Acquired esotropia due to Arnold-Chiari I malformation

Diplopia is not frequently associated with Arnold-Chiari I malformation. We reviewed our cases of Arnold-Chiari I malformation in which acquired esotropia with diplopia was the main neuro-ophthalmologic finding early in the clinical course.

Five patients were studied, all female, ranging in age from 17 to 36 years, who were treated by the neuro-ophthalmology service of urban teaching hospitals. Eye movement recordings using magnetic search coil technique were performed in two patients.

All patients reported onset of horizontal diplopia due to acquired esotropia as an initial manifestation of the Arnold-Chiari I malformation. All had full abduction of each eye. In addition, all five had gaze-evoked nystagmus, two skew deviations, and one bilateral internuclear ophthalmoparesis. Oculography in two patients showed normal abducting saccadic peak velocities. This supports divergence palsy as a mechanism of acquired esotropia and provides evidence against subtle sixth nerve palsy in these patients. Four patients underwent neurosurgical decompression of their Chiari malformations, and neuro-ophthalmologic signs and symptoms improved in all.

Acquired esotropia, often in association with other eye movement abnormalities, may be an early sign of Arnold-Chiari I malformation. This quantitative study indicates that divergence palsy is the cause of esotropia in some patients. Neurosurgical suboccipital and upper cervical decompression may lead to improvement or resolution of diplopia.