Locked-in syndrome

A neurological condition causing near-total paralysis while preserving consciousness, often after damage to the ventral pons. Vertical eye movements and blinking may remain available for communication.

Ventral pons: The front portion of the pons, a brainstem structure containing major pathways for movement. Infarction or injury here commonly interrupts descending motor pathways while sparing consciousness.
Coma: A state of prolonged unconsciousness in which a person cannot be awakened. Unlike locked-in syndrome, coma involves absent wakeful awareness.
Eye-tracking communication: Communication technology that interprets gaze direction to select letters, words, or commands. It can give people with locked-in syndrome a practical route to independent communication.
Basilar artery occlusion: Blockage of the basilar artery, which supplies blood to the brainstem and posterior brain. It can cause a ventral pontine stroke and produce sudden locked-in syndrome.
Corticospinal tract: A pathway carrying voluntary motor commands from the cerebral cortex to the spinal cord. Bilateral damage to these fibers causes profound paralysis of the limbs and trunk.
Unresponsive wakefulness syndrome: A condition with wakefulness but no consistent behavioral evidence of awareness. It differs because locked-in syndrome preserves awareness despite near-total inability to move.
Brain-computer interface: A system that translates brain activity into commands for an external device. It may provide communication when eye movements are too limited for gaze-based systems.
Pontine infarction: Tissue death in the pons caused by interruption of its blood supply. A bilateral ventral pontine infarction is a classic vascular cause.
Corticobulbar tract: A pathway carrying motor commands from the cerebral cortex to brainstem cranial-nerve nuclei. Its interruption can impair facial, speech, and swallowing movements in the syndrome.
Minimally conscious state: A disorder of consciousness marked by limited but definite signs of awareness. Behavioral responses may be sparse, whereas locked-in syndrome can conceal intact awareness behind paralysis.

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