Mega Cisterna Magna

MRI scan showing Mega cisterna magna
MRI scan showing Mega cisterna magna

A mega-cisterna magna, is a controversial entity among experts. In general however, the term is applied to non-pathological prominance (usually exceeding 10 mm in antenatal imaging) of the retro-cerebellar CSF space and not associated with cerebellar abnormalities. There is a normal vermis and normal cerebellar hemispheres.

Epidemiology

A mega cisterna magna is thought to occur in approximately 1% of all brains imaged postnatally.

Associations

Especially if noted antenatally, a mega cisterna magna has been associated with

  • infarction
  • inflammation and infection (e.g. Cytomegalovirus)
  • chromosomal abnormalities (e.g. trisomy 18)

Radiographic features on CT

Typically seen as prominent retrocerebellar cerebrospinal fluid (CSF) appearing space with a normal vermis and normal cerebellar hemispheres.

Legacy

The term was first coined by Gonsetteet al in 1968, in patients with cerebellar atrophy.

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Dandy-Walker malformation: (A, B)The fourth ventricle opens into a large posterior fossa cyst. There is associated hydrocephalus. (C) The cerebellum is hypoplastic & a thin rim of cerebellar tissue is seen forming the wall of the posterior fossa cyst (arrow). The vein of Galen, straight sinus, & venous confluence are elevated above the level of the lambdoid suture.

Differential diagnosis

Differential is among other causes of an enlarged retro-cerebellar CSF space, including:

  • arachnoid cyst
  • epidermoid cyst
  • cerebellar atrophy/cerebellar hypoplasia
  • Dandy-Walker malformation
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Burhan Ahmed is currently Editor-in-Chief at Medicalopedia.org. He completed his residency from Michigan State University in 2015. He has written three short revision books on Biology, Stomatology and Gynecology, has 4 publications to his name. He is pursuing career in cosmetic dermatology.

3 COMMENTS

  1. My wife is pregnant 9th month today checking the scanning some brain problem and doctors telling mega cistano magna 16m.m. But i don’t know please tell me anyone help me please

    • 16 mm is only significant if there are other fetal abnormalities. If your downes and trisomy screens were low risk and growth is ok (fetus size) then probably no medical significance

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