Omnidirectional Saccadic Pursuit
- Cogwheel (jerky) pursuit eye movements in all gaze directions
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Common causes
- Viewed target is moved too fast by the examiner
- Patient inattention
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Uncommon causes
- Toxic/metabolic/neurodegenerative conditions
- Meningoencephalitis
- Increased intracranial pressure
- Cerebellar system dysfunction
- Small jerky eye movements (saccades) when following a target moving at < 30 degrees per second in any direction
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Trap: if you test pursuit by compelling the patient to follow a target moving at >30 degrees per second, you will evoke saccadic pursuit even in normal subjects!
- Brain MRI may be negative because the brain disorder is diffuse
- Impaired pursuit in aged, inattentive, uncooperative, tired, sedated, or sleepy patients
- Test pursuit by having the patient follow your finger or a light (a light is a more discrete target!) in all directions
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Trap: do not move the pursuit stimulus faster than 30 degrees/second because the normal pursuit system cannot keep up at that rate and saccades will be automatically substituted, even in individuals with a normal ocular motor system
- Omnidirectional saccadic pursuit can be a sensitive sign of brain dysfunction, but ...
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Trap: saccadic pursuit is most often due to patient sleepiness, inattention, poor cooperation, or poor examiner technique rather than brain dysfunction