Infratentorial arachnoid cysts

✓ A series of 20 cases of arachnoid cysts in the posterior fossa is reported. Classification was made according to the location of the cysts. Accurate clinical localization was only possible with cysts in the cerebellopontine angle. Ventriculography and pneumoencephalography were the most helpful investigations for making the diagnosis. Treatment consisted of suboccipital craniectomy and complete removal. There were four operative deaths. The remaining 16 patients had essentially complete recoveries.