A simplified approach to spontaneous eye movements in coma is:
- roving eye movements — metabolic/ toxic encephalopathy most likely, or although they can also occur with bilateral lesions above the brainstem.
- other ‘weird and wonderful’ eye movements — structural, metabolic or toxicological cause of comas.
- saccadic eye movements or fixing and following — pseudocoma (feigned coma).
Most individuals have a degree of exophoria when drowsy for any reason and any underlying strabismus tends to worsen — thus dysconjugate gaze is difficult to interpret in the stuporous or comatose patient.
TYPES OF EYE MOVEMENTS
Eye movements seen in the comatose patient include:
- roving eye movements —
Description: slow random predominantly horizontal conjugate eye movements (though there may be a degree of exophoria) similar to those seen in deep sleep.
Likely cause: metabolic encephalopathy (may be absent in deep coma), bilateral supranuclear lesions
- ocular bobbing —
Description: Rapid, conjugate, downward movement; slow return to primary position
Likely cause: Pontine strokes; other structural, metabolic, or toxic disorders
- ocular dipping —
Description: Slow downward movement; rapid return to primary position
Likely cause: Unreliable for localization; follows hypoxic-ischemic insult or metabolic disorder
- reverse ocular bobbing —
Description: Rapid upward movement; slow return to primary position
Likely cause: Unreliable for localization; may occur with metabolic disorders
- reverse ocular dipping —
Description: Slow upward movement; rapid return to primary position
Likely cause: Unreliable for localization; pontine infarction and with AIDS
- ping-pong gaze —
Description: Horizontal conjugate deviation of the eyes, alternating every few seconds
Likely cause: metabolic encephalopathy, bilateral cerebral hemispheric dysfunction; toxic ingestion
- periodic alternating gaze deviation —
Description: Horizontal conjugate deviation of the eyes, alternating every 2 minutes
Likely cause: Hepatic encephalopathy; disorders causing periodic alternating nystagmus and unconsciousness or vegetative state
- vertical myoclonus —
Description: vertical pendular oscillations (2–3 Hz)
Likely cause: Pontine strokes
- horizontal myoclonus —
Description: rapid horizontal pendular oscillations; the eyes appear to be shaking.
Likely cause: Serotonin toxicity
- monocular eye movements —
Description: Small, intermittent, rapid monocular horizontal, vertical, or torsional movements
Likely cause: Pontine or midbrain destructive lesions, perhaps with coexistent seizures
References and Links
- Posner JB, Saper CB, Schiff N, Plum F. Plum and Posner’s Diagnosis of Stupor and Coma 4e Oxford university Press, 2009.