The size of this normal fluid collection varies between people. Clinical significance of isolated mega cisterna magna. Dws malformation, dws mega cisterna magna and dws variant. On the sagittal t1 weighted image, there is absence of the inferior vermis with a large cystlike structure communicating between the cisterna magna and fourth ventricle. Mega cisterna magna is thought to be an anatomic variant with no clinical significance.
Mega cisterna magna refers to a normal variant characterized by a truly focal enlargement of the csffilled subarachnoid space in the inferior and posterior portions of the posterior cranial fossa. Distinction between dandywalker variant and mega cisterna magna in the fetus is difficult as definitive criteria have not been firmly established. The cisterna magna or cerebellomedullaris cistern is one of three principle openings in the subarachnoid space between the arachnoid and pia mater layers of the meninges surrounding the brain. The former condition should be suspected when a thin communication is found between the fourth ventricle and the cisterna magna, the latter when the cisterna magna has a depth greater than 10 mm. Nevertheless, the diagnosis of a cystic lesion of the posterior fossa often leads to difficult diagnosis and prognostic dilemmas. It is usually an incidental finding, and considered a normal variant, but it can also be associated with other anomalies, albeit rarely. There is a variable hypoplasia of the cerebellar vermis with or without enlargement of the cistern magna. It is an incidental finding on neuroimaging, and no imaging follow up is necessary. Dandy walker syndrome an overview sciencedirect topics. Mega cistern magna is a normal variant intact cerebellum and vermis but it may be associated with dandy walker syndrome, either full blown or a variant in which the vermis is absent. Related conditions include dandywalker variant varying hypoplasia of the inferior vermis without enlargement of fourth ventricle or cisterna magna, mega cisterna magna enlarged cisterna magna in the setting of normal vermis, and blakes pouch cyst extension of the fourth ventricle into the cisterna magna, represented by septae within.
For this reason, an indicative list of normal variants has been developed for each of the body systems with the exception of paediatrics. A mega cisterna magna, which some believe is due to cerebellar damage and volume loss, measures greater than 8 mm and is seen in 1% of postnatally imaged brains. The cistern space is present between the cerebellum, the dorsal surface of the medulla oblongata and the dura lining of occiput. This is most commonly visualized in the third trimester, and is less likely in the second trimester. A mega cisterna magna is essentially a brain that has filled with fluid. This either represents an arachnoid cyst of mega cisterna magna. It is therefore difficult to provide reliable parental counseling in. Mega cisterna magna is a normal variant, after careful assessment of. Cisterna magna is a normal retro cerebellar csf density space, when unusually prominent termed as giant cisterna magna. Csf and cerebellar symptoms in alzheimers, parkinsons and ms. A suboccipital puncture or cisternal puncture is a diagnostic procedure that can be performed in order to collect a sample of cerebrospinal fluid csf for biochemical, microbiological, and cytological analysis, or rarely to relieve increased intracranial pressure. Psychiatric manifestations associated with mega cisterna magna. The dandywalker variant is a milder form of the dandywalker complex and is characterized by normalsized posterior fossa, mild vermian. Rare case of dystrophia myotonica with mega cisterna magna.
A large one is called mega cisterna magna or giant cisterna magna. Mega cisterna magna is a normal variant, after careful assessment of the cerebellar vermis and fourth ventricle. Mega cisterna magna refers to a normal variant characterized by a truly focal enlargement of the csf filled subarachnoid space in the inferior and posterior portions of the posterior cranial fossa. Controversy remains around whether mega cisterna magna is a normal anatomical variant or. Psychiatric manifestations associated with mega cisterna magna swapna pandurangi, m. Dandywalker variant cystic posterior fossa mass with variable hypoplasia of the cerebellar vermis and no enlargement of the posterior fossa 3. It is a continuum of posterior fossa cystic abnormalities with varying degrees of vermian agenesis. Dandy walker dandy walker variant mega cisterna magna. Im not a neurosurgeon but i believe both are the same. Some practitioners also include another condition, mega cisterna magna mega meaning large, in the spectrum of dandywalker variant. This new classification facilitates both diagnosis and therapy of these disorders. A mega cisterna magna mcm is defined as a dilated cisterna magna whereas fourth ventricle, cerebellar hemispheres and vermis are normal1.
