Acquired esotropia. A manifestation of Chiari I malformation.

A patient with acquired esotropia underwent apparently successful strabismus surgery. Subsequent recurrence of esotropia, associated with square-wave jerks and downbeat nystagmus led to further investigation. Although standard CT scan was normal, rescanning after instillation of metrizamide demonstrated a Chiari I malformation. Posterior fossa decompression alleviated the esotropia. Acquired esotropia has not been recognized as a manifestation of Chiari I malformation. Our case illustrates that a high degree of suspicion is required to make the diagnosis of Chiari I malformation. Specialized techniques, such as metrizamide cisternography, or magnetic resonance imaging may be necessary if routine diagnostic measures are unrevealing.