensity exactly like the CSF Infectious cysts: Neurocysticercosis cysts may have a scolex (parasite head), cyst walls often enhance. cysts may be multiple but do not typically occur in clusters within the brain parenchyma,Ependymal Cysts,Pathologic Findings Rare, benign, ependymal-lined cysts of the lateral ventricle or juxtaventricular region of the temporoparietal region and frontal lobe Infrequently identified in the subarachnoid spaces, brainstem, and cerebellum Most are incidental, but symptomatic cysts may manifest with headache, seizure, and/or obstructive hydrocephalus,Ependymal Cysts,Pathologic Findings Are thought to arise from sequestration of developing neuroectoderm during embryogenesis They are thin walled and filled with clear serous fluid secreted from ependymal cells Columnar cells, with or without cilia（纤毛）, line ependymal cysts. They have vesicular nuclei and eosinophilic cytoplasm,Ependymal Cysts,Imaging The best diagnostic clue is a nonenhancing thin-walled CSF-containing cyst of the lateral ventricle,Transverse FLAIR MR image shows ependymal cyst within enlarged atrium of the left lateral ventricle (open arrow). Signal intensity was isointense to CSF at all pulse sequences. Note lateral displacement of choroid plexus (solid arrow).,Ependymal Cysts,Differential Diagnosis CPC: are usually not identical to CSF at all imaging sequences, bilateral, and often enhance Arachnoid cyst: occur in the subarachnoid spaces Neurocysticercosis: hyperintense rim and scolex on FLAIR images Asymmetric ventricles: without displacement of choroid plexus,Neuroglial Cysts,Pathologic Findings Benign epithelial-lined lesions that occur anywhere in the neuraxis , representing fewer than 1% of intracranial cysts The frontal lobe is the most typical location , intraparenchymal neuroglial cysts are more common than extraparenchymal cysts,Neuroglial Cysts,Pathologic Findings Intraparenchymal neuroglial cysts are congenital lesions, arising from embryonic neural tube elements that become sequestered within the developing white matter They are rounded, smooth, and unilocular and contain clear fluid that resembles CSF. They are lined by ependymal (columnar epithelium) or choroid plexus cells (low cuboidal epithelium),Neuroglial Cysts,Imaging The best diagnostic clue is a nonenhancing CSF-like parenchymal cyst with minimal to no surrounding signal intensity abnormality The cysts are benign-appearing lesions with smooth, rounded borders Size is variable,Transverse FLAIR MR image shows typical neuroglial cyst (straight arrow) adjacent to left temporal horn. The cyst appears well demarcated without surrounding gliosis and has the same appearance as CSF at all sequences. This cyst does not communicate with the ventricle (curved arrow),Transverse FLAIR MR image demonstrates neuroglial cyst in the choroid fissure (arrow),Neuroglial Cysts,Differential Diagnosis Enlarged PVS: multiple and cluster around the basal ganglia Infectious cyst: typically smaller than 1 cm and can partially enhance Porencephalic cyst: communicate with the lateral ventricle and show surrounding gliosis Arachnoid cyst: typically extraaxial,Pineal Cysts,Pathologic Findings Often with some residual pineal parenchyma Common: up to 10% of cases at routine imaging and in 20%40% of cases at autopsy Three distinct layers: fibrous connective tissue pineal parenchyma with or without calcium finely fibrillar glial tissue that often contains hemosiderin deposits,Pineal Cysts,Pathologic Findings Origin : Ischemic glial degeneration, enlarged preexisting cysts,and enlargement of the embryonic pineal cavity Unilocular cysts with a soft tan to yellow wall. Contents vary from clear to yellow (most common) to hemorrhagic. 80% are smaller than 1 cm in diameter,Sagittal gross postmortem slice demonstrates cystic pineal gland (arrow) with thin cyst wall,Pineal Cysts,Imaging Unilocular fluid-filled mass within the pineal gland Attenuation or signal intensity varies with cyst content One-fourth have rim or nodular calcium in the cyst wall Rim or nodular enhancement is also common 55%60% are slightly hyperintense to CSF On T1-WI. Most do not appear hypointense on FLAIR images 60% enhance with use of contrast material,Sagittal contrast-enhanced T1-weighted MR image shows classic benign pineal cyst (straight arrows) with rim enhancement and mild mass effect (note slight compression, displacement of tectal plate curved arrow),Pineal Cysts,Differential Diagnosis Pineocytoma: more likely to have solid components, but it may be impossible to distinguish the two with imaging studies alone Other cysts in the quadrigeminal cistern that mimic pineal cysts include