Figure 20a. Posttraumatic meningocele in a patient who had sustained a traction injury to the left arm and presented with weakness of the arm. (a) Posteroanterior chest radiograph shows a convexity at the left lung apex (arrow). (b) Axial CT scan obtained after intrathecal instillation of metrizamide demonstrates a posttraumatic meningocele extending through the left neural foramen (arrow).