Spinal cord herniation into an extradural arachnoid cyst.

A herniation of the thoracic spinal cord into the mouth of an extradural arachnoid cyst is reported in a 37 year old man. This is the 20th case, but the first posterior herniation; all the others were anterior. He presented with progressive paraparesis and the magnetic resonance imaging (MRI) showed kinking of the cord into the cyst. Surgical release of the neck of the hernia was successful. Copyright 2000 Harcourt Publishers Ltd.