arachnoid cysts (no calcium) and, rarely, epidermoid cysts,Arachnoid Cysts,Pathologic Findings Benign, congenital, intraarachnoidal space-occupying lesions that are filled with clear CSF Do not communicate with the ventricular system Tend to be unilocular, smoothly marginated expansile lesions that are molded by the surrounding structures Are common, representing 1% of all intracranial masses. The incidence is somewhat higher in men,Submentovertex view of autopsied brain with large middle fossa arachnoid cyst, which is contained within split layers of arachnoid,Arachnoid Cysts,Imaging Sharply demarcated extraaxial cyst that can displace or deform adjacent brain Scalloping of the adjacent calvarium often seen No identifiable internal architecture and does not enhance,Arachnoid Cysts,Imaging Same signal intensity as CSF at all sequences Occasionally, hemorrhage, high protein content, or lack of flow within the cyst may complicate the MR appearance Increased prevalence of coexisting subdural hematomas, especially when they occur in the middle cranial fossa,Transverse T2-weighted MR image shows extraaxial CSF-like arachnoid cyst in anterior middle cranial fossa (straight arrow). The temporal lobe is hypoplastic with posteriorly displaced temporal horn (curved arrow). Transverse diffusion-weighted MR image shows no restriction (an epidermoid cyst would not suppress completely on FLAIR image and would restrict on diffusion-weighted image) and a classic arachnoid cyst (arrows),Arachnoid Cysts,Differential Diagnosis Epidermoid cysts: Arachnoid cysts typically suppress completely on FLAIR images and do not restrict on DWI. Arachnoid cysts displace adjacent arteries and cranial nerves rather than engulf them, as epidermoid cysts often do,Arachnoid Cysts,Differential Diagnosis Chronic subdural hematoma: show CSF signal intensity on MR images and often have an enhancing membrane Porencephalic cyst : often follow a history of trauma or stroke. The cysts are normally surrounded by gliotic brain,Colloid Cysts,Pathologic Findings Benign mucin-containing cysts More than 99% are found wedged in the foramen of Monro. typically attached to the anterosuperior portion of the third ventricular roof. The pillars of the fornix straddle the cyst,Colloid Cysts,Pathologic Findings Other sites, including the lateral ventricles, cerebellar parenchyma, and various extraaxial locations Even relatively small colloid cysts may produce sudden acute hydrocephalus. Occasionally brain herniation with rapid clinical deterioration and even death ensue,Colloid Cysts,Pathologic Findings Derived from embryonic endoderm Smooth and spherical, varying in size Filled with viscous gelatinous material Simple to pseudostratified epithelial lining The epithelial layer rests on a delicate layer of collagen and fibroblasts,Coronal gross specimen shows colloid cyst at the foramen of Monro. Note displacement of septum pellucidum and fornices (white arrow) around the cyst (black arrow). Moderate hydrocephalus is present,Colloid Cysts,Imaging The location is at the foramen of Monro. Well-delineated hyperattenuated mass on nonenhanced CT scans The majority are hyperintense on T1WI and isointense to brain on T2WI. Some demonstrate peripheral rim enhancement . Rapidly expand cysts are often hypointense on T1- and hyperintense on T2-weighted images,Transverse nonenhanced CT scan shows classic hyper attenuated colloid cyst at foramen of Monro (arrow),Colloid Cysts,Differential Diagnosis The most common “lesion“ mistaken for a colloid cyst is CSF flow artifact (MR pseudocyst) caused by pulsatile turbulent CSF flow around the foramen of Monro Occasionally, a neuro cysticus cyst may occur at the foramen of Monro Neoplasms such as subependymoma or choroid plexus papilloma that may occur at the foramen of Monro are much less common and typically enhance,Epidermoid Cysts,Pathologic Findings Congenital inclusion cysts The most common location is the cerebellopontine angle cistern , other place include the fourth ventricle, sellar and/or parasellar regions , cerebral hemispheres or brainstem, even extradural,Epidermoid Cysts,Pathologic Findings All are located off the midline Most are asymptomatic but may result in mass effect, cranial neuropathy, or seizure Occasionally, epidermoid cysts rupture and may excite a granulomatous meningitis,Epidermoid Cysts,Pathologic Findings Arise from ectodermal inclusion during neural tube closure in the 3rd5th week of embryogenesis. Acquired epidermoid cysts may be the result of trauma. The irregular lobulated surface , cyst may grow to encase vessels and nerves.,Epidermoid Cysts,Pathologic Findings The microscopic