Arachnoid cyst with acute subdural hemorrhage

Findings

Large left frontal cystic lesion with thin septations and no enhancement. Unclear whether this lesion is intra-axial or extra-axial. No diffusion restriction (image not shown), no surrounding vasogenic edema. Also present is an acute right subdural hematoma caused by the patient's fall.

Differential diagnosis for the cystic lesion:
- Arachnoid cyst
- Ependymal cyst
- Glial cyst


Diagnosis: Arachnoid cyst. Acute subdural hemorrhage.


Key points

Arachnoid cysts are CSF containing cysts which are intra-arachnoid, and do not communicate with the ventricular system.
50-60% occur within the middle cranial fossa.
May arise as a developmental anomaly, or may be acquired as a complication of adhesions.
Small number are associated with neoplasms.
Walls of cyst are formed by splitting of the arachnoid membrane.
Usually asymptomatic. Can have headache or seizures.
The most effective surgical treatment appears to be excision of the outer cyst membrane and cysto peritoneal shunting.