Cerebral syrinx with Chiari I malformation.

A 13-year-old female presented with acute left gaze paralysis. MRI revealed hydrosyringomyelia (HSM) with syringobulbia in the left pons extending cephalad into the centrum semiovale. A suboccipital craniotomy was performed and the foramen of Magendie was imperforate. Ocular movements normalized in 2 months and postoperative MRI confirmed resolution of the cerebral syrinx and syringobulbia and diminished HSM. This case represents an extreme example of the altered spinal fluid dynamics with Chiari I malformation. Theories on HSM are reviewed.