The abnormal pupil in Cheyne-Stokes respiration. Case report.

Cheyne-Stokes respiration commonly induces a rhythmic pupillary dilatation during hyperpnea and constriction during apnea. Failure of a pupil to dilate during hyperventilation indicates underlying sympathetic nerve paralysis. This report deals with an instance in which one pupil failed to constrict during apnea due to oculomotor nerve compression. The periodic respirations and anisocoria disappeared following surgical evacuation of a large ipsilateral subdural hematoma.