ULTRASOUND OF SUPRATENTORIAL ARACHNOID CYSTS

• Usually single.
• Occasionally bilateral and symmetrical.
• More common in males and on the left hand side of the brain.
• Primary (abnormal development of the leptomeninges) or acquired (secondary to CSF entrapment within arachnoid adhesions post in utero hemorrhage, infection or trauma).
• Location.
• 50-65% in middle cranial fossa (near sylvian fissure).
• 5-10% in suprasellar / chiasmatic cistern.
• 5-10% in quadrigeminal plate cistern.
• 5% along convexities.
• 10-25% are infratentorial.
• Sonolucent, thin-walled cystic mass, with / without mass effect.
• No communication with the lateral ventricle.
• ± hydrocephalus (on an obstructive basis).
• 4th ventricle and vallecula are normal (in contrast to Dandy-Walker malformation).

Arachnoid cyst in the middle cranial fossa

Arachnoid cyst in the quadrigeminal plate cistern

Video clip of Supratentorial Arachnoid Cyst

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. Rachman S, Rachagan SP, Lim CT. Prenatal diagnosis of posterior fossa cyst. J Clin Ultrasound 1991;19:434-437.
3. Pascual-Castroviejo I, Roche MC et.al. Primary intracranial arachnoid cysts. Child's Nerv Syst 1991;7:257-263.