cyst lining consists of stratified squamous epithelium. Cystic contents usually include debris, keratin, water, and cholesterol Epidermoid cysts do not contain dermal appendages,Sagittal graphic representation shows posterior fossa epidermoid cyst (arrow) wrapping around basilar artery and displacing the brainstem posteriorly,Epidermoid Cysts,Imaging CSF-like mass that insinuates within cisterns, encasing adjacent nerves and vessels On CT scans, most epidermoid cysts are well-defined hypoattenuated masses that resemble CSF and do not enhance,Epidermoid Cysts,Imaging Calcification is present in 10%25% of cases Most epidermoid cysts are isointense or slightly hyperintense to CSF on both T1- and T2WI, restrict on DWI Most do not enhance, although some minimal rim enhancement occurs in approximately 25% of cases,Epidermoid Cysts,Imaging “white epidermoids”: appear hyperattenuated on CT scans because of high protein content. reversed signal intensity on MR images, with high signal intensity on T1- and low signal intensity on T2WI,Transverse nonenhanced CT scan shows slightly lobulated low-attenuation mass in posterior fossa (arrows). Transverse diffusion-weighted image shows markedly restricted diffusion (arrows). Epidermoid cyst was confirmed at surgery.,Epidermoid Cysts,Differential Diagnosis Arachnoid cyst: isointense to CSF at all sequences, displace rather than invade structures such as the epidermoid. Finally, do not restrict on DWI Other disease: Dermoid cysts are typically located along the midline and resemble fat, not CSF. Cystic neoplasms often enhance and do not resemble CSF . Neurocysticercosis cysts often enhance and demonstrate surrounding edema or gliosis,Dermoid Cysts,Pathologic Findings Like epidermoid cysts, dermoid cysts arise from the inclusion of ectodermally committed cells at the time of neural tube closure (3rd5th week of embryogenesis) They tend to occur in the midline sellar, parasellar, or frontonasal regions . Others are midline in the posterior fossa, the fourth ventricle,Dermoid Cysts,Pathologic Findings These cysts increase in size by means of glandular secretion and epithelial desquamation. Growth can lead to rupture of the cyst contents, causing a chemical meningitis that may lead to vasospasm, infarction, and even death Malignant transformation into squamous cell carcinoma has also been described,Dermoid Cysts,Pathologic Findings The capsule of dermoid cysts consists of simple epithelium supported by collagen. In thicker parts, the lining is supplemented with dermis containing hair follicles, sebaceous glands, and apocrine glands The active production of hair and oils by the dermal appendages has been implicated in the earlier rupture when compared with keratin-producing epidermoid cysts,Dermoid Cysts,Pathologic Findings The cyst is a well-defined, lobulated, “pearly“ mass of variable size. The capsule is thicker than that of the epidermoid cyst and often contains plaques of calcification. Characteristically, the cyst contains thick, foul-smelling, yellow material The cysts may also contain hair and/or teeth,Dermoid Cysts,Imaging Unruptured cysts have the same imaging characteristics as fat because they contain liquid cholesterol All are hyperintense on T1WI and heterogeneous signal intensity on T2WI and do not enhance The best diagnostic clue of a ruptured dermoid cyst is fatlike droplets in the subarachnoid cisterns, sulci, and ventricles . Extensive pial enhancement can be seen from chemical meningitis caused by ruptured cysts,Sagittal T1-weighted MR image shows mixed-signal-intensity lesion in the pineal region (straight arrow) with multiple hyperintense droplets scattered through the subarachnoid space (curved arrows). Moderate hydrocephalus is present. Ruptured dermoid cyst was confirmed at surgery.,Dermoid Cysts,Differential Diagnosis Epidermoid: typically resemble CSF (not fat), lack dermal appendages, and are usually located off midline Craniopharyngioma: suprasellar, with a midline location, and demonstrate nodular calcification. However, most craniopharyngiomas are strikingly hyperintense on T2-weighted images and enhance strongly,Dermoid Cysts,Differential Diagnosis Teratoma: usually occur in the pineal region Lipoma. demonstrate homogeneous fat attenuation and/or signal intensity and show a chemical shift artifact, which typically does not occur with dermoid cysts,Neurenteric Cysts,Pathologic Findings Congenital, benign, malformative endodermal lesions in the CNS Approximately three times as common in the spine, compared with the brain Most intracranial neurenteric cysts are found in the posterior fossa. Typically in the midline, anterior to