S Alandete, M Meseguer, CR Poyatos, D Uceda, E de la Via, J Sales, J Vilar. H.U. Dr Peset, Valencia (Spain)

Transcription

1 S Alandete, M Meseguer, CR Poyatos, D Uceda, E de la Via, J Sales, J Vilar. H.U. Dr Peset, Valencia (Spain)

2 Introduction Cystic lesions are usually a common finding in clinical practice and you can find in any diagnostic technique (ultrasound, CT and MRI) Understand and identify the different benign and malignant intracranial cystic lesions and review the radiologic appearance is important to make a correct differential diagnosis.

3 Normal variations: Cavum septi pellucidi and Cavum veli interpositi Cavum septi pellucidi: The septum pellucidum consists of two thin leaves of white matter surrounded by gray matter. The persistence of this septum after birth is called cavum septi pellucidi. It is between frontal horns and lateral ventricles. Cavum veli interpositi: Or cyst of the veli interpositi is localized between the lateral ventricles over talami, the internal cerebral veins flows inferiorly.

4 Normal variations: Cavum vergae and Megacisterna magna Cavum vergae: It is the persistence of the embryological fluid-filled space between the leaflets of the septum pellucidum. Mega cisterna magna: It is considered megacisterna magna when measured in the sagittal plane exceeds 10mm without involvement of the cerebellar hemispheres.

5 Normal variations: Dandy-Walker malformation This is a congenital anomaly characterized by the classic triad of hydrocephalus, absence or agenesis of the cerebellar vermis and posterior fossa cyst communicated with the fourth ventricle. Secondarily can cause hydrocephalus and intracranial hypertension.

6 Cystic lesions of development: Periventricular leukomalacia Periventricular leukomalacia is the necrosis of white matter with a characteristic distribution, external to the lateral ventricles involving the centrum semiovale that occurs in preterm infants less than 32 weeks. Ultrasound is the most sensitive technique to ischemia and shows hyperechoic areas. The control ultrasound reveals the formation of cystic lesions.

7 Cystic lesions of development: Periventricular cyst It is the result of incomplete formation of the lateral ventricle. It is always located adjacent the frontal horn. They may regress spontaneously.

8 Cystic lesions of development: Ventriculomegalia It consists in dilation of the ventricles due to hydrocephalus, it may mimic cystic structures. Linear ultrasound imaging transducer may be useful in identifying the thinned cortical hydrocephalus present and absent in the hydrancephaly.

9 Benign lesion: Arachnoid cyst They are CSF filled lesions, therefore they have the same intensity in MRI, which do not communicate with the ventricular system. It is the most common congenital intracranial cyst. It is the most frequent supratentorial cyst in the middle cranial fossa. It is a well-defined extraaxial cyst isointense attenuation with CSF. Scalloping of adjacent bone is a common finding is observed.

10 Benign lesion: Epidermoid cyst A common location is in the cerebellopontine angle. The radiographic appearance is similar to arachnoid cysts. Distinguishable characteristics are slightly hyperintense on FLAIR and diffusion-restricted.

11 Benign lesion: Dermoid cyst They represent 0.5% of all intracranial tumors. The majority are asymptomatic, symptoms only appear if mass effect and breakage. Locations vary according to the publications. The characteristics that differentiate it from the rest is its fat content observed as hypodense (fat density) on CT. On RM shows hyperintense on both T1 and T2 by the fat content.

12 Benign lesion: Neuroglial cyst Nonenhancing intraaxial CSF-like parenchymal cyst with no sorrounding signal intensity. May occur anywhere. The most characteristic finding is a cyst that follow CSF signal. The differential diagnosis must be made with arachnoid cysts and dilated Virchow-Robin spaces.

13 Benign lesion: Dilated Virchow-Robin spaces They follow CSF signal on all sequences. They have no enhancement or restricted diffusion. The differential diagnosis must be done with lacunar infarcts. They are pial lined interstitial fluid filled spaces that surround perforating vessels. They are common incidental findings. Their common sites are the basal ganglia (type 1), cortical gray matter (type 2) and midbrain (type 3).

14 Benign lesion: Colloid cyst They are cysts filled with mucin which gives a typical image. Almost 100% are in the foramen of Monro. The radiographic appearance is pathognomonic. On CT it is a well-defined hyperdense lesion. On MR it is hyperintense on T1 and isointense on T2 to the brain parenchyma.

15 Benign lesion: Choroid plexus cyst These cysts appears in the choroid plexus epithelium. The majority are asymptomatic and they are incidental findings. Most common in the atria of lateral ventricles. On unenhanced CT images is isointense to CSF and can show contrast enhancement, a finding that should not be confused with mass lesions in this location. On RM are hyperintense on T2 and 2/3 shows restricted diffusion.

16 Benign lesion: Miscellany Porencephalic cyst: These are cavities caused after infection, ischemic stroke, or surgery in the brain parenchyma. It follows CSF on MR sequences. Subependymal cyst: These are rare, benign cyst. More frequent intraventicular in the lateral ventricles. Most are incidental, if symptoms can appear, headache, seizures or obstructive hydrocephalus. The diagnostic clue is a cyst containing CSF with thin wall without enhancement.

17 Benign lesion: Miscellany Cyst of the anterior commisure: Receive their name to appear in this location. The anterior commissure is a fiber tract connecting the two frontal lobes in its basal part. On RM follows the same CSF signal. Choroid fissure cyst: This is well-defined nodular lesions typically located on the choroid fissure (between the fimbria of the hippocampus and diencephalon) On RM follows the same CSF signal, without restriction or enhancement.

18 Benign lesion: Miscellany Pineal cyst: Unilocular cyst located in the pineal gland which attenuation varies according to content. On MR it is slightly hyperintense to CSF and does not suppress on FLAIR. After contrast administration may show nodular or ring enhancement. The differential diagnosis is made with pineocytoma, imaging may be indistinguishable. Cyst of Rathke's pouch: These cysts arise from embryonic remnants of Rathke's cleft. The best imaging clue is a suprasellar cyst with a small intracystic nodule. MRI features are variable on T1 and hyperintense on T2.

19 Benign lesion: Miscellany Meningocele of the petrous apex: It is a rare lesion, corresponds to a herniation of the subarachnoid space from the posterolateral portion of Meckel's cave to the petrous apex. It is well defined hypodense lesions on CT and hyperintense on T2. Subdural hygroma: It is a CSF lesion that appears secondary to a subdural hematoma. The knowledge of the previous history gives us the diagnosis.

20 Infectious lesion: Neurocysticercosis Most neurocysticercosis cysts are in the subarachnoid space. Radiographic findings vary chronologically: Early vesicular stage: Smooth thin-walled cyst that is CSF-like on CT and MR images. A mural nodule is often present that represents the viable larval scolex, the cyst with a dot appearance. Colloidal-vesicular stage: Cyst fluid is hyperintense to CSF on MR images. Healing or granular nodular stage: nonenhanced CT scans show an isoattenuated cyst with a hyperattenuated calcified scolex. Quiescent or residual stage: Small calcified nodules. Multifocal lesions and lesions in different stages of development are common. Image courtesy of [1]

21 Infectious lesion: Hydatid cyst Cerebral hydatid cysts are rare. The most common location for intracranial hydatid cysts is the hemispheric parenchyma It is a single, large, thinwalled, spherical, nonenhancing CSFattenuation cyst in the parietal region of the brain Perilesional edema is usually absent. Image courtesy of [1]

22 Infectious lesion: Abcess Clinical patient is especially useful for diagnosis. Abscesses are characterized by low signal intensity on T1 and hyperintense on T2 and FLAIR with peripheral ring enhancement and restricted diffusion. The differential diagnosis is with primary tumor.

23 Tumoral lesions: Hemangioblastoma It is a vascular tumor that occurs in patients with syndrome of Von- Hippel-Lindau. Typically occurs in young patients in posterior fossa (95%). CT and MRI shows a cystic lesion with a mural nodule that enhances after contrast.

24 Tumoral lesions: Pilocytic astrocytoma It most often occurs in young patients and located in the cerebellum. It has a strong association with neurofibromatosis type 1. Radiologically large cyst with a mural nodule that enhances after contrast administration. On MRI it is iso-hypointense to brain parenchyma on T1 and hyperintense on T2.

25 Tumoral lesions: Central neurocytoma Rare tumour, less than 1%. Typically seen in young patients. A high percentage of these tumors are intraventricular located mostly in the lateral ventricles. On CT are usually hyperattenuating compared to white matter. Calcification and cystic regions are frequently present. On MR the main feature is cystic regions which are hypointense on FLAIR.

26 Tumoral lesions: Craniopharyngioma Typically arise in the sellar/suprasellar region. It is a cystic lesion with a solid minor component that enhance vividly on both CT and MRI. Calcification is very common

27 Tumoral lesions: Cystic meningioma About 10-20% of meningioma undergo cystic degeneration. The tumor has the same radiological features as meningioma, slightly hyperdense calcifications with intense and homogeneous enhancement after contrast administration with dural tail. On RM the cystic component is hyperintense on T2.

28 Conclusion Intra o extraaxial? Extraaxial Infratentorial Supratentorial Midline Off-midline Midline Off-midline Arachnoid cyst Epidermoid cyst Arachnoid cyst Pineal cyst Dermoid cyst Rathke cleft cyst Arachnoid cyst (convexity) Epidermoid cyst Arachnoid cyst (suprasellar)

29 Conclusion Intra o extraaxial? Intraaxial? Infratentorial Supratentorial Intraventricular Parenchymal Intraventricular Parenchymal Epidermoid cyst Enlarged perivascular spaces Choroid plexus cyst Ependymal cyst Colloid cyst Enlarged perivascular spaces Neural cyst Porencephalic cyst Connatal cyst

30 Conclusion There is a wide spectrum of organizations, knowledge of the radiologic features and its location allows us to narrow the list of differential diagnosis.

31 References 1. Intracranial Cysts: RadiologicPathologic Correlation and Imaging Approach Anne G. Osborn, MD Michael T. Preece, MD Radiology: Volume 239: Number 3 June Differential Diagnosis of Intracranial Cystic Lesions at Head US: Correlation with CT and MR Imaging Monica Epelman, MD Alan Daneman RadioGraphics 2006; 26: Posterior Fossa Malformations Karuna Shekdar, MD Semin Ultrasound CT MRI 32: Truex RC, Carpenter MB. Human neuroanatomy.6th ed. Baltimore, Md: Williams & Wilkins, 1969; Pauling KJ, Bodensteiner JB, Hogg JP, Schaefer GB. Does selection bias determine the prevalence of the cavum septi pellucidi? Pediatr Neurol 1998; 19: Born CM, Meisenzahl EM, Frodl T, et al. The septum pellucidum and its variants: an MRI study. Eur Arch Psychiatry Clin Neurosci 2004;254: Kwon JS, Shenton ME, Hirayasu Y, et al. MRI study of cavum septi pellucidi in schizophrenia, affective disorder, and schizotypal personality disorder. Am J Psychiatry 1998;155: Filipovic B, Prostran M, Ilankovic N, Filipovic B.Predictive potential of cavum septi pellucidi (CSP) in schizophrenics, alcoholics and persons with past head trauma: a post-mortem study. Eur Arch Psychiatry Clin Neurosci 2004;254: Bodensteiner JB, Schaefer GB, Craft JM. Cavum septi pellucidi and cavum vergae in normal and developmentally delayed populations. J Child Neurol 1998;13: Correspondence: Dr. Alandete salaiger@gmail.com