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.
A mega cisterna magna is thought to occur in approximately 1% of all brains imaged postnatally.
Especially if noted antenatally, a mega cisterna magna has been associated with
- 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.
The term was first coined by Gonsetteet al in 1968, in patients with cerebellar atrophy.
Differential is among other causes of an enlarged retro-cerebellar CSF space, including:
- arachnoid cyst
- epidermoid cyst
- cerebellar atrophy/cerebellar hypoplasia
- Dandy-Walker malformation