ARACHNOID CYSTS

ULTRASOUND

• CSF-like collection developing within the layers of the arachnoid membrane.
• Usually large.
• Unilocular.
• Smooth wall.
• Location:
• Cerebellopontine angle (majority).
• Related to vermis.
• Prepontine / interpeduncular cistern.

Video clip of posterior fossa Arachnoid Cyst.

• Communication with ventricular and perimedullary subarachnoid space.
• Morphologically intact vermis and cerebellar hemispheres. If large enough it may compress the vermis, cerebellar hemispheres and brainstem.
• May rarely extend through the incisura or foramen magnum.
• Hydrocephalus - 30-100% of cases (communicating or non-communicating).
• Locations:

1. Related to the inferior vermis.

2. Cerebellar pontine angle.

3. Quadrigeminal plate.

4. Prepontine.

5. Interpeduncular cistern.

REFERENCES

1. Langer B, Haddad J, Favre R et.al. Fetal arachnoid cysts: Report of two cases. Ultrasound Obstet Gynecol 1994;4:68-72.
2. Galassi E, Tognetti E, Frank F et.al. Infratentorial arachnoid cysts. J Neurosurg 1985;63:210-217.