Controversy remains around whether mega cisterna magna is a normal anatomical variant or due to volume loss of the cerebellum. Dandywalker malformations are caused by dysgenesis dandywalker variant or agenesis of the cerebellar vermis and are associated with midline central nervous system abnormalities, including lateral and third. Mega cisterna magna and retrocerebellar arachnoid cysts. From the inside of the occiput to the back of the cerebellar vermis, the cisterna magna normally measures 2 to 10 mm. The second trimester genetic sonogram radiology key.
Dandywalker does not represent a single entity, as there are three identified types of dandywalker complexes. I also looked up mega cisterna magna, the normal variant that had been noted on the 2006 mri. For all the world it seems like the mega cisterna magna is a csf outflow deficit. Dandy walker dandy walker variant mega cisterna magna posterior fossa arachnoid cyst. We report a case of manic attack in a 23yearold man with mega cisterna magna. Anatomically, these four subtypes of dwc have their own unique characteristics 1, although they are regarded as a continuum in embryology 2. It lies between the cerebellum and the medulla oblongata. This syndrome has been described in association with schizophrenia, obsessivecompulsive disorder, manic episode, psychosis delusional type, and recurrent catatonia. Cerebellar hypoplasia and dandy walker malformations are to be ruled out in such cases. The following textbook is required reading for paediatric normal variants.
The prevalence and clinical significance of isolated mega cisterna magna in both fetuses and adults is not yet well defined. Mega cisterna magna is a condition in which the cisterna magna, the subarachnoid cistern below the fourth ventricle, is enlarged. Prominent cisterna magna is a result of degenerative disorders and requires no surgical therapy. There is nothing to suggest that the mega cisterna magna represents tissue damage of the mid brain or ventricular system. Psychiatric manifestations associated with mega cisterna. Revised classification of posterior fossa cysts and. Mega cisterna magna enlarged cisterna magna with normal cerebellar vermis dandywalker complex 3. It has been proposed to be due to a delayed rupture of blakes pouch rather than a failed rupture. It receives csf from the fourth ventricle via the median aperture foramen of magendie. Dandywalker malformation dwm or syndrome is a posterior fossa anomaly characterized by agenesis or hypoplasia of the vermis and cystic enlargement of the fourth ventricle causing upward displacement of tentorium and torcula. A mega cisterna magna refers to adult patients with significantly enlarged csf retrocerebellar cisterns in the posterior fossa with normal cerebellar morphology. The cerebellum is often affected in neurodegenerative diseases such as alzheimers, parkinsons and multiple sclerosis ms. Dandywalker complex dwc is a series of anomalies in the posterior fossa, including dandywalker malformation, dandywalker variant, mega cisterna magna and posterior fossa arachnoid cyst. Dandywalker syndrome dws is a congenital brain malformation involving the cerebellum note.
Atlas of normal variants that may simulate disease. This is distinct from and should not be confused with other posterior fossa cysts, such as arachnoid cysts and dandywalker malformations 8, 15, 16 fig. The openings are collectively referred to as the subarachnoid cisterns. It is done by inserting a needle through the skin below the external occipital protuberance into the cisterna magna and is an. Is a mega cisterna magma larger than a prominent cisterna. Mega cisterna magna is a part of dandywalker complex and it is characterized by the enlargement of the cisterna magna, morphologically intact vermis and cerebellar hemispheres.
The authors present two cases of mega cisterna magna associated with mania and catatonic schizophrenia. Dandy walker malformation statpearls ncbi bookshelf. This is usually an issue that is part of the bodys functioning after death, and relayed at the postmoterm exam. In children, other posterior fossa cysts are dandy walker variant, mega cisterna magna and arachnoid cyst. The cisterna magna is located between the cerebellum and the dorsal surface of the medulla oblongata. Mega cistern magna and arachnoid cysts show csf characteristics on various mri sequences. We report a rare case of type 1 dystrophia myotonica in combination with mega cisterna magna. Criteria for a definitive diagnosis of mega cisterna magna and dandywalker variant in the fetus have not been firmly established thus far. Dandywalker malformations are caused by dysgenesis dandywalker variant or agenesis of the cerebellar vermis and are associated with midline central nervous. On axial ultrasound, no communication will be seen between the fourth ventricle and the cisterna magna and the transverse measurement of the cisterna magna will be. Muscle coordination problems include disturbances in movements of the eyes such as nystagmus, as well as intention tremors and over shooting movements when attempting to do. The former condition should be suspected when the cisterna magna has a depth greater than 10 mm, 11 the latter when a thin communication is found between the fourth ventricle and the cisterna magna. Cisterna magna also called cerebellomedullary cistern the largest of the subarachnoid cisterns.
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