Gaze-evoked nystagmus: a case report and literature review.

BACKGROUND: A sustained gaze-evoked nystagmus (GEN) is an important ocular finding that may indicate serious neurologic pathology. It is also a finding that can be missed easily during routine extraocular muscle (EOM) testing. This report presents a case that should familiarize the reader with GEN and presents a novel approach to testing EOM function. CASE REPORT: The mother of an otherwise healthy 4-year-old girl noted that her daughter's eyes crossed occasionally, the right lid drooped on one occasion, and she had been having strange headaches. An asymmetric, sustained, gaze-evoked nystagmus was detected using a different approach to EOM testing. Magnetic resonance imaging found a large, brainstem astrocytoma in the cerebellar-pontine angle. CONCLUSION: EOM function often is overlooked or underperformed but is an important part of the battery of clinical tests to rule out neurologic problems. Most forms of EOM testing will check for muscle palsies but little else. If the time is taken to extend the patient's gaze to the extreme ends, to attempt to hold the gaze in all 9 positions, and to maintain an accurate speed, the clinician can stand to gain much more information regarding the neurologic system.