1、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
2、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 le
3、sions 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 FindingsOccur when lipid accumulates in the choroid plexus from
4、 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 (CPC
5、s),Choroid Plexus Cysts (CPCs),MicroscopicMicrocysts 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),CTIso- to slightly hyperattenuated on
6、nonenhanced CT scans compared with CSF Peripheral calcification is common Enhancement varies from none to striking,Choroid Plexus Cysts (CPCs),MRIIso- or hyperintense on precontrast T1-weighted MR images compared with CSF and show rim or nodular contrast enhancement Usually hyperintense to CSF on T2
7、WIThe 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 per
8、ipheral 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),Pathologi
9、c FindingsPial-lined interstitial fluid-filled structures that accompany penetrating arteries and veins, do not communicate directly with the subarachnoid spaceLocation: inferior basal ganglia, midbrain, deep white matter, and subinsular cortex. They can also be found in the region of the thalami, d
10、entate nuclei, corpus callosum, and cingulate gyrus,Enlarged PVSs,Pathologic FindingsMicroscopically, 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 typicall
11、y 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 sli
12、ghtly 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 show
13、s 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 hype
14、rintensity 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,Patholog
15、ic 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 cerebellumMost are incidental, but symptomatic cysts may manifest with headache, seizu
16、re, and/or obstructive hydrocephalus,Ependymal Cysts,Pathologic Findings Are thought to arise from sequestration of developing neuroectoderm during embryogenesisThey are thin walled and filled with clear serous fluid secreted from ependymal cellsColumnar cells, with or without cilia（纤毛）, line ependy
17、mal 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
18、). Signal intensity was isointense to CSF at all pulse sequences. Note lateral displacement of choroid plexus (solid arrow).,Ependymal Cysts,Differential DiagnosisCPC: are usually not identical to CSF at all imaging sequences, bilateral, and often enhanceArachnoid cyst: occur in the subarachnoid spa
19、cesNeurocysticercosis: hyperintense rim and scolex on FLAIR imagesAsymmetric 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
20、 is the most typical location , intraparenchymal neuroglial cysts are more common than extraparenchymal cysts,Neuroglial Cysts,Pathologic FindingsIntraparenchymal neuroglial cysts are congenital lesions, arising from embryonic neural tube elements that become sequestered within the developing white
21、matterThey 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,ImagingThe best diagnostic clue is a nonenhancing CSF-like parenchymal cyst with minimal to
22、no surrounding signal intensity abnormality The cysts are benign-appearing lesions with smooth, rounded bordersSize 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 ha
23、s 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 DiagnosisEnlarged PVS: multiple and cluster around the basal gangliaInfe
24、ctious cyst: typically smaller than 1 cm and can partially enhancePorencephalic cyst: communicate with the lateral ventricle and show surrounding gliosis Arachnoid cyst: typically extraaxial,Pineal Cysts,Pathologic FindingsOften with some residual pineal parenchyma Common: up to 10% of cases at rout
25、ine imaging and in 20%40% of cases at autopsy Three distinct layers: fibrous connective tissuepineal parenchyma with or without calcium finely fibrillar glial tissue that often contains hemosiderin deposits,Pineal Cysts,Pathologic FindingsOrigin : Ischemic glial degeneration, enlarged preexisting cy
26、sts,and enlargement of the embryonic pineal cavityUnilocular 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,Pinea
27、l Cysts,ImagingUnilocular fluid-filled mass within the pineal glandAttenuation or signal intensity varies with cyst content One-fourth have rim or nodular calcium in the cyst wallRim or nodular enhancement is also common 55%60% are slightly hyperintense to CSF On T1-WI. Most do not appear hypointens
28、e on FLAIR images60% 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 Diagn
29、osisPineocytoma: more likely to have solid components, but it may be impossible to distinguish the two with imaging studies aloneOther cysts in the quadrigeminal cistern that mimic pineal cysts include arachnoid cysts (no calcium) and, rarely, epidermoid cysts,Arachnoid Cysts,Pathologic FindingsBeni
30、gn, 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 structuresAre common, representing 1% of all intracranial masses. The
31、 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,ImagingSharply demarcated extraaxial cyst that can displace or deform adjacent brain Scalloping of the adjacent calv
32、arium often seen No identifiable internal architecture and does not enhance,Arachnoid Cysts,ImagingSame signal intensity as CSF at all sequencesOccasionally, hemorrhage, high protein content, or lack of flow within the cyst may complicate the MR appearanceIncreased prevalence of coexisting subdural
33、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
34、-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 DiagnosisEpidermoid cysts: Arachnoid cysts typically suppress completely on FLAI
35、R 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 DiagnosisChronic subdural hematoma: show CSF signal intensity on MR images and often have an enhancing membranePorence
36、phalic cyst : often follow a history of trauma or stroke. The cysts are normally surrounded by gliotic brain,Colloid Cysts,Pathologic FindingsBenign mucin-containing cysts More than 99% are found wedged in the foramen of Monro. typically attached to the anterosuperior portion of the third ventricula
37、r roof. The pillars of the fornix straddle the cyst,Colloid Cysts,Pathologic FindingsOther 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 r
38、apid clinical deterioration and even death ensue,Colloid Cysts,Pathologic Findings Derived from embryonic endodermSmooth and spherical, varying in sizeFilled with viscous gelatinous material Simple to pseudostratified epithelial lining The epithelial layer rests on a delicate layer of collagen and f
39、ibroblasts,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,ImagingThe location is at the foramen of Monro. Well-delineated hyperattenuat
40、ed mass on nonenhanced CT scansThe 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 c
41、olloid cyst at foramen of Monro (arrow),Colloid Cysts,Differential DiagnosisThe 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
42、 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 FindingsCongenital inclusion cysts The most common location is the cerebellopontine angle cistern , other place include the fourt
43、h ventricle, sellar and/or parasellar regions , cerebral hemispheres or brainstem, even extradural,Epidermoid Cysts,Pathologic FindingsAll are located off the midlineMost are asymptomatic but may result in mass effect, cranial neuropathy, or seizure Occasionally, epidermoid cysts rupture and may exc
44、ite a granulomatous meningitis,Epidermoid Cysts,Pathologic FindingsArise 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.,Epid
45、ermoid Cysts,Pathologic FindingsThe 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 (arr
46、ow) wrapping around basilar artery and displacing the brainstem posteriorly,Epidermoid Cysts,ImagingCSF-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,Epide
47、rmoid Cysts,ImagingCalcification is present in 10%25% of cases Most epidermoid cysts are isointense or slightly hyperintense to CSF on both T1- and T2WI, restrict on DWIMost do not enhance, although some minimal rim enhancement occurs in approximately 25% of cases,Epidermoid Cysts,Imagingwhite epide
48、rmoids”: 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
49、 diffusion-weighted image shows markedly restricted diffusion (arrows). Epidermoid cyst was confirmed at surgery.,Epidermoid Cysts,Differential DiagnosisArachnoid cyst: isointense to CSF at all sequences, displace rather than invade structures such as the epidermoid. Finally, do not restrict on DWIOther 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,
