Purpose: To determine which appearances on CT or MRI are indications for surgical treatment of intracranial arachnoid cysts.
Method: The images obtained from 26 patients treated either by surgery or conservatively were compared retrospectively. The features evaluated were the size of the cyst, evidence of a space-occupying lesion, cerebral abnormalities near the cyst and skull deformities.
Results: In 6 patients (23%), surgical treatment was indicated because of the presence of obstructive hydrocephalus. The presence of all other radiological findings did not differ significantly between the two analysed groups. 92% of the patients treated surgically benefited from the treatment. Fenestration and shunting produced similar results in respect to reduction in size of the cyst and the clinical and neurological symptoms.
Conclusion: The only indication for surgery is the presence of obstructive hydrocephalus. The other features were seen equally amongst the patients treated conservatively and the surgical patients and had no influence on the decision to